My DTCs, maybe just a bad ECU?

[Canyonero]

I'm getting four DTCs on my 3.4L swapped Isuzu Trooper, which has a swap harness made by Fuel Injection Specialties. They are:

DTC 68 - Air Conditioning Relay Shorted
DTC 82 - Ignition Control 3x Signal Error (crank position sensor)
DTC 53 - Battery Voltage High (overcharge)*
DTC 63 - Right Oxygen Sensor Error (Bank 1)*

With all these errors together, you think I might just have a bad ECU?

Air conditioning relay? Ok... This swap harness has no air conditioning wiring...

Low res crank sensor? Pretty sure it's plugged in, but I can double check...

Battery voltage high? I have an Optima Red Top battery, the charging is controlled by the Trooper chassis electronics. I haven't watched it with a voltmeter, but this code doesn't seem right. What is the overcharge voltage threshold anyway?

Bank 1 O2 sensor? I get this code when the truck is still open loop, is it missing the signal entirely? I don't doubt an O2 sensor problem, I get bad gas mileage. But I've swapped the O2 sensors on this a couple times already and yes I got a set of AC Delco.

*triggers CEL

[Canyonero]

So, I swapped to my other ECU which I've never used because it's for an auto. Well, turns out it works fine with my M/T. No rev limiting or anything I can tell (I ran it up to 5k RPM).

So, when I was fooling around with the other ECU at idle and a short drive, I got these five codes:

DTC 67 - A/C pressure sensor circuit error
DTC 53 - Battery Voltage High (overcharge)
DTC 25 - IAT, High Temp
DTC 44 - Left O2 Sensor, Lean exhaust
DTC 23 - IAT, Low Temp

So, WTF, another A/C error? I assume the IAT codes were because of my WAI. I was idling and have an electric fan so the underhood temps went up, then down considerably when I went for a test drive. Ambient temps were pretty low. Are the errors based on variance?

I swapped the O2 sensor and still got DTC 44.

Later in the day I took the truck for a longer drive and only got #44 with no CEL. Hmmmmmmm. Curious. I'll see what happens over the next tank of gas.

[IsaacHayes]

IAT sensor is either busted or there is an issue with the connections.... WAI won't cause both a low and high reading.... it won't throw any code. I would check your grounds first. Then check the harness for cuts/etc. Sounds like you have ground or connection problems on the connectors or something...

I'd swap back to the manaul ECM though, as the auto one might cause surging when slowing down to a stop.

[Canyonero]

I've gotten nothing but DTC 44 since that first test drive, which I still call an improvement over DTC 63. What do you mean by surging? I haven't noticed anything yet.

The ECU I was using is Serv# 16196742, now I'm running Serv# 16184737.

[bszopi]

Did you swap EEPROMs when you swapped ECUs? If so, then that's why you aren't having any issue, since the EEPROM is programmed for an manual.

[Canyonero]

No, these are '94-'95 ECUs. I didn't pop the cover off, but I thought they had onboard flash memory. I might take the first one apart and check the solder joints.

Also, would it matter that I don't have a VSS? Well, it's connected to the VSS within my cable-driven speedometer, but I'm not sure that's correct for the ECU. I never got any solid confirmation that it's 4000ppm analog, just assumed it was. I know it used a buffer to output 2000ppm digital for the old ECU.

[bszopi]

Ahh yeah, that's right. I forgot what ECM you were running... Disregard.

On an off-topic note... Post #6000 for me!

[Canyonero]

Good job.

[Canyonero]

Well, I think you guys are right. Truck is running worse on the A/T ECU. I'll swap the M/T back in there. I put in some work on the 1227727 harness last night, getting the unnecessaries striped out of that.

I haven't done much in tunerpro, I'm worried about that as there are NO BINS FOR THE 3.4L. I think I have tunerpro files for the 3400 and the 3.1L (but the 3.1L isn't DIS). I have no idea what I'm doing... Can anyone help?

[IsaacHayes]

3.1 RWD code will be great, only thing chagned from 3.1 to 3.4 rwd was DIS, and different intake manifold other than the .3L more displacement.

Basically, you'll use a code from something with DIS like a FWD 3.1, and then import in the fuel and spark tables from code from the 3.1RWD. You won't use the cam sensor or the 24x crank sensor behind the pulley. Just leave them disconnected or somethign.

[Canyonero]

You make it sound easy, but I still don't know how to do it.
ForcedFirebird claims the $88 code will work with DIS. I downloaded that.

Also, I called Nevada Speedometer (a lead from cardana24's jeep swap) about getting a VSS. Judy there knew her stuff. It's probably a couple weeks out still, but that should take care of some of my other problems.

[Canyonero]

Well, I shelved my 1227727 (Lumina) wiring for now because my friend's 3.4L came with a wiring harness and I already had a 1227727 ECU pigtail. I put some hours into cleaning up the 3.4L harness and deciphering all the loose ends. I grok that harness now and have everything figured out to splice it over to the 1227727 connectors. BUT, I might install it with the original '94 ECU first and see if that makes a difference, just ordered a VATS bypass for it. I fully intend to swap to the '7727, but maybe it would be better to do one thing at a time. Get my cam installed and broken in before I start messing around with the ECU conversion.