Glow Plug Indicator (Diesel)
Informational — For your awareness
What It Means
This light has two functions on diesel engines: 1) Preheating: light is on while glow plugs warm up before starting (normal, wait until it goes out before cranking). 2) Fault: light stays on or flashes while driving — indicates a glow plug, glow plug relay, or engine management fault.
Common Causes
- Glow plug failure (individual plugs wear out over time)
- Glow plug relay / control module failure
- Engine management fault (flashing light)
- Wiring harness damage near glow plugs
- Cold start injector fault (older diesels)
Can I Still Drive?
Yes — the light during preheating is normal. If it stays on or flashes while driving, the vehicle is still driveable but may be harder to start cold and may have reduced power or increased emissions. Diagnose at next service.
Estimated Repair Cost
$80 – $600
This is an estimate only. Actual costs vary by vehicle make, model, year, location, and shop labor rates. Always get multiple quotes for major repairs.
Related OBD-II Trouble Codes
These OBD codes are commonly associated with this warning light. Scan your vehicle with an OBD-II scanner to get the exact code before diagnosing.