What it means
Glow plug sense line above upper plausibility — open signal or short to B+. Wiring faults of this kind typically come from chafing, water ingress at connector seals, or pin push-back — a wiggle test on the harness while the code is active often confirms the location.
At a glance
- Usually lights the check-engine light
- Affects emissions; the car can fail an emissions test
How it works
The glow plug sense circuit returns current-related feedback to the control module. P037F sets when that feedback rises above its expected range, which can result from an open signal wire or a short to battery voltage.
Common causes
Most likely first.
- Open signal line
- Connector pins corroded - high contact resistance
- Supply wire pinched against B+ source
Symptoms
- Glow plug warning light on (often orange coil symbol)
- Hard cold start or no start in cold weather
- White smoke from exhaust during warm-up
How to diagnose it
- Record freeze-frame data and compare commanded glow plug operation with the sense feedback at the time the code set.
- Inspect the sense-circuit harness and connectors for a broken wire, chafing against a power feed, corrosion, or pushed-back pins.
- Check whether the glow plug lamp and cold-start symptoms are consistent with missing or unreliable current feedback.
- With the circuit isolated as directed by the manufacturer, test for an open signal path and a short to battery voltage.
- If the harness passes, test the sensing module and control unit against the manufacturer's specification.
Common fixes
- Repair an open or broken sense-circuit wire.
- Repair wiring shorted to a power feed.
- Clean or repair corroded, loose, or pushed-back connector terminals.
- Replace the sensing module or control unit if testing identifies it as faulty.
Can I keep driving?
Glow plug operation may not be properly verified, and cold starts can be difficult with white smoke during warm-up. Avoid repeated prolonged cranking in cold conditions.
A code shows where the control module detected a fault, not always which part failed. Check the causes in order and confirm with a test before replacing parts. Have several codes? Check them together
This is a generic code: it means the same on every make. The car’s maker may add more detail in its own service information.