TB42 Auto box Electricals?

[taslucas]

Hi, as some of may know i have been having issues with the lock out torque converter. It engages and disengages rapidly on the highway.

First i had a reco torque converter fitted, then a brand new Throttle position sensor.
This has been done by an auto specialist who has checked over the system.
Still got the same problem.
The mechanic now has the box apart and says its in really good condition, says it looks like it has recently been rebuilt. (ive not long had the patrol)

Mechanic now thinks it may be electrical: ECU or Road speed sensor.

Firstly, does anyone have any ideas?
And secondly how big a job is it to remove the dash and change the road speed sensor?
How much should a road speed sensor and ECU cost?

Missed out on having the trol on the road for the xmas break:(
Havent driven it much in the last 3 months!!!! Going CRAZY!!!

Thanks for any help:)

[jc58nc]

Does it drop out of lock on flat highway ? Or just when you hit a hill ? (Normal)
I have a 4.2 auto so I can compare yours to mine for you.
I used to have a Commodore ute auto that would drop back to third gear on the Hume Highway going to Melbourne while sitting on 110kms, that was normal :thumbup:

[taslucas]

Nah its on a flat highway. Definately not just normal kickback. It goes in out in out in out in out in out about as fast as youre reading that! and continues to do it until i either back right off and slow down (below 90 k's) or press the foot down and make it kick back properly.

[Bigrig]

Lock up solenoid???

[taslucas]

Lock up solenoid???

Cool thanks thats another to check.

[Bigrig]

Cool thanks thats another to check.

Sounds a bit odd, so what was said about the engine speed sensor? Also, like me, have you changed the coil lately by any slim chance?? Tachometer steady and not bouncy at all anywhere through the range?? You said you ruled out the TPS so that is about all I have based on the issues I've been having also ...

Good luck!!

[gq4200]

If you had another Instrument Cluster you could try and swap this.
The other thing I would do if you have some electrical know how would be to cut the wire from the Auto ECU to the Torque Converter Clutch (Lock - up) Solenoid. Pin 22 on the ECU. If you download the GQ Service manual in the downloads it is on page 469 (AT-62)... Looks like a Grey/Red wire if you look at the next diagram. This wire is the output from the ECU and turns on the Solenoid inside the Transmission to Lock the Converter. Once the wire is cut you can connect it to +12v whenever you want the Trans to Lock. Anything Over 80 km/h would be fine. This will tell you if the Transmission is faulty or the ECU is telling the Solenoid to turn off/on.
Another option would be to measure the voltage / connect a small lamp to this wire and watch what the ECU is commanding the transmission to do.

[NissanGQ4.2]

Hi mate, Is it the original valve body?

[gq4200]

I would also check the switch on the Transmission Lever. Have a play with the switch while it is locking/unlocking. This switch will lock/unlock the converter at speeds of over 95km/h.

[taslucas]

Hi mate, Is it the original valve body?

the gearbox was replaced about 4 years ago (got receipts with the vehicle). The box is out of the vehicle and in pieces atm, i called in and saw it this afternoon. My mechanic said that it has been rebuilt recently and so was looking very good inside (although the vehicle did not come with any receipts for this) Not sure if the valve body is the original one but it is standard. The gearbox is in great condition (the mechanic has just pulled it down and cleaned every little bit!) so that cant be the problem, The TPS is brand new so that cant be the problem, The torque converter is a reco one and only been fitted for about 500kms, All the fluid lines etc have been checked. So we are thinking it must be an electrical problem ie; speed sensor, ECU, or as Bigrig said maybe the lockout solenoid...... or something else.
Was thinking maybe get another ecu and swap to test?

[taslucas]

Sounds a bit odd, so what was said about the engine speed sensor? Also, like me, have you changed the coil lately by any slim chance?? Tachometer steady and not bouncy at all anywhere through the range?? You said you ruled out the TPS so that is about all I have based on the issues I've been having also ...

Good luck!!

Just thinking the speed sensor may be giving an erratic signal. Nah havent changed the coil, tacho only bounces as the torque converter locks then unlocks, locks then unlocks etc. Yeah TPS is ruled out.

Cheers

[Sir Roofy]

first thing that came to mind was electrical loose conections or faulty soliniode
then todd mentioned gear shift might just be the button again electrical

glad i went back to manual

[NissanGQ4.2]

Found this in the manual, sorta sounds like your problem

11914

Another thing I would check is the temp sensors on the valve body, when I had problems with my gearbox I found one of the wires on the temp sensor was broken.

