P0670: Glow Plug Control Module Circuit

P0670 is a diesel-only code meaning the engine control unit detected a fault in the glow plug control module circuit. The control module switches high current to the glow plugs that preheat the combustion chambers for cold starting and reports back to the ECU. The code points to the module itself, its supply or control wiring, or its ground rather than to one specific plug. Repairs typically run 70-350 EUR.

P0670 is a electrical-related diagnostic trouble code classified as low severity. When your vehicle's ECU detects this condition, it stores P0670 and illuminates the check engine light.

If your vehicle has triggered P0670, you may notice one or more of these symptoms:

• Check engine light or glow plug indicator illuminated
• Hard or extended cranking on cold starts
• White or grey smoke from the exhaust when starting cold
• Rough idle and misfire during the first minute after cold start
• Glow plug warning lamp flashing on some vehicles
• Will likely fail a diesel technical or emissions inspection

Here are the most common causes of P0670, ranked by how likely they are to be the culprit:

Generally yes, for short-term driving. Safe to drive once the engine is warm. The glow plug control module only matters for cold starting a diesel, so the engine runs normally after warmup. Expect harder cold starts, longer cranking, and more white startup smoke. The car will likely fail a diesel inspection with this code stored.

Follow these steps to pinpoint the root cause of P0670:

1. Read the stored code and freeze frame with Skanyx or any ELM327 adapter to confirm P0670 and note the conditions when it set
2. Check the fuse feeding the glow plug control module, as a blown fuse can trigger the circuit fault
3. Verify battery voltage at the module power supply pin and confirm a clean ground with a multimeter
4. Inspect the connector and wiring between the ECU and the control module for corrosion, broken pins, or chafing
5. Bench-test the glow plugs themselves with a multimeter (a healthy plug reads roughly 0.5-2 ohm) to rule out a dead plug dragging down the circuit before condemning the module
6. Remember that detailed control module and per-plug status is manufacturer-extended (Mode $22) data that generic OBD2 does not expose, so module replacement is confirmed by supply, ground, and wiring checks plus the plug bench test

Repair costs for P0670 vary depending on the root cause and your vehicle. Here are typical estimates:

P0670 behaves differently depending on your vehicle. Select your car below for model-specific causes, known issues, and adjusted cost estimates:

These codes are often seen alongside P0670 or indicate related issues: