gu idling too fast

[slapper]

Hi all, new to the site, quick hello and hope everyone is well. but to my problem. my sons 2001 3lt diesel all of a sudden began idling way to fast. any ideas as to cause?

thanks in advance

[Chaz]

Hi all, new to the site, quick hello and hope everyone is well. but to my problem. my sons 2001 3lt diesel all of a sudden began idling way to fast. any ideas as to cause?

thanks in advance

It could be caused by a number of things, but most commonly, the “HEAT” switch has been turned on. In some cases the TPS could be the culprit. If it’s only out by a smaller amount, it can be adjusted by a trimpot on the ECU that’s hidden behind a sticker or seal.