jimbo486

a friend of mine has his truck at the shop. '00 year truck. the ECM is only putting out 6.5v before the relays for the grid heater. the only code they've found is P0381 which i found to be "Glow Plug/Heater Indicator Circuit (Wait To Start Lamp Inoperative)"

could an inoperative WTS light cause low voltage from the ECM? he's fearing he needs a new ECM but hopefully it's not that bad. what can you guys tell me? i'm not too familiar with the 2nd gen 24v motors. TIA!!

patdaly

Pretty sure 00 was still pull to ground for the Grid Heaters, should be no voltage.

Check it out.

jimbo486

can you elaborate on the "pull to ground" for the grid heater? i'm not understanding what that means. where should there be no voltage?

patdaly

Pull to ground means the solenoid is hot, and the PCM brings the solenoid to ground to actuate. I am pretty sure they changed it to supply 12V from the PCM to the GH solenoid in 2001.

Should be no voltage on the PCM leads if I am right.

dozer12216

ECM provides power to each control relay. Relay contacts close and provide power to grid heaters in programmed sequence. Control circuit of relays is permanent ground so voltage measured on ecm side only when ecm operates.

patdaly

Dozer, what year did they switch, I was always told is was 2001?