Powertrain, generic · Ignition system or misfire

P037E Glow Plug Sense Circuit Low

Check engine lightOn
EmissionsRelevant
Drive cycleRequired
Limp modeNo

P037E means the voltage read back from the glow plug supply is too low. GM's 2016/2018 diesels, whose glow plug output stages sit in the engine module, compare the feedback with the battery voltage while glowing: if it is lower by more than a calibrated, current-dependent threshold – excessive voltage drop or a short to ground of the sense line – a sample counts as faulty, and 60 of 120 samples in a 50 ms grid set the code, roughly 3 of 6 s. The check only runs with the engine running (afterglow), not while cranking, and is suspended if a single plug or the supply already has an electrical fault. GM classes the cause as internal to the module (measuring circuit) and turns on the check engine light after two trips. There is no limp mode; glow plug monitoring is restricted.

Likely causes

High contact resistance in the glow plug supply (connector, ground, fusible link)
Measuring circuit or output stage in the engine module
Sense or supply wire shorted to ground
Weak battery or vehicle voltage at the edge of the enable range

Symptoms

  • Check engine light on
  • Possibly hard starting or knocking when cold
  • Further glow plug codes

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 module

Related codes

P037DP037FP0671P0670P052F

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