Jeep Repair Problems? Ask a Mechanic for Answers ASAP
Hello I will help you with your question,
The green wire runs to the PCM and where it passes under the battery tray is a connector that is oftem corroded. This wire provides ground through the PCM which controls the current of the field coil regulating the output of the alternator.
Check continuity between the alternator connector and the PCM connector C2 pin #10 if this is a 2004 as posted above or PIN 20 if this is a 1994
Let me know what year and what I can do to help you with this
Ok the connector that I referred to is for the 1994.
If you attach a jumper wire to the green wire at the connector for the alternator and temporally ground it does the alternator charge? You can run a straigh pin in the back of the connector from the wire side and attach a jumper to it. Just ground it long enough to see if the alternator is charging
The white red wire should have battery voltage while the engine is running
Have you cleared the code?
The connectors are 1,2,3 black, white, grey
This is the pinout of the grey connector
You want #25, if you have to replace the wire I would check for power at the computer, clear the codes and then if there is power at the PCM but not at the alternator overlay a new wire cutting the old wire close to the connectors and soldering them in.
Check the battery temp sensor under the battery tray. There should be a continuious circuit between pin #15 in this same connector and #4 in the black #1 connector. About 1500 ohms would be good or at least a complete circuit.
The sensor will "tell" the PCM if the battery is too hot to charge or may be frozen and then it will not charge either. The sensor may be as much as 7000 ohms so be sure it really is open.
They don't give me a range so I have to think that the connection is poor and the PCM is reading too cold to charge the battery.
I would need a scantool to see what the PCM thinks the battery temp is.
If you had a resistor to put about 5000 ohms across the sensor connector that would tell if that is the problem.
I will look a little deeper to see if I can find a spec for the sensor but all the info is written with you having a scantool as the basis.
OK I will wait for your Hyundai to age!!
You can use a rheostat if you have one that you can adjust so it reads 5000 ohms or a 4700 ohm resistor is pretty common. I would just want to be about half of what the circuit reads right now.
I don't have a price for the temp sensor but it can't be that much, just be sure there is no corosion in the connector.
I think you are going to have to clear the code to tell the PCM that it is OK to charge the battery again, you can "borrow" a code reader from the autoparts store on a buy/return basis. Most of the stores have a tool program.
With a code reader you should be able to clear the codes and check to see if the field voltage is back so it will charge again. The PCM supplies both the voltage and the ground for the field of the alternator so it has to be convinced that it is OK to charge the battery.
Not the best design but it hasn't changed in 20 years.
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Let me know what you find and what I can do to help
#25 is the power to the field of the alternator so if there is no power the PCM has failed. I know you replaced it, I'm hoping you still have the original.
Install the original and see if you have a change in the voltage. Have you had any luck getting a resistor to substitute for the temp sensor? Something about 5K should be about right.
Does the scanner do anything more than read codes?
Maybe you have a charging voltage or battery voltage or en=ven better battery temperature data point?
You will have to have the engine running as the PCM does not turn the generator on until the engine is started and the idle is stable.
I see that the connector pinout lists a white/blue wire at pin#25 and the wiring diagram shows a white/red so that is the difference.
You will not be able to see data with that scanner but it is OK to get and clear codes with.
You can check the voltage at the alternator if you want, as long as you checked to be sure there is a wire between pin #25 and the alternator.
Let me know if you have voltage with the engine running then you can check for ground (one lead to the positive battery terminal, look for voltatge with the other lead) at the dark green wire
The charging system codes are two ignition codes so you will have to cycle it twice to have the code set.
OK the alternator is the only reading that you really need. If you have battery voltage there then you will be sure there is a complete wire between the PCM and the alternator and the PCM is supplying voltage. Next you would check for ground to the dark green wire.
Did you have any luck finding a resistor for the temp sensor?
I would install the new PCM plug in all the connectors and check the voltage at the alternator with the engine running and the pot in the temp sensor connector.
If you don't get voltatge to the alternator the PCM is no good.
Sorry but it does look like the PCM is bad.
I do know the source that you got your PCM from and I won't do business with them again. If you can get your money back I would.
The ground for the PCM is hard wired onto the circuit board and brought out on the grounds of the connector so the case will not affect this. I think you have a bad PCM and your original had failed as well. A new PCM from a reputable supplier should repair this issue.
I should have asked where you got it from first - sorry.
It is late and I need to be up early tomorrow so please excuse me.
Glad you stuck to it, I thought you found no power to the white/blue wire from the PCM so that is why I only mentioned checking the continuity and being sure the voltage made it from the PCM to the generator a couple of times.
I am glad you got it handled but I would use your original PCM if possible and return the junk (reman) one to Davie. I have seen the inside of those and I was an electronic tech in an eariler life so I would not trust it to last
Thanks for filling me in
With the transmissions they get power washed and a coat of silver paint to raise the price!
I heard on a financial planning show that 2 million have moved back in with their parents so be careful what you wish for.
Thanks again for letting me know the outcome
I know what you mean, I bought a junk house because it had a garage large enough to put a lift in because I drive junk and fix it rather than buy new!
Let me know if there is anything I can do for you in the future