Glow Plug Module Control Circuit More details
The glow plug control module isn't communicating properly with the engine computer, like a dimmer switch that's broken and won't respond to commands. This prevents the glow plugs from heating the engine cylinders before a cold start on diesel engines.
The ECU monitors voltage and current signals from the glow plug control module during the glow plug pre-heating cycle. It checks for proper circuit continuity and module response when commanding glow plugs on. If the module fails to acknowledge or draw expected current, the fault is logged.
| Parameter | Normal Range | Fault Condition |
|---|---|---|
| Glow plug control module voltage | 12-14V with proper response to command | No voltage response or open/short circuit detected |
| Glow plug current draw | 15-100A during pre-heat cycle | Zero amps or excessive draw indicating circuit failure |
Code P0670 is a moderate fault. You can generally drive to a workshop, but avoid long trips or high-load driving (motorway, uphill towing) until it is diagnosed. If the code keeps returning after clearing, or if you notice the symptoms listed above worsening, do not delay professional diagnosis. Many moderate codes have multiple possible root causes — a mechanic with live OBD data can identify the exact fault more efficiently than part-by-part trial and error.
Once the fault is repaired, P0670 can be cleared using any OBD-II scanner. Connect the scanner, navigate to "Clear Codes" or "Erase DTCs," and confirm. The check engine light turns off immediately.
The code will return if the root cause was not actually fixed. The ECM re-detects the fault within 1–3 drive cycles and sets the code again.