Attention: TDR Forum Junkies A couple of days ago the "Check Gages" light came on after I had been driving a short distance. Found a P2502 (Charging System Error) code in the odometer window. I tried shutting off the truck and restarting. Each time the "Check Gages" light would come back on a couple of minutes after driving again. It was obvious that the generator was overcharging the batteries because I found some electrolyte on top of the passenger side battery. On one occasion I found electrolyte boiling out of the passenger battery immediately after engine start. The charging voltage at that time as checked with an accurate voltmeter was over 18 volts! I immediately shut it off and waited for a while.
I checked all wiring for good connections, etc. Truck was purchased new in Jan. 07 and only has 9K miles on it. No obvious corrosion, wiring breaks, loose connections, etc. Everything is very clean.
This should be a warranty issue but the only diesel tech at the local dealer is away at school for a week so I did some more troubleshooting. All the voltage & resistance checks from the service manual on the wiring and generator field resistance check out OK. I did not pull the plugs on the ECM and check the pin voltages. I drove the truck again the next day and everything seemed OK. Charging voltage is around 14. 6V. (That sounded high to me but a check of previous posts on this subject indicates that this is normal) No electrolyte boiling. No more codes yet. According to the manual the voltage regulation signal to the generator field coil comes from the ECM so there apparently is no voltage regulator built in to the generator. (It is called a generator by the manual, not an alternator). You can pull the field control plug off the generator and it stops charging, as it should.
This all leads me to believe that the problem is with the ECM. It sure seems like that would be a costly fix for a voltage regulation problem with the generator circuit. (Should be under warranty) Has anyone experienced a similar problem or have any other ideas??? It a'int fixed yet so I figure it will happen again.
Jim
I checked all wiring for good connections, etc. Truck was purchased new in Jan. 07 and only has 9K miles on it. No obvious corrosion, wiring breaks, loose connections, etc. Everything is very clean.
This should be a warranty issue but the only diesel tech at the local dealer is away at school for a week so I did some more troubleshooting. All the voltage & resistance checks from the service manual on the wiring and generator field resistance check out OK. I did not pull the plugs on the ECM and check the pin voltages. I drove the truck again the next day and everything seemed OK. Charging voltage is around 14. 6V. (That sounded high to me but a check of previous posts on this subject indicates that this is normal) No electrolyte boiling. No more codes yet. According to the manual the voltage regulation signal to the generator field coil comes from the ECM so there apparently is no voltage regulator built in to the generator. (It is called a generator by the manual, not an alternator). You can pull the field control plug off the generator and it stops charging, as it should.
This all leads me to believe that the problem is with the ECM. It sure seems like that would be a costly fix for a voltage regulation problem with the generator circuit. (Should be under warranty) Has anyone experienced a similar problem or have any other ideas??? It a'int fixed yet so I figure it will happen again.
Jim
