What Does P037D Mean?
The ECM has detected a fault in the glow plug sense circuit, which is used on diesel engines to monitor the condition and operation of the glow plugs. The sense circuit allows the glow plug control module to verify that each glow plug is actually heating up correctly. The driver may notice hard starting in cold weather, white smoke on cold startup, or a glow plug warning light illuminated on the dashboard.
Common Causes
35%
Failed glow plug with an open or shorted heating element that the sense circuit has detected
25%
Faulty wiring or connector in the glow plug sense circuit
20%
Glow plug control module sense circuit failure
15%
Corroded glow plug bus bar or power distribution connector
5%
ECM communication fault with the glow plug control module
Diagnostic Steps
1
Check glow plug control module data PIDs to identify which specific glow plug(s) the sense circuit is flagging as faulty. Note the current draw or resistance reported for each plug.
2
Measure each glow plug's resistance individually by disconnecting the bus bar and testing from the glow plug terminal to engine ground. A good glow plug typically reads 0.5-2.0 ohms (varies by type). An open circuit (OL) confirms a failed plug.
3
Inspect the sense circuit wiring from the glow plug control module to each glow plug. Look for heat damage, corrosion, or rodent damage on the thin sense wires.
4
Test the glow plug bus bar and power supply connections for excessive resistance. Measure voltage drop from the battery positive terminal to each glow plug terminal during a glow cycle (should be <0.5V drop).
5
Using bidirectional controls, command the glow plug control module to activate each plug individually while monitoring current draw with a clamp-on ammeter. Each plug should draw 15-30A initially, settling to 8-15A (varies by application).
Estimated Repair Cost
$80 - $500
Parts + labor, varies by vehicle and location
The ECM has detected a fault in the glow plug sense circuit, which is used on diesel engines to monitor the condition and operation of the glow plugs. The sense circuit allows the glow plug control module to verify that each glow plug is actually heating up correctly. The driver may notice hard star...
The most common cause of P037D (Glow Plug Sense Circuit) is: Failed glow plug with an open or shorted heating element that the sense circuit has detected
Typical repair costs for P037D range from $80 to $500, depending on the vehicle, location, and whether you do it yourself or go to a shop.
A glow plug sense circuit fault typically does not prevent driving but will cause difficult cold starting and increased cold-start emissions. In very cold weather, the engine may not start at all. The vehicle is safe to drive once started, but repair before cold weather is advisable.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to P037D to identify the root cause.
OBDHut Mobile App
Scan codes directly from your car with the OBDHut app.
Coming Soon
Quick Info
Category
Powertrain
System
Diesel Glow Plug / Cold Start System
Difficulty
Type
Generic (SAE)
Recommended Tools
OBD2 Scanner
A quality scan tool helps you read codes, view live data, and clear faults.
