After starting up the truck and running it for a few minutes, the Check Gauges indicator lights up and the Voltage Gauge drops to 0. I put a scanner (Innova 3030) on it and it shows no DTC's set but the IM Monitor status shows some of the monitor's haven't run. Monitor's ON: Misfire, Fuel System, Comprehensive Component, Oxygen Sensor. Monitors's blinking (not running): Catalyst, Evap, Oxygen Sensor Heater. I left the ignition switch on for a long time and the blinking monitors never ran. When the engine is off the battery shows 12v. When the engine is running it still shows 12v though I expected 14v. When the check gauges indicator comes on the battery voltage goes up to 13v. At first I suspected an alternator problem, but the non-running monitors make me think I've got a PCM problem. I've got the Service manual which is not much help because it refers to the Powertrain Diagnostics Procedures manual which I don't have but have ordered. Has anyone had any experience with this problem or have any ideas about what may be causing it?

 

You have an electrical problem in there somewhere...... either the PCM, CTM, or the cluster itself.... if the engine will run, the volt gauge should never hit zero....... it's losing the data somewhere. Will your scanner tell you what the PCM thinks system voltage is?

 

No, it's an entry level scanner. Just the DTC's and IM's.