Damaged or corroded glow plug sense circuit wiring, including chafed insulation or broken strands; Failed glow plug with an open or shorted sensing element; Poor electrical connection at the glow plug, harness connector, or ground point; Faulty glow plug control module (GPCM) or relay not providing correct feedback voltage; Corrosion or water intrusion in the sense circuit connector causing high resistance; PCM internal fault on the sense circuit input, though this is less common

DTC codes / P03xx · Ignition system and misfire / P037E

P037EGlow Plug Sense Circuit Low

Q: What does code P037E mean?

Glow Plug Sense Circuit Low. P037E indicates that the powertrain control module (PCM) has detected a low-voltage condition on the glow plug sense circuit, which is the feedback line used to monitor glow plug operation. The PCM expects a specific voltage range on this circuit when the glow plugs are commanded on or off, and a reading below the threshold triggers this code.

P037E indicates that the powertrain control module (PCM) has detected a low-voltage condition on the glow plug sense circuit, which is the feedback line used to monitor glow plug operation. The PCM expects a specific voltage range on this circuit when the glow plugs are commanded on or off, and a reading below the threshold triggers this code.

SystemPowertrain

Code typeGeneric (all makes)

SeverityMedium

Fix difficultyIntermediate

AreaIgnition system and misfire

Symptoms you may notice

Illumination of the check engine light or glow plug warning lamp
Hard cold starting or extended cranking before the engine fires
Rough idle and white smoke immediately after a cold start
Reduced engine performance and poor fuel economy during warm-up
Often no symptoms besides the warning light, especially in mild weather

Common causes, most likely first

Damaged or corroded glow plug sense circuit wiring, including chafed insulation or broken strands
Failed glow plug with an open or shorted sensing element
Poor electrical connection at the glow plug, harness connector, or ground point
Faulty glow plug control module (GPCM) or relay not providing correct feedback voltage
Corrosion or water intrusion in the sense circuit connector causing high resistance
PCM internal fault on the sense circuit input, though this is less common

How to diagnose and fix it

Inspect the glow plug sense circuit wiring and connectors for damage, corrosion, or loose pins, and repair as needed
Measure resistance of each glow plug and compare to the manufacturer's specification to identify a failed plug
Check the glow plug control module or relay for proper operation and replace if faulty
Perform a voltage drop test on the sense circuit to locate excessive resistance under load
Verify the sense circuit voltage at the PCM connector matches expected values during glow plug activation
Repair or replace any damaged sections of the sense circuit harness
Clear the code and perform a cold-start drive cycle to confirm the repair

Sense Circuit Faults Often Misdiagnosed

A low sense circuit voltage does not always mean the glow plug itself has failed; the sense line is a separate feedback wire that can corrode or break independently of the power circuit.
Technicians often replace glow plugs unnecessarily when the real problem is a chafed sense wire near the engine block or a corroded connector pin that only acts up in cold, damp conditions.
The glow plug control module can set this code if its internal feedback circuit fails, even when all glow plugs test good, so module testing should follow wiring and plug checks.
On some vehicles, a weak battery or poor chassis ground can cause a low voltage condition on the sense circuit during cranking, mimicking a failed component.
After repairs, the PCM may need a relearn or several cold-start cycles before the code clears permanently, so do not assume the fix failed if the light stays on briefly.

Can I keep driving with P037E?

You can usually drive the vehicle, but cold starting may be difficult and prolonged driving with a faulty glow plug system can lead to excessive white smoke and engine wear. Avoid heavy loads and long idling until the fault is repaired, and address it promptly to prevent secondary damage.

Tools that help

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Guidance is general and written for all OBD-II vehicles. Exact tests and values vary by model, so confirm the fault before replacing parts.