[taslucas]

first thing that came to mind was electrical loose conections or faulty soliniode
then todd mentioned gear shift might just be the button again electrical

glad i went back to manual

Definately more things to go wrong in an auto, but its not common for patrols to have this much trouble. Bad luck i suppose. Auto's are great for Mud hills, Sand, Rock steps....everything except down hills and simplicity!!! lol
Very close to biting the bullet and fitted the extreme valve body while its apart..........But still will have to fix the problem

[Bigrig]

Definately more things to go wrong in an auto, but its not common for patrols to have this much trouble. Bad luck i suppose. Auto's are great for Mud hills, Sand, Rock steps....everything except down hills and simplicity!!! lol
Very close to biting the bullet and fitted the extreme valve body while its apart..........But still will have to fix the problem

Mate, I just installed that valve body, so when I get mine back and its actually running like it should, I can update on performance ...

And the downhill bit is more than solved with reduction gears - single best investment I've made (better than lockers for the amount you use them) ... mine crawls down hills now and if you get that valve body, you can get the manual torque converter lockup switch also and use it for engine compression down hill ... not as good as reduction gears, but a damn site better than standard.

[taslucas]

Found this in the manual, sorta sounds like your problem

11914

Another thing I would check is the temp sensors on the valve body, when I had problems with my gearbox I found one of the wires on the temp sensor was broken.

Thanks mate, i think ive skipped to steps 3 and 4 where it says: dissasemble A/T and check torque converter and oil pump.

[taslucas]

Mate, I just installed that valve body, so when I get mine back and its actually running like it should, I can update on performance ...

And the downhill bit is more than solved with reduction gears - single best investment I've made (better than lockers for the amount you use them) ... mine crawls down hills now and if you get that valve body, you can get the manual torque converter lockup switch also and use it for engine compression down hill ... not as good as reduction gears, but a damn site better than standard.

Yeah i think i am sold on the new valve body. Dont know about reduction gears tho, i like to floor it a bit sometimes!! But i look forward to hearing about the difference in your performance:)

[Bigrig]

Yeah i think i am sold on the new valve body. Dont know about reduction gears tho, i like to floor it a bit sometimes!! But i look forward to hearing about the difference in your performance:)

Looking forward to having it all tickety boo myself mate ... will update though ...

[taslucas]

Been talking to wholesale automatics they are nearly %100 certain that it is the temp sensor. I'm going to exchange the valve body for a extreme stage 2 and they will fit it with a new temp sensor. Fingers crossed it will fix the problem and be better than new!

[Sir Roofy]

hope so mate best of luck

[taslucas]

First time ive seen an auto completely apart........Wo!

[taslucas]

And apparently this is the trouble maker.....
Temp sensor.

[NissanGQ4.2]

First time ive seen an auto completely apart........Wo!

Haven't you seen my Gearbox rebuild thread??????: http://www.nissanpatrol.com.au/forums/showthread.php?5942-RE4R03A-Gearbox-Rebuild&highlight=gearbox+rebuild

Hope the temp sensor is the problem :):):)

I would of gone a stage 2 valve body but didn't have the spare dosh :( one day I will get one :):)

[taslucas]

Haven't you seen my Gearbox rebuild thread??????: http://www.nissanpatrol.com.au/forums/showthread.php?5942-RE4R03A-Gearbox-Rebuild&highlight=gearbox+rebuild

Hope the temp sensor is the problem :):):)

I would of gone a stage 2 valve body but didn't have the spare dosh :( one day I will get one :):)

Must have missed that thread. Was hoping to problem solve before going all out rebuild so didnt read the rebuild thread.
Thats great of you to post so many pics
The inside of them is rather "busy"!! You are a brave man! So you got it all back together and it works? lol i dont think i could pull that off!!
Seeing how mine has recently been rebuilt and in great condition, i have the cash to go for the stage 2 valve body. Cant wait!!

[NissanGQ4.2]

I'm not brave, my old man is an ex diesel mechanic by trade, I would not of attempted it without him :)

[taslucas]

Well, valve body is wrapped up and ready to send tomorrow. Probably wont see it by the end of next week (because of national pi55 up day, um i mean australia day and the definate friday off that everyone around the country will have LOL). But CANT WAIT WOOOOOO

[Bigrig]

Well, valve body is wrapped up and ready to send tomorrow. Probably wont see it by the end of next week (because of national pi55 up day, um i mean australia day and the definate friday off that everyone around the country will have LOL). But CANT WAIT WOOOOOO

Look forward to hearing the progress mate!!!

