P0670

What it means

The control circuit between the engine controller and the glow plug control module reports a fault. The ECU can no longer reliably command the module that drives the glow plugs, so cold-start pre-heating may not run. On a diesel this causes hard starting, white smoke, and rough running until warm. Causes: open or shorted wiring between ECU and glow plug module, a failed module, or a power/ground fault at the module.

Is it safe to drive?

The vehicle is usually drivable for short distances, but the problem can worsen or affect emissions. Diagnose and repair as soon as practical.

Most likely causes

• Glow plug control module faulty

  high

  One of the most commonly reported causes for this code — check this first.

• Wiring or connector fault

  medium

  A plausible cause — test and verify before replacing parts.

Related help

• Full P0670 diagnosis, causes & costs
• How to read check engine light codes
• Is it safe to drive with the light on?