Powertrain, generic · Ignition system or misfire

P037F Glow Plug Sense Circuit High

Check engine lightOn
EmissionsRelevant
Drive cycleRequired
Limp modeNo

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.

Likely causes

Sense wire chafed against positive or bridged in the connector
Glow relay sticking or output stage shorted (supply stays on)
Measuring circuit in the engine module

Symptoms

  • Check engine light on
  • Glow plugs possibly energised permanently (flat battery, plug damage)
  • Glow plug light implausible

Repair estimate

DifficultyMediumWorkshop job
Parts and labour€80–1,200
Time0.5–3 h

Typical range across vehicles; the real cost depends on what the testing finds.

Parts involved

glow plug supplyglow plug wiringengine control moduleglow plug relay

Related codes

P037DP037EP066BP0671P0670

References: gsi.ext.gm.com, gsi.ext.gm.com, law.cornell.edu.