Ecu question.

[Nickstjohn]

Hello all! I was recently given a non-running 89 4x4 van and have been restoring it. With lots of help from this forum I’ve got it up and running at last! During the process I discovered that the ecu is not original and came from an earlier model year. The part number on it is mostly illegible but it ends with a zero where as mine (89 automatic California 4x4) should end with a 1. Before I got the codes cleared it was throwing a 2 and an 11 which proved to be accurate, so clearly an 86-87 ecu. So here is my question! The van seems to be running perfectly. Is there any advantage to spending $300 for the correct ecu? Any disadvantage to going back to the stock ecu such as problematic ca emissions stuff? Any advice or wisdom would be greatly appreciated!

[AD2101]

I mean I would, there's parts of the EGR system and the downstream O2 sensor that the ECU isn't even recognizing if it's from an earlier year van. Also, has it passed smog like that?

With that being said, I have a couple of ECUs off of 4x4 Cali vans (89661-28091) I can part with for much less than $300. If you're interested, shoot me a PM.

[Nickstjohn]

Yeah, that’s the rub. It passed California smog in 2017 with the wrong ecu when my friends bought it. I have an appointment Wednesday to try to do that again to complete the transfer to my name. Either way though I see your reasoning, but am wondering if there’s some reason I’m not aware of that someone might have swapped them in the first place other than the original failing and then using what was available, which seems the most likely scenario.

[Gareth]

There's no computer interface hook-up for pre-96 vehicles, so if the emissions are still in range, it should pass SMOG again, if it did before like this. But, if the older ECU isn't recognizing parts of the system, then I could see the emissions more easily becoming out of spec.

[Nickstjohn]

Yeah, it also occurred to me that a check engine light on the dash will fail you even if they can’t pull the code or scan the system, or at least that’s my understanding, so if one of those sensors specific to 89 ca vehicles is acting up enough the throw a code but not enough to put the actual emissions out of spec it would pass with the wrong ecu but not with the right one. All conjecture at this point though! I’ll post how the smog check goes with the old ecu and then work from there!