P037FGlow Plug Sense Circuit High
- 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
- P037F means the voltage read back from the glow plug supply is too high. GM's 2016/2018 diesels set it when the feedback lies above a threshold derived from the run/crank relay voltage, with a feedback above 5.0 V – for example voltage is reported although the plugs are not energised, or the sense line is shorted to positive. The code needs 40 of 80 samples at 50 ms, about 2 of 4 s, only with the engine running, and turns on the check engine light after two trips; GM classes the cause as internal to the module. If there is a real short to positive or a stuck relay or output stage, the plugs can stay energised permanently, overheating them and draining the battery – then also check the single plug codes P0671 ff and P066x. CARB requires glow plug circuits to be monitored for correct current and voltage drop.
- What you may notice
- Check engine light on
- Glow plugs possibly energised permanently (flat battery, plug damage)
- Glow plug light implausible
- Likely causes
- LikelySense wire chafed against positive or bridged in the connector
- PossibleGlow relay sticking or output stage shorted (supply stays on)
- PossibleMeasuring circuit in the engine module
- 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: €80 – €1,200
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.