P0670

Symptoms

• Inability to start a diesel engine in cold weather
• The Check Engine light comes on
• Glow plug icon stays on or does not light up
• Excessive white smoke when trying to start in cold weather
• Unstable operation of the entire preheating system

Causes

• Open or damaged control circuit between the ECU and the GPCM module
• Oxidation or damage to the GPCM connector
• Glow Plug Control Module (GPCM) Malfunction
• No power or ground to GPCM
• Internal ECU fault

How to Fix

1. Read error codes with an OBD-II scanner, record all active codes
2. Inspect the GPCM module, wiring and connectors for damage, oxidation, breaks
3. Check the supply voltage and ground circuit of the GPCM
4. Check the control circuit between the ECU and GPCM with a multimeter for open and short circuits.
5. Check the presence of a control signal from the ECU at the GPCM input
6. If the circuit is working properly, replace the GPCM module; if the ECU is confirmed to be faulty, replace it

Related codes

Error P0670 by Vehicle Brand