Check engine light and fluctuating gauges

[94Reborn]

I just finished my 94 ranger swap. I have a 94 ranger with a 92 explorer 4.0, and the entire under hood wiring and ECM from a donor 94 ranger with the 4.0 stock. So all wiring was plug and play and nothing was spliced. The truck runs fairly well but has a slightly rough idle and a check engine light (which gives a code 111 for the first hard code group, then 3 stored codes, being 15, 71, and 58. 71 says cars only in my book, but is an ECM reinitialization detected on cluster control assembly. 58 is idle tracking switch circuit fault which I dont even know what that code is for. And 15 is the one I'm worried about most, power interruption to computer memory or pcm keep alive memory test failed.

Not sure if this is related, but also my oil pressure gauge jumps up and battery gauge drops on my gauges significantly when my headlights, wipers, ac, or any other load is put on the system.

My thought was possibly the voltage regulator on the alternator is failing and not getting enough power to the ECM or to the gauge cluster. However, the headlights still seem bright when turned on. I still need to check voltages to rule this out though. I thought maybe there was a ground issue also, so I have a ground from the battery negative to the frame, battery negative to starter bolt, and a ground from the frame to the drivers cylinder head. I changed the instrument cluster to see if that was the gauge issue, but the other cluster which I knew was working before, is doing the same thing.

Any suggestions where to start testing? Also, does anyone think the two problems are related or just coincidental? Any tips are appreciated, and thanks in advance.

 

[94Reborn]

I checked the voltages, I'm getting around 14.3 volts at the battery terminals with the engine running, even under load with headlights and blower on. 12.2 volts with the engine off.

 

[94Reborn]

33 views and nobody has any ideas...that's no good! I'm thinking I should try and check the KAM power wire and ground wires going into the ecm and the ground for the dash gauges. I found a pinout for a 2000 and a 1996 ranger 4.0 ohv, and I'm assuming the 94 pins are the same, so I guess I know which of those wires to check. Does anyone know where the ground is for the gauge cluster?

 

[holyford86]

All 4.0 engine computers output 3 digit codes, I'd run the test again

 

[94Reborn]

I don't think they output 3 digit codes, my code reader book lists 2 digit codes.

 

[holyford86]

They do, look in the tech library on this very site to find them

 

[American1990]

Did you find a answer to your problem?

 

[94Reborn]

I replaced the pcm with another from a 91 ranger 4.0. The codes are gone, however the gauges are still a bit touchy. That's something I can live with. But the 91 and the 94 ranger 4.0 computers both output 2 digit codes, not 3. A 11 code is system pass. It may be 3 digit in the newer obd-II trucks, but 94 and earlier are 2 digit.