Voltage issue (92 12 valve)
#1
Voltage issue (92 12 valve)
Hey guys so I really don't have any luck with vehicles at all. Although this truck hasn't given me any issues till now after a couple years of owning. I'm having a voltage issue. I'm kinda assuming it's the internal voltage regulator in the pcm, but not 100%. Voltage is surging quite a bit, but not over its normal voltage only under and it's causing the tps/cps/overdrive to malfunction. Jumping back and forth from 3rd-4th gear. So my assumption is either the cps or the regulator. Getting kind of pissed off because my other truck(2nd gen) is already down and it's to cold up here in the north to be working on them.
#2
#3
Sadly after the 91.5 trucks they switched the regulator into the pcm instead of an external regulator which is on the 89-91.5 trucks. The only part of the transmission that's controlled by electronics is the O/D which is controlled by the Pcm and the tps. I have found out though that the Crankshaft position sensor can lead to issues with the Overdrive as well thats all the cps if for on these trucks. Charging and O/D.
#4
Sadly after the 91.5 trucks they switched the regulator into the pcm instead of an external regulator which is on the 89-91.5 trucks. The only part of the transmission that's controlled by electronics is the O/D which is controlled by the Pcm and the tps. I have found out though that the Crankshaft position sensor can lead to issues with the Overdrive as well thats all the cps if for on these trucks. Charging and O/D.
Im not sure if these 1st gen bodys are the same as newer ones in that they read voltage off drivers side and charge passenger side? I believe the PCM is located behind the drivers headlight in the fender but I might be incorrect on that, assuming im correct that would mean it reads on charges the other. Wouldn't hurt to run a jumper cable between battery posts to see if the issue is resolved that way indicating a poor crossover cable. Personally I had my alternator wire extended to charge the drivers battery, after boiling a new battery, I decided that wasn't going to happen again
#5
The major things to check with a voltage issue on these with a PCM controlled alternator is the cross over cable, battery connections in general for corrosion, tightness, cracks, ect. Next is a good clean connection for the alternator cable, next make sure all chassis, engine and body grounds are clean and solid. Wouldn't hurt to test the battery with truck running for A/C voltage indicating a failed diode trio. A/C voltage in a DC electrical/computer system does some wacky stuff
Im not sure if these 1st gen bodys are the same as newer ones in that they read voltage off drivers side and charge passenger side? I believe the PCM is located behind the drivers headlight in the fender but I might be incorrect on that, assuming im correct that would mean it reads on charges the other. Wouldn't hurt to run a jumper cable between battery posts to see if the issue is resolved that way indicating a poor crossover cable. Personally I had my alternator wire extended to charge the drivers battery, after boiling a new battery, I decided that wasn't going to happen again
Im not sure if these 1st gen bodys are the same as newer ones in that they read voltage off drivers side and charge passenger side? I believe the PCM is located behind the drivers headlight in the fender but I might be incorrect on that, assuming im correct that would mean it reads on charges the other. Wouldn't hurt to run a jumper cable between battery posts to see if the issue is resolved that way indicating a poor crossover cable. Personally I had my alternator wire extended to charge the drivers battery, after boiling a new battery, I decided that wasn't going to happen again
#6
have you actually tested he voltage with a multi meter to verify that it is dropping enough to cause it to drop out of overdrive? i would assume it jumping in and out of overdrive may likely be a completely separated issue like the temp sensor on the transmission line going bad. as long as the battery has 12v it should be enough to activate the overdrive solenoid. could also be a sensor issue. some people even swap to aftermarket transmission controllers. i got a friend with 2 of these trucks with overdrive on a toggle switch. if you think the voltage regulator in the computer is bad best to just install an aftermarket voltage regulator. they are easy to wire up.
#7
have you actually tested he voltage with a multi meter to verify that it is dropping enough to cause it to drop out of overdrive? i would assume it jumping in and out of overdrive may likely be a completely separated issue like the temp sensor on the transmission line going bad. as long as the battery has 12v it should be enough to activate the overdrive solenoid. could also be a sensor issue. some people even swap to aftermarket transmission controllers. i got a friend with 2 of these trucks with overdrive on a toggle switch. if you think the voltage regulator in the computer is bad best to just install an aftermarket voltage regulator. they are easy to wire up.
Last edited by BM9NBA2; 12-27-2021 at 11:46 PM.
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#8
have you actually tested he voltage with a multi meter to verify that it is dropping enough to cause it to drop out of overdrive? i would assume it jumping in and out of overdrive may likely be a completely separated issue like the temp sensor on the transmission line going bad. as long as the battery has 12v it should be enough to activate the overdrive solenoid. could also be a sensor issue. some people even swap to aftermarket transmission controllers. i got a friend with 2 of these trucks with overdrive on a toggle switch. if you think the voltage regulator in the computer is bad best to just install an aftermarket voltage regulator. they are easy to wire up.
#9
i don't think the crank position sensor should effect overdrive but it will effect the charging system if bad. it will not ground the asd if it doesn't sense that the engine is running. stupidly enough on the diesels all the asd relay does is power the alternator 12v field wire.
who said you have to always have to test for power at the battery? last time i checked there is many places in the cab that you can hook up a multi meter to check voltage while driving.
who said you have to always have to test for power at the battery? last time i checked there is many places in the cab that you can hook up a multi meter to check voltage while driving.
#10
i don't think the crank position sensor should effect overdrive but it will effect the charging system if bad. it will not ground the asd if it doesn't sense that the engine is running. stupidly enough on the diesels all the asd relay does is power the alternator 12v field wire.
who said you have to always have to test for power at the battery? last time i checked there is many places in the cab that you can hook up a multi meter to check voltage while driving.
who said you have to always have to test for power at the battery? last time i checked there is many places in the cab that you can hook up a multi meter to check voltage while driving.