P0670 on Mercedes-Benz: Causes, Symptoms and Fix Cost
Quick Answer
Safe to drive (short-term)
P0670 on a Mercedes-Benz 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.
- Severity
- Low · Electrical
- Typical repair cost, all makes
- €2-€370
Connect a standard OBD2 adapter (Bluetooth LE on iPhone) to your Mercedes-Benz and Skanyx tells you what P0670 means on that engine, whether it is safe to keep driving, and what the fix should cost. Free on iPhone and Android.
Get Skanyx freeWhat does P0670 mean on a Mercedes-Benz?
The Quick Answer above is the generic definition. What follows is the model-specific detail for the Mercedes-Benz models that log P0670.
Mercedes-Benz (OM651 diesel)
2008-2018
The OM651 uses a glow plug control module the ECU monitors for circuit integrity. P0670 here is commonly the module or its wiring. Mercedes module data beyond the generic code is manufacturer-extended and needs XENTRY or a Mercedes-capable tool. Verify supply voltage and ground before replacing the module on these engines.
What causes P0670 on a Mercedes-Benz?
Beyond the generic causes listed on the main P0670 page, these are the patterns noted for Mercedes-Benz models:
Glow plug control module failure on OM651
: Mercedes-Benz (OM651 diesel)
Wiring or ground integrity fault to the module
: Mercedes-Benz (OM651 diesel)
How to diagnose P0670 on a Mercedes-Benz with OBD2
- Read the stored code and freeze frame with Skanyx or any ELM327 adapter to confirm P0670 and note the conditions when it set
- Check the fuse feeding the glow plug control module, as a blown fuse can trigger the circuit fault
- Verify battery voltage at the module power supply pin and confirm a clean ground with a multimeter
- Inspect the connector and wiring between the ECU and the control module for corrosion, broken pins, or chafing
- 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
- 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
How much does P0670 cost to fix on a Mercedes-Benz? (EUR)
Estimated repair costs for P0670 in EUR, compiled across makes. Expect Mercedes-Benz parts and labour towards the upper end of each range.
| Repair | Parts Cost | Labor Cost | Total Estimate | DIY Difficulty |
|---|---|---|---|---|
| Replace control module fuse (DIY) | €2–€8 | €0–€0 | €2–€8 | Easy |
| Repair wiring/connector to control module (DIY) | €5–€30 | €0–€0 | €5–€30 | Moderate |
| Replace glow plug control module (shop) | €60–€220 | €60–€150 | €120–€370 | Moderate |
| Diagnose and repair control module wiring/ground (shop) | €10–€60 | €80–€180 | €90–€240 | Professional |
Prices estimated as of October 2026. Costs vary by region, vehicle, and shop.
Codes related to P0670
These codes are often seen alongside P0670 or point to related issues, on any make:
Looking for the full P0670 reference (all makes, full diagnosis flow, complete repair cost matrix)? See the main P0670 guide