Vehicle Charging System Problem
PCM Wiring Issue On Dodge
93 dodge w250 diesel has charging problem.Replaces the alternator and the cps sensor reads good also the relays work fine.The truck wont charge while the wait to start light is on but after awhile it goes off and it starts charging, tried cleaned all ground connections and still it dont charge sometimes it takes a hour before the charging system kicks.Is it a bad pcm?
Troubleshooting Solutions For The Problem:
Yes It Seems Like Its A Faulty PCM:
- It does sound like you have a bad PCM. What would often happen with these SMEC type PCM's is they would partially power up when the key is first turned on but they wouldn't fully come alive and operate. If you're seeing the wait to start light come on for that amount of time and the charging system doesn't work then that tells me the PCM isn't fully coming alive.
Another Possibility Can Be Faulty Crank Sensor:
- How was the crank sensor tested? Internally shorted crank sensors did cause some problems on these, they could take the PCM down. It's suggested to unplug the sensor at the time the wait to start light won't go out, make sure the light doesn't go out. If it goes out as soon as the sensor is unplugged then you know the sensor is the issue.
Inspect Electrical Connectors And Ground Wire Connections:
- I would verify the PCM powers and grounds are good at the time it acts up. The best thing to do would be use a headlamp or fog lamp bulb and a couple jumper wires and if the bulb lights brightly this will ensure the circuits are capable of supporting a load.
PCM Wiring Test Details:
- You should have battery voltage on the dark blue wire in pin 9.
- You should have battery voltage on the red wire in pin 3.
- You should have ground on the black/tan wire in pin 11 and 12.
Why It Seems PCM Is The Possibility?
The flickering of the wait to start light and ASD relays and then the charging system starts working is a sure sign that the problem is internal in the PCM.
Try load test the powers and grounds when it is acting up to be sure, but what you are having is a common failure mode of a SMEC type PCM and replacing the PCM is going to be necessary.
Installing/ Replacing Voltage Regulator
If you didn't need or don't have an automatic trans, cruise control, speedometer or a/c then you can install an external voltage regulator and not worry about the PCM. A correctly installed and known good voltage regulator will allow it to charge, although if the PCM isn't working you wont be able to use the charging gauge/battery light in the dash to know that it is charging.
This Details Will Help.