[NissanGQ4.2]

Look forward to hearing the progress mate!!!

x 2 :):):)

[taslucas]

I'm looking forward to feeling the progress! Will keep you posted:-)

[taslucas]

Valvebody posted 30 minutes ago. Hurry up hurry up hurry up........lol.

[WADS]

Hi Mate, I have had an experience with a GQ diesel auto that had an auto failure and wad rebuilt. after which the transmission would drop out of lockup. After much testing it was found that the engine wad running too cool. The lock up in this transmission is sensitive to the temperature of the transmission oil. Ensure that the return oil line to the transmissoin is connected to the drivers side of the radiator and not bypassed by having an external oil cooler fitted.
We found the engine cooling system thermostat to be the cause of this.
Hope this helps.
Wads, GQ maverick Auto.

[taslucas]

Hi Mate, I have had an experience with a GQ diesel auto that had an auto failure and wad rebuilt. after which the transmission would drop out of lockup. After much testing it was found that the engine wad running too cool. The lock up in this transmission is sensitive to the temperature of the transmission oil. Ensure that the return oil line to the transmissoin is connected to the drivers side of the radiator and not bypassed by having an external oil cooler fitted.
We found the engine cooling system thermostat to be the cause of this.
Hope this helps.
Wads, GQ maverick Auto.

Cheers mate ill look into that if the new tps, stage 2 valve body, reco torque converter, new temp sensor and rebuild don't work!! But damn I hope they do!!

[taslucas]

Valve body should be on its way mon/tue

[taslucas]

Hope you can zoom in to see that.

[ripper]

Any updates? Did the new valve body fix it?

[NissanGQ4.2]

Any updates? Did the new valve body fix it?

Ripper, update to his auto transmission drama's can be found in his members ride thread: http://www.nissanpatrol.com.au/forums/showthread.php?8643-Taslucas-s-TB42-Ti

The valve body wasn't the problem they just upgraded it while the gearbox was apart, and no they haven't fixed it yet problem is still there

Cheers

Todd

[ripper]

Thanks Todd.
After months of frustration with our auto, I recently found the problem, a broken wire that was intermittently playing up, so I can sympathise, and may be able to help here.

I don't have much time today, but I'll make myself known in the other thread, and see if I can think of any new possibilities.

[taslucas]

Cheers for that Todd.
I'd be interested in the broken wire info ripper. I've answered you in the other thread. If you've got any ideas it would be good to hear them in my members ride thread. Thanks in advance:)

tappn it

[NissanGQ4.2]

Thanks Todd.
After months of frustration with our auto, I recently found the problem, a broken wire that was intermittently playing up, so I can sympathise, and may be able to help here.

I don't have much time today, but I'll make myself known in the other thread, and see if I can think of any new possibilities.

Was the wire that was broken inside the valve body??? when my gearbox sh!t itself I found a broken wire inside the valve body which I believe was the temperature sender

[ripper]

I'd be interested in the broken wire info ripper.
I've written up the story at the end of my old thread here, but I'm happy to give more details if you want them.
Anyone rewired a rev sensor in a GQ automatic? (http://www.nissanpatrol.com.au/forums/showthread.php?4834-Anyone-rewired-a-rev-sensor-in-a-GQ-automatic&p=208934#post208934)


Was the wire that was broken inside the valve body???
It went to a solenoid on the valve body. The break was either inside the box, or outside within about 100mm of the case.

Edit:
I'll keep future comments for the other threads, it'll make the info easier to understand.

[ripper]

Okay, well I got a lot more net time than I expected today, so I've written my auto story and read yours.


Ok I did the self diagnosis this morning (5 times and once just then at lunch) it says the problem is: inhibitor switch, power shift switch, kickdown switch or idle switch circuit is disconnected or the control unit is damaged.
Anyone got any clues as to which it might be? Or which is the easiest to check? Haynes Book has info about inhibitor switch and power switch only.

Lucas

So your power light stays on after you change gears and press the power button on and off in the right sequence?

If so, you need to get a copy of page 41 and 42 of the AT section of Nissan's GQ workshop manual, it clearly explains how to test each of these components. No guesswork, just checking voltages at the TCU with a multimeter. It's a process of elimination.

I found this very tedious with our auto, but it was what led to fixing it.


on 26th March 2012 04:40 PM - Nothing comes up for an aftermarket sensor. Just found out its gonna be another 2 week's wait for the other temp sensor!
So in less than a week this should arrive?

