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Old 07-15-2007, 06:25 PM   #1
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Default 94 Alternator Not Charging / PCM Problem?

Didn't want to resurrect my old thread, so I'll start this one....

Quick recap: Got into an accident with my 93 SE, got a 94 SE good body/bad trans. Wanted to transfer good engine/trans from 93 to the 94.

Despite the differences between the 93 and 94, we already had the 93 engine pulled, and changing over a few things wouldn't be a big problem.

Things we changed:
Whole wiring harness from 94 onto the 93 engine.
EGR from 94 onto 93 engine.
AC Pres. Sensor from 94 onto 93.
We didn't change over the valvebody since all connections to the trans were the same.

We got the 93 engine/trans in and running.

Now the problem is the alternator is not charging, PCM is not signaling it to turn on. We tried:
Swap to the 94 alternator, still no charge.
Checked grounds
Have voltage all the way up to + on alternator.
Checked continuity between Pin L on alt connector to RB4 on PCM connector, checked ok
Voltage coming out of PCM to Pin L while running is .04V (should be around 12V?)


Both cars charged fine before the engine swap. We don't have a scanner to check for codes. Check engine light is not on though. It'* a 94 with the OBD-II connector, so checking flash codes isn't possible.

Any suggestions? Not sure if the PCM could have gone bad, since it was charging before the swap.


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Old 07-18-2007, 09:32 AM   #2
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My first suggestion would be check the wiring harness for any pinched or partially grounded wires. That'* quite odd.
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Old 07-18-2007, 07:33 PM   #3
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I just checked all the wiring and connections again, and it'* definitely not a wiring problem. I followed the connection from the alternator back to the bulk head, and was all clear. Checked for shorts from Pin L to all pins on bulk head and checked for ground to chassis. Then checked from the bulk head back to PCM connections. No shorts or grounds there either. The PCM is a Delphi remanufactured Service #16183247. I did a search and it looks like 94/95'* go through a lot of these. Anyone have any ideas before I go ahead and replace the PCM?

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Old 07-19-2007, 09:18 AM   #4
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You are thinking that the PCM isn't requestiing the correct voltage, correct?

I would run the alternator (new or not) down to the parts store and have them test it out. it'* typically free and that will help you rule it out completely.

We've seen odder things from PCM'* and seem to be noticing a rash of them going bad lately. It could be...although if it'* not exhibiting other funky symptoms..I may be hesistant to spend the money.

I've got a tested spare here if you want to give it a try for the cost of shipping.
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Old 07-20-2007, 06:08 PM   #5
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I borrowed a scantool today and got these codes:

640 QDM 1 Failure
650 QDM 2 Failure
325 Esc Failure
630 I didn't write down the exact message, but it had to do with voltage out of range.

The weird thing is, with the scantool connected, the voltage is at around 17V. So it actually starts charging, but the PCM isn't controlling it properly. With the scantool disconnected, it goes back to not charging at all.

Any ideas? With two QDM failures, could it be the PCM is shot?


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