Failed glow plug (most common, especially on higher-mileage engines); Damaged or corroded glow plug wiring harness or connector; Faulty glow plug control module (also called preglow control unit); Blown fuse or relay in the preglow circuit; Poor electrical connection at the glow plug or control module; Engine control module (ECM) software issue or internal fault (rare)

DTC codes / Mercedes-Benz codes / P1480

P1480 · Mercedes-BenzPreglow Control

Q: What does code P1480 mean?

Preglow Control. P1480 on Mercedes-Benz vehicles indicates a fault in the preglow control system, which manages the glow plugs used to warm the combustion chambers during a cold start. The engine control module (ECM) monitors the glow plug circuit and has detected an abnormality, such as an open circuit, short circuit, or a glow plug that is not drawing the expected current.

P1480 on Mercedes-Benz vehicles indicates a fault in the preglow control system, which manages the glow plugs used to warm the combustion chambers during a cold start. The engine control module (ECM) monitors the glow plug circuit and has detected an abnormality, such as an open circuit, short circuit, or a glow plug that is not drawing the expected current.

SystemPowertrain

Code typeMercedes-Benz specific

SeverityMedium

Fix difficultyIntermediate

AreaAuxiliary emission controls

Symptoms you may notice

Illumination of the glow plug warning light or check engine light on the dashboard
Hard starting or extended cranking when the engine is cold
Rough idle or misfire immediately after a cold start
White smoke from the exhaust during cold running
Often no symptoms besides the warning light, especially in mild weather

Common causes, most likely first

Failed glow plug (most common, especially on higher-mileage engines)
Damaged or corroded glow plug wiring harness or connector
Faulty glow plug control module (also called preglow control unit)
Blown fuse or relay in the preglow circuit
Poor electrical connection at the glow plug or control module
Engine control module (ECM) software issue or internal fault (rare)

How to diagnose and fix it

Scan all modules for stored codes and freeze-frame data to confirm P1480 and check for related glow plug codes.
Inspect the glow plug wiring harness and connectors for damage, corrosion, or loose connections.
Test each glow plug's resistance with a multimeter and compare to specification; replace any that are out of range.
Check the preglow control module for power and ground, and verify it is commanding the glow plugs on during a cold start.
Test the glow plug relay and fuse, replacing if faulty.
If all electrical components test good, check for technical service bulletins (TSBs) or software updates for the ECM.
Clear codes and perform a cold-start test to verify the repair.

Glow plug faults that fool even seasoned techs

A single failed glow plug can set P1480 on some Mercedes-Benz models because the control module monitors the total current draw of the circuit.
Corrosion inside the glow plug connector boot often causes intermittent faults that don't appear during a simple resistance test.
The glow plug control module can fail in a way that still allows the plugs to heat but sets a code due to incorrect current feedback.
P1480 is sometimes stored alongside glow plug-specific codes like P0670 or P0380, which can help pinpoint the faulty cylinder.
On certain models, a weak battery or charging system issue can cause low voltage during preglow, triggering P1480 without any glow plug fault.

Can I keep driving with P1480?

You can generally drive the vehicle, but cold starting may be difficult and prolonged driving with a faulty preglow system can lead to excessive white smoke and carbon buildup. Avoid heavy acceleration until the engine is fully warmed up, and address the fault promptly to prevent further issues.

Tools that help

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Guidance is general and written for Mercedes-Benz vehicles. Exact tests and values vary by model, so confirm the fault before replacing parts.