[taslucas]

Yep, the new sensor should be here any day. I'll get that fitted and go from there.

I've had all the work done by an auto specialist.
First we fitted a reco TC.
No fix.
Then pulled the box completely apart to find it in really good condition. The guy said it looked like it had done less than 5000ks after a reco. He thoroughly checked every little part/wire/oil gallery.
While it was apart we fitted an aftermarket heavy duty valvebody.
(it was ment to come with a new temp sensor)
Fitted all back together.
Still no fix!
Found that the temp sensor hadn't been replaced. Replaced temp sensor with a second hand one.
Problem fixed!!!!...........for 6 weeks then came back.
I'm hoping that the second hand temp sensor failed (even tho it would be a coincidence) and that the new one (arriving soon) will fix the problem.
If not, then I'll check the TCU resistance.



tappn it

[ripper]

I'm hoping that the second hand temp sensor failed (even tho it would be a coincidence) and that the new one (arriving soon) will fix the problem.
That does sound like the most likely suspect, except that the error code doesn't match :mad:


If not, then I'll check the TCU resistance.

If it gets to this stage, I can probably help with explaining it more if necessary. For your code the tests start at the TCU with it still connected, for mine they started in the engine bay.

[taslucas]

Ok so I picked up the sensor....it was the wrong one:(.


Got them to get the right one...

Two more weeks go by.....

Picked up the correct sensor last week. Booked in to get it fitted (yes I'm lazy Todd! Lol).

Picked trol up this arvo.....

Yep......the new sensor hasn't changed a damn thing.....:(:mad::(:mad::(:(:(

Hmmmm what next?

Going to borrow a Mates TCU this weekend and try that. It's from a mav with a series 2 box? (has O.D button and HOLD button?) so would that be ok?

Wish me luck!

tappin it

[NissanGQ4.2]

Not sure if the TCU will work or not, I don't know if I personally would risk plugging in someone else's TCU unless it had the same part number on it.

I better go back to the start of this thread and have a long re-read

[ripper]

Yeah, I wouldn't be keen to put another TCU in unless it was an exact match.

If you have any thoughts of adding a manual toque converter set up, now may be the best time to do that. It'll let you isolate whether the problem is in the torque converter, or in the sensors.

I'm almost ready to post a thread with the whole story of my manual torque converter project, should be done very soon.

[NissanGQ4.2]

Should not be the TC as you have fitted a reconditioned one.

When you got the new valve body, did you also get new solenoids or did you use your old ones?

[ripper]

Should not be the TC as you have fitted a reconditioned one.

You're right, my bad.


When you got the new valve body, did you also get new solenoids or did you use your old ones?

It's not hard to test the circuit. Just undo the connector near the battery and measure the resistance between the correct terminal and earth.


I'm almost ready to post a thread with the whole story of my manual torque converter project, should be done very soon.

Done now My GQ manual torque converter lock up system (lotts-of-photos) (http://www.nissanpatrol.com.au/forums/showthread.php?11037-My-GQ-manual-torque-converter-lock-up-system-(lotts-of-photos))

[taslucas]

Should not be the TC as you have fitted a reconditioned one.

When you got the new valve body, did you also get new solenoids or did you use your old ones?

I was told by wholesale autos that a failing lockup solenoid was super rare and that it would be all good, so I assume they didn't change it.

Everything is brand new except for the solenoid for the lockup TC. So I'm thinking it must be that.

It can only be the lockup solenoid, speed sensor, some damaged wiring, or a faulty tcu.
The vehicle behaves as it should for the first half hour or so if driving.
If I go straight onto a highway I can drive for more than an hour without the problem happening. Then if I stop for 10 mins or so, when I get back on the highway, as soon as I get to 90k/h it starts playing up! So what ever is broken will work for a while then start failing. I thought it would have to be temperature related as nothing else changes while driving.

tappin it

[ripper]

I thought it would have to be temperature related as nothing else changes while driving.

I'm not so sure. Getting up to operating temp only takes about 10 min. These electronic boxes really can be temperamental.
Have you got a new error code since the temp sensor went in, to narrow down which circuit is the problem?

[taslucas]

I'm not so sure. Getting up to operating temp only takes about 10 min. These electronic boxes really can be temperamental.
Have you got a new error code since the temp sensor went in, to narrow down which circuit is the problem?

Yeah that's the thing though, I drive for about 15-20 minutes before I yet to the first 100 km/h straight. So the box should be up to operating temp. Get onto the straight, TC locks up, revs drop to around 1800rpm and all works like it should. Then after a bit more windy roads I get onto the highway, get up to 90 and the damn TC locks and unlocks rapidly......

