Savana Van engine light problem

Took the van in for routine inspection(Williamson County Texas means emission testing) and it failed. Normally; when you first turn the key on, the "service engine soon" light displays on the dash, then goes off when the engine starts. Well, mine did not come on when it should, at least not all the time. Seems that if the engine had been off for more than 5 minutes, it operated normally, but if cycled sooner than 5 minutes it would not.

So, the technician gets in the car in the parking lot, turns the key on for the first test, and it(the "service engine soon" lights up OK. He starts it, drives it into the bay, turns off the engine, hooks up the computer, and when he turns the key on the "service engine soon" light does not come on. This was repeated about 5 times, all similar results.

GMC had no record of this problem ever before???? There were no error codes stored in the cars computer, so Technician assumes bad onboard computer, so takes a chance and orders a new one. Plugs it in and everything is fine.

Has anyone ever experienced this kind of problem before? Sounds fishy to me.

Your missing info as to the year makes an answer here difficult ,also the pcms are warranteed for at least 7/70, by GM.

I have had years of experience fighting intermittent electronic problems on semiconductor manufacturing equipment and this sounds like a simple connector issue. I have resently had experience with my own service engine light soon issue. I noticed the automotive people now days like to sink the load to ground to turn it on a device. It is not uncommon to resolve an electronic issue by reseating a connector. My GMC has four connectors on the computer. Maybe reseating the connectors would have resolved your issue. I would have also recommended checking the continuity from the lamp to the computer connector. Probably to late to help you but maybe someone else might read this and have a light come on.

Good info here but this thread is 5 months old, please check that first, thanks.

Well, obviously have not checked in for several months, and have not seen the reply in April, sorry about that. You guys probably know much more than I do about my vehicle, except that is is over 200k, so no warranty. I do appreciate the input. I will be submitting a new post, regarding power steering.