P0380 on Mercedes-Benz: Causes, Symptoms and Fix Cost
Quick Answer
Safe to drive (short-term)
P0380 on a Mercedes-Benz is a diesel-only code meaning the engine control unit detected a fault in glow plug heater circuit "A" (the main glow plug circuit or its control relay). Glow plugs preheat the combustion chambers so a cold diesel can ignite. The ECU monitors the circuit for open or shorted wiring and a failed glow plug relay or module. Repairs typically run 60-400 EUR depending on whether a relay, wiring, or full plug set is needed.
- Severity
- Low · Electrical
- Typical repair cost, all makes
- €2-€480
Connect a standard OBD2 adapter (Bluetooth LE on iPhone) to your Mercedes-Benz and Skanyx tells you what P0380 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 P0380 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 P0380.
Mercedes-Benz (OM651 diesel)
2008-2018
The OM651 four-cylinder diesel uses a glow plug control module that the ECU monitors for circuit faults. P0380 on the OM651 is commonly the module or worn plugs. Mercedes glow plug data beyond the generic circuit code is manufacturer-extended and needs XENTRY or a Mercedes-capable tool. Plug access is moderate but the plugs can seize on neglected engines.
What causes P0380 on a Mercedes-Benz?
Beyond the generic causes listed on the main P0380 page, these are the patterns noted for Mercedes-Benz models:
Glow plug control module failure on OM651
: Mercedes-Benz (OM651 diesel)
Worn or seized plugs on neglected high-mileage engines
: Mercedes-Benz (OM651 diesel)
How to diagnose P0380 on a Mercedes-Benz with OBD2
- Read the stored code and freeze frame with Skanyx or any ELM327 adapter to confirm P0380 and note the temperature at which it set
- Check the glow plug system fuse and relay first, as a blown fuse or failed relay sets this circuit-level code
- With the ignition off and glow plugs disconnected, bench-test each plug with a multimeter: a healthy glow plug reads roughly 0.5-2 ohm, while an open (infinite) reading means that plug has failed
- Inspect the glow plug harness and connectors for corrosion, broken pins, or chafed wiring
- Verify the relay/control module sends battery voltage to the plugs during the preheat cycle with a multimeter on the supply side
- Note that per-cylinder glow plug live status is manufacturer-extended (Mode $22) data and is not available over generic OBD2, so the multimeter bench test is how you find the specific failed plug
How much does P0380 cost to fix on a Mercedes-Benz? (EUR)
Estimated repair costs for P0380 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 glow plug system fuse (DIY) | €2–€8 | €0–€0 | €2–€8 | Easy |
| Replace a single glow plug (DIY) | €10–€30 | €0–€0 | €10–€30 | Moderate |
| Replace glow plug relay/control module (shop) | €40–€180 | €50–€130 | €90–€310 | Moderate |
| Replace full glow plug set plus relay (shop) | €80–€260 | €90–€220 | €170–€480 | Professional |
Prices estimated as of October 2026. Costs vary by region, vehicle, and shop.
Codes related to P0380
These codes are often seen alongside P0380 or point to related issues, on any make:
Looking for the full P0380 reference (all makes, full diagnosis flow, complete repair cost matrix)? See the main P0380 guide