As I've said, the most puzzling thing is if I'm parked near the hwy and start up and get straight onto the hwy I can sit on 90/100/110 for over an hour with all working fine but as soon as I stop for 5 minutes and go again, the problem appears ad soon as I get to 90.......


tappin it

[taslucas]

I'm not so sure. Getting up to operating temp only takes about 10 min. These electronic boxes really can be temperamental.
Have you got a new error code since the temp sensor went in, to narrow down which circuit is the problem?

Just checked the fault codes again, it's the same code, which is : "inhibitor switch, power shift switch, kickdown switch or idle switch circuit is disconnected or the control unit is damaged"

But I've got no idea how to check/fix any of these!

tappin it

[ripper]

Lucas, fixing this is going to be a real pain.

Do you have a copy of Nissan's workshop manual?

Do you have good skills with a multi meter, or a helpful auto electrician?

I've just been looking at which pages of the manual you're going to need, and it looks ugly already.

[taslucas]

Lucas, fixing this is going to be a real pain.

Do you have a copy of Nissan's workshop manual?

Do you have good skills with a multi meter, or a helpful auto electrician?

I've just been looking at which pages of the manual you're going to need, and it looks ugly already.

Lol, yeah it's been a pain already!

I got some instructions from wholesale autos on how to test the tcu with a multimeter but I'm not very confident at all in doing it. I also don't have much confidence in the auto electricians around here.

tappin it

[taslucas]

Are you talking about the manual that can be downloaded from this site?

tappin it

[ripper]

Lol, yeah it's been a pain already!

I was thinking that as I wrote it, but now it's going to take lots of testing, where as the shop's approach seems to have been 'throw money at it and hope for the best'.



I got some instructions from wholesale autos on how to test the tcu with a multimeter but I'm not very confident at all in doing it. I also don't have much confidence in the auto electricians around here.

tappin it

I ended up working out what was wrong with mine myself, when the automatic shop hadn't been able to, and the auto elect. said he couldn't do any more than what the auto shop could.

To sort this out you're going to need someone with multimeter skills. Is there and electrician (a domestic or industrial one I mean) in your area who can think outside the box? Some just shut down as soon as you mention anything to do with DC wiring.



Are you talking about the manual that can be downloaded from this site?

tappin it

Yes, that one, or a paper copy of it.

[taslucas]

I was thinking that as I wrote it, but now it's going to take lots of testing, where as the shop's approach seems to have been 'throw money at it and hope for the best'.



Not really. Everyone I have asked (including wholesale autos) has said
that it must be the TC, the tps or the temp sensor. So I have methodically changed those things one at a time. Another thing is that when the secondhand temp sensor was fitted, the problem went away instantly and completely for 6 weeks.....

I will go to all the auto electricians around here and have a good chat to see if any of them are willing to have a go....


tappin it

[ripper]

Not really. Everyone I have asked (including wholesale autos) has said
that it must be the TC, the tps or the temp sensor.

But your error code is saying
"inhibitor switch, power shift switch, kickdown switch or idle switch circuit is disconnected or the control unit is damaged"

Why weren't those eliminated first?

[taslucas]

First off the auto specialist test drove it and said the TC is stuffed, and it was so we replaced that, then he test drove again and thought it didn't feel right so had a closer look and found the tps was missing, then found it was missing because it had a carby off a manual in it so no place fir the tps. At that stage the error code was showing "problem with the tps circuit". Got another carby, fitted it with a new tps and the code went away but problem still there. Pulled box out to thoroughly check the internals, box was in awesome condition, auto specialist said it looked like it had dine less than 5000ks since a reco. Decided to fit a nomad valvebody while it was out. Put all back together, still had the problem but showing no error code. Tested temp sensor and found it was faulty. Put a second hand one in and the problem was gone completely (also no codes showing). 6 weeks later the problem came back and now showing that error code........ So I thought well maybe the second hand temp sensor had failed so I got a brand new Nissan genuine one fitted and still got problem.......



tappin it

[ripper]

Okay, makes more sense now. I didn't realise there was no error code earlier on.

Your box sounds as frustrating, or maybe even more frustrating, than what ours was. From the first time I pulled our box out (I did it twice, and the shop did it once as well), till it was finally fixed took more than 10 months.

I still think you need to get someone who's handy with a multimeter, and get them to trouble shoot the error code with the instructions in Nissan's workshop manual.


