tb45e has no spark

[Off Tap]

Hello everyone,
I own a 98 nissan patrol which has the tb45e engine. The defect is I have no spark at the spark plugs. Whilst driving home one night the cars' engine started to surge but came good and I made it home- the next morning it would not start- engine cranks but does not fire.
I originally thought it was a fuel problem and have replaced the fuel pump and filters and I know I am getting fuel at the rail. When it did not start after this I did a spark test and found there was none- I have carried out the voltage and resistance checks on the distributor assy as per the nissan manual(DTC 21) and (DTC 11) and can not find any defects except that I can not get a pulse from the ecm to the distributor(although I only have a basic multimeter that does not read freq but it is showing 0 volts at the #1 pin on the distributor assy when cranking engine.
When I place a an led on the fuel injector harness and I bypass the fuel pump relay I get a pulse to the injectors which makes me think the camshaft position sensor is doing its job and the problem is with the ecm or nats.
The park/neutral position switch checks out ok and the only fault code showing before I deleted it was for a knock sensor.
I have checked power/ground circuits,fuses,relays,joint connectors with no defects.
The only other problem I can find is that battery voltage drops to 7 volts at ecm terminals 49,59 and 109 with everything connected.
Voltages at pins 57,58 and 43 show battery voltage.
The red light indicator for nats goes out as normal upon start.
It's an auto as well.
Anyone had something similar or any suggestions would be appreciated.
Cheers

[scottmeister]

With reference to page EC-73 of http://grosjean.pierre.free.fr/Y61%204,2/Service%20Manual/sm7e-1y61g1/ec.pdf

If you have 7 volts at ECM terminals 49, 59 and 109, yet the battery voltage elsewhere indicates 12+ volts, it seems to me that there is a likely short somewhere in the above circuit diagram: between the ECCS relay Terminal 5, ECU Terminals 49/59/109, CMPS and MAF. The LED cam position sensor or MAF will certainly not operate at 7 volts - the MAF becoming inoperative is indicated by the surging, a knock DTC may have been caused in the process of the MAF delivering erroneous readings. Have you followed the DTC-11 power supply and ground check procedure on page EC-74? You should also follow DTC-12 as the short could be in the MAF sensor circuit.

Once you have established no shorts in the harness, CMPS or MAF itself you should try to see if the ECU itself has a partial short on 49/59/109.

[Off Tap]

Hey scottmeister, I have followed those ground check procedures but I will do again and report my findings. I thinking a short as well- in regards to the ecu short do you mean inside the ecu itself- have you opened them up before ?
Thanks for the quick reply

[scottmeister]

A quick way to rule out the ECU: disconnect the ECU main harness, MAF and CMPS sensor connectors then manually activate the ECCS relay (by shorting its Terminal 2 to ground). Then, check voltage on ECM harness Terminals 49/59/109. If battery voltage, reconnect MAF and then CMPS connectors while checking each time. If everything is battery voltage and all good, I would say it must then be internal to the ECU (but I doubt this - I bet will be in the harness or MAF sensor). I've never pulled apart the factory ECU and I wouldn't bother either.

[Off Tap]

Okay I charged the battery overnight so values are slighlty higher, so,
1) with ECU plug off,MAF plug off and CMPS plug off,relay bridged- power at pins 109,49,59 is 12.6v.
2)ECU plug off, MAF plug on and cmps plug on, relay bridged-power at pins 109,49,59 is 12.6v.
3)ECU plug on,maf plug on and cmps plug on,relay bridged-power at pins 109,49,59 is 9.5v. Power at pins 57 and 58 show 12.6v with this configuration.
Whats weird is when measuring at pin 109-switching ignition on power spikes to 16v before settling at 9.5v.
Also confusing me is with everything connected and ECCS relay removed I get 12.6v at pins 1 and 3 but also 9.5v at pin 5 ?
What do you make of that ?

[Off Tap]

Right I sorted the back voltage problem which was making a mess of my fault finding. Scottmeister I continued with the plug pulling and found when I pulled the IACV-AAC valve harness connector the voltage at pin 109 dropped to virtually 0 and with that off I have zero volts at the MAF and CMPS which I am assuming the power(the 9.5v at relay pin 5)must have been coming from this faulty unit. The engine cranks so much harder now- still no spark as no power to 109 and co but at least I can start again with ground checks.

[scottmeister]

Sounds like the problem isn't the ECCS relay. Does it shut off a couple of seconds after you turn off the ignition?

I reckon the problem is in the harness - probably a joint connector somewhere. The only advice I have left is to follow the procedure from page EC-68 for power supply checking. As you are getting 12.6v at Pin 57 I think you can skip to EC-69 "H - Check Ground Circuit" --check for continuity between the given terminals and grounds, and if no worries there, then you'll need to look through the harness and look for shorts.

*edit* just saw you last post. It should have been obvious to me...9.5v is about what the idle valve will average when it's operating...I think there must be a short between that circuit to your ECU power supply/ground somewhere...!

[Off Tap]

Thanks Scottmeister, u have been a big help today- I shall continue with my quest !

[Off Tap]

Have been meaning to update this post for a while- I have sorted the problem. A few weeks back I came across a second hand factory ecu(same year and transmission) on ebay for $110. I was hesitant at first whether to fit it or not as I knew it would induce a NATS fault and if it did I would be another step back from sorting the defect. Eventualy I grew some balls and plugged it in and frig me dead the beast started- ran sweet for approximately 10 seconds and then died- started it again same thing, ran sweet for 10 seconds then died with engine light flashing. I didn't even bother checking the code as I knew it would be a NATS fault, the main thing was the spark was back and the main defect was solved- it was a bad ecu(it does happen).
So at least Nissan have allowed this logic for a part swap test to be carried out before pulling the plug on an unknown NATS part- for those who don't know NATS for the TB45e ST consists of your chipped key,the NATS immobiliser unit(which is a small box which sits on the back of the ignition barrell) and the ECU and these three components need to be registered with each other before you can drive your car without it stalling. Now when replacing one of these parts from original without reregistering it the system willl not work- at least not for more than 10 seconds max.
Now if you end up in this scenario- which by the way I am only vouching for an ECU change not changeing the other two NATS components you can take your vehicle to Nissan and have them reprogramme it(bet it would not be cheap) or if your in Brisbane you can ring Jonathon from Prime Locksmiths- 1300890540 and he will come to you with his advanced diagnostic equipment and reprogramme the ecu,immobiliser and key to match- as I said this is for an ecu change, I don't know if the immobiliser unit can be reprogrammed if you change that individually. Hope this info can be of use to some people.
Back on the road so happy days :)