Replaced my Glow Plug Control Module and harness's and still have trouble starting my truck unless the oil heater is plugged in. Not sure of the exact location of the PCM but I have DTC codes P0670 and P0683. From what I understand the P0670 can cause the P0683 so I may have started backwards. Help would be greatly appreiciated! Thanks!

 

P0683 — GPCM glow plug control modulecommunication line failure. Open/shorted circuit, failed GPCM, failed PCM

P0670 — GPCM Glow plug control module control line failure. Open/grounded circuit, open/shorted GPCM, failed PCM


Have you checked the glow plug relay by chance?

 

Mdub no I havent checked it. I do have H&S mini max so I do know what the codes are. Do you have a way to check the relay?