I will go to all the auto electricians around here and have a good chat to see if any of them are willing to have a go....

If that doesn't work, electricians, or electronics repairers, or maybe even someone who builds PCs, could do the job too.

[nissannewby]

Can you bypass the factory switch and put your own in for the tc lockup and see if this eliminates your gremlin?

[taslucas]

Can you bypass the factory switch and put your own in for the tc lockup and see if this eliminates your gremlin?

I reckon that could work if its not the lock up solinoid. But i really just want it to work properly, i hate patching things up. Its gotta be a fixable thing albeit ellusive at the moment!! Some things are just sent to test us!

[nissannewby]

With the switch idea it will rule out a harness problem can do this from diagnostic point of view just as a temporary to source the problem if it goes away with the switch bypassed then you could have a broken wire or something which is only playing up once warm etc weirder things have happened.

[pacs]

Hi taslucas I've also got an auto GQ though mines a little older 89 model tb4.2 and I've had a few heat issue with it but an similar issue to yours but this seems heat related and also related the the throttle position sender as when I get lockup it will stay no worries though when I push down a little further on the pedal to get a run up for a small hill or rise it flares similar to what yours has been doing though it only happens after around 50-80km of travel.. so after digging through the service/workshop manual I have noticed that my auto does not go through the radiator and is bypassing it straight for the external air cooler that's been added and I've just had my radiator re-cored from the standard two core to a three and I was wondering if you or anyone that owns an auto on here could advise on how much of a benefit I would see from reconnecting the auto through the radiator and then to the external cooler and also could you tell me or take a photo so I can see if its connected with metal pipe across the top and rubber across the bottom and what sort of pipe it is.
cheers pacs

[Ade]

Taslucas, any progress on your auto?

[Ade]

Hi taslucas I've also got an auto GQ though mines a little older 89 model tb4.2 and I've had a few heat issue with it but an similar issue to yours but this seems heat related and also related the the throttle position sender as when I get lockup it will stay no worries though when I push down a little further on the pedal to get a run up for a small hill or rise it flares similar to what yours has been doing though it only happens after around 50-80km of travel.. so after digging through the service/workshop manual I have noticed that my auto does not go through the radiator and is bypassing it straight for the external air cooler that's been added and I've just had my radiator re-cored from the standard two core to a three and I was wondering if you or anyone that owns an auto on here could advise on how much of a benefit I would see from reconnecting the auto through the radiator and then to the external cooler and also could you tell me or take a photo so I can see if its connected with metal pipe across the top and rubber across the bottom and what sort of pipe it is.
cheers pacs

Hi Pacs,

If you don't mind, what the atf temperature reads on your auto with out the factory cooler in the radiator?

Cheers,
Ade

[ckh]

Okay, well I got a lot more net time than I expected today, so I've written my auto story and read yours.



So your power light stays on after you change gears and press the power button on and off in the right sequence?

If so, you need to get a copy of page 41 and 42 of the AT section of Nissan's GQ workshop manual, it clearly explains how to test each of these components. No guesswork, just checking voltages at the TCU with a multimeter. It's a process of elimination.

I found this very tedious with our auto, but it was what led to fixing it.


So in less than a week this should arrive?

what was your fix? I've replaced the tcu no change, tried unplugging kickdown switch all that did was cause power light to flash several times when I started the car, powrr shidt switch is working fine, drops it back to 3rd when engaged havent tested inhibitor switch yet but got a second hand on on sunday and havent tested idle switch circuit yet, just cant get into diagnostic mode just get as far as power light staying on, which is error code "inhibitor switch, power shift switch, kickdown switch or idle switch circuit is disconnected or the control unit is damaged"

[ripper]

what was your fix?

Covered the whole drama of our auto here (http://www.nissanpatrol.com.au/forums/showthread.php?4834-Anyone-rewired-a-rev-sensor-in-a-GQ-automatic&p=208934&viewfull=1#post208934) but I'll try to give more help in a minute.

[ripper]

just cant get into diagnostic mode just get as far as power light staying on, which is error code "inhibitor switch, power shift switch, kickdown switch or idle switch circuit is disconnected or the control unit is damaged"

If this is all it will give you I'd start with that.
In the Nissan workshop manual it will give a process of elimination based on that result. I wouldn't bother trying to guess where the problem is, I'd just follow the manual step by painful step. I never would've found our problem any other way. None of the main components were faulty in ours, the problem was in the wiring itself.

I later damaged our tcu by putting 12 volts into it where it was meant to come out, but that has managed to reset itself, so the whole thing is great now.