Engine/Transmission (1994 - 1998) What do I replace now ???

[PA95CTD]

I need help. The following items have stopped working on my truck. Tach, speedo, charging system, ac, fuel shut off soleniod. I first replaced the fuel shut off relay, didn't help. Next I cleaned all three grounding areas, didn't help. I just finished replacing the crank sensor, no luck. I set the sensor at . 050 like recommened. I'm getting tired of charging the batteries several times a week. Any other ideas?

 

[JoshPeters]

Charging system is the big one there. I believe the voltage regulator is inside the PCM and will not work till it sees an engine speed signal. I would get out your DVOM (digital volt ohm meter) and start checking wiring. I'd get a good wiring diagram, and check your power and ground wires. Don't just check for power, disconnect the batteries and ohm the power wire with itself and to ground. To ground you should see an open circut. If you come up empty handed after checking all your power and ground points (keep in mind the fuseable links and the circut 15 key on power to the PCM) I would lean towards the PCM.



Josh

 

[DSiemens]

Something is puzzling me. All the failures: a/c, tach, speedo, no charging and so on are common to the pcm except for the fuel shut off solenoid. Changing the crank sensor should have fixed the problem but it didn't, so it points to a pcm failure. Fly in the ointment is the fuel solenoid. If you have access to a frequency counter, the crank sensor outputs a signal (hertz) to turn pcm on.



Dan

 

[JoshPeters]

The more I think about it the more I think it's a power supply problem. I don't have a wiring diagram, so I can't pin point where the problem is. From a technician stand point, that is where I would look.



Josh

 

[PA95CTD]

Thanks for the replys, I remembered two more things that do not work, the grid heaters won't cycle, and the cruise won't work. When this all started, the truck was sitting in the driveway just idiling.

 

[JoshPeters]

Our engines produce alot of vibration. Idling it could have loosened something up, or somethign fineally let go.



Josh

 

[McCRam]

Every thing is run by the pcm except the fuel shut off solenoid. You should be able to take the pcm out of the truck and still start the motor. Maybe there is a common power source for the two. I would first check to see if you have power to the pcm and fuel solenoid. Did you check the fuses? I found that if I unpluged the crank sensor the pcm would turn on and the grid heater would cycle. I had a thread about the crank sensor and computer two days ago that was very helpful to me. I don't know if the wires will be the same color on the 95 as my 97 or not, but this was given to me in my thread. These wires are on the pcm.



circuit A22 (red/white) - dedicated 12v+ power from PDC fuse #8

A2 (lightgreen/black) - ignition 'on' 12v+ fused thru block #9

a31 and a32 (black/tan) - ground (test continuity to ground)

b10 (darkgreen) - generator driver (alternator turn on)

a8 (grey/black) to a4 (black/lightblue) - engine speed sensor (crank sense) - should have an ohm reading, or continuity. i think its a coil.

a17 (violet/white) - +5v feed to crank sense (should have +5v to ground when pcm on)



Hope this helps.

 

[PA95CTD]

I'll dive into it saturday and see where all of these great ideas lead me. It's raining right now, thanks to Ivan (2"rain over night). We don't need any more since Frances dumped 5" in a day and a half a week ago. My new garage will be started on monday (36x48x12). can't wait, no more laying in the dirt to change the oil. Thanks again and i'll post what i find.

 

[Howard Durand]

Has the ignition switch been replaced? There was a recall on them several years ago.

 

[PA95CTD]

No, that's never been replaced. It starts fine, just have to stall it to shut it down.

 

[vssman]

Remove & reinstall the connectors to the PCM. I had no charging after I had sealed a resistor for the transmission pressure input. Even though the connector was plugged, it didn't make good contact to 'turn' the charging system on.

 

[PA95CTD]

I'll try that also, Thanks.

 

[Sjester]

Alternator??

 

[shendren]

check the power wire pin 6 (purple) coming out of the pcm at the last connector inboard...