Glow Plug Sense Circuit Low Voltage
The P037E code indicates that the glow plug control module has detected a low voltage condition 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 low voltage reading suggests excessive resistance or an open circuit in the glow plug wiring, a faulty glow plug, or a failing glow plug control module. This issue primarily affects diesel engines, leading to hard starting in cold weather and increased emissions.
1. Most Common Causes
- Open or high-resistance glow plug
- Sense circuit wiring shorted to ground
- Corroded or damaged connector/terminal in glow plug harness
- Faulty glow plug control module (GPCM)
- Altered sense circuit shunt resistor
- Internal ECM failure in the sense circuit detection stage
2. Symptoms You Will Notice
- Hard starting, especially in cold weather
- Check Engine Light illuminated
- Excessive white smoke on startup
- Rough idle or misfire during warm-up
3. Step-by-Step Diagnosis
Step 1: Scan for codes and record freeze frame data.
Step 2: Visually inspect glow plug wiring and connectors for damage or corrosion.
Step 3: Measure resistance of each glow plug; typical spec is 0.5-2.0 ohms.
Step 4: Check voltage at glow plug control module output; should be battery voltage during glow cycle.
Step 5: Test glow plug control module per manufacturer procedure.
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 can cause incomplete combustion and damage the catalytic converter.
How much does it cost to fix?▼
Typically $50-$150 for parts and labor, depending on the cause. Glow plugs cost $10-$30 each, and labor is 1-2 hours.
5. Commonly Affected Makes
This is a generic OBD2 code, potentially applicable to any manufacturer using this diagnostic standard.