P037AGlow Plug/Heater Indicator Control Circuit Low
- Generic OBD-II code · Powertrain
- Turns on the check-engine light
- Matters for the ITP
- Needs a drive cycle to confirm a fix
- How the car detects it
- Diesel engines show the driver a wait-to-start lamp while the glow plugs preheat; the engine module switches it with a high-side driver. P037A means the lamp control circuit is too low – in practice a short to ground on the line to the instrument cluster. GM's diesels detect it in the driver itself: about 0.5 Ω to ground with the lamp commanded, only with a lamp configured, ignition on, more than 11 V and not while cranking. The 2015 engines need 3 s of fault, the 2016/2018 engines 10 of 15 samples; the check engine light follows after two trips. The glow plugs keep working; only the indication is missing, so the driver may start too early. CARB requires monitoring of the wait-to-start lamp circuit. Ford reports lamp faults under P0381 and does not use P037A.
- What you may notice
- Glow plug light does not come on or stays dim
- Check engine light on (GM after two trips)
- Driver starts too early, possibly poor cold start
- Likely causes
- LikelyLamp control wire chafed through to ground between engine module and cluster
- PossibleLamp or LED driver in the instrument cluster shorted internally
- PossibleMoisture or corrosion in the module or cluster connector
- RareDriver in the engine module faulty
- Inspection (ITP)
- Matters for the ITP. While the check-engine light is on, the car fails the emissions check.
- Repair
- Medium · Usually a job for a workshop.Typical cost: €60 – €400
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.