Glow Plug Sense Circuit High Voltage
The P037F code indicates that the glow plug control module has detected a voltage higher than expected on the glow plug sense circuit. This circuit monitors the voltage drop across the glow plugs during the pre-glow and post-glow cycles. A high voltage reading suggests an open circuit, high resistance, or a faulty glow plug control module. This condition can prevent proper glow plug operation, leading to hard starts in cold weather and increased emissions.
1. Most Common Causes
- Faulty glow plug relay or control module
- Open or high resistance in glow plug sense circuit wiring
- Corroded or loose electrical connectors
- Blown fuse for glow plug system
- Failed glow plug(s) causing open circuit
2. Symptoms You Will Notice
- Check Engine Light illuminated
- Hard starting, especially in cold weather
- Excessive white smoke on startup
- Rough idle or misfire during warm-up
- Reduced fuel economy
3. Step-by-Step Diagnosis
Step 1: Scan for additional codes and record freeze frame data.
Step 2: Visually inspect glow plug wiring and connectors for damage, corrosion, or loose connections.
Step 3: Test glow plug resistance using a multimeter; compare to manufacturer specifications.
Step 4: Check glow plug relay and fuse; replace if faulty.
Step 5: If wiring and plugs are good, test glow plug control module output and replace if necessary.
4. Frequently Asked Questions
Is it safe to drive with this code?▼
You can drive, but starting may be difficult in cold weather. Prolonged driving with this code can cause excessive smoke and potential damage to the glow plug system.
How much does it cost to fix?▼
Diagnosis typically costs $50-$150. Repair costs vary: replacing a glow plug relay or fuse is $50-$150, while replacing the glow plug control module can be $200-$500.
5. Commonly Affected Makes
This is a generic OBD2 code, potentially applicable to any manufacturer using this diagnostic standard.