Glow Plug Sense Circuit High
The P037F code indicates that the powertrain control module (PCM) has detected a voltage signal from the glow plug sense circuit that is higher than the expected range. This circuit monitors the resistance and current flow of the glow plugs during the pre-glow and post-glow cycles. A high voltage reading typically points to an open circuit, a faulty glow plug, or a wiring issue, which can prevent proper cylinder heating and cause hard starting in cold conditions.
01. Most Common Causes
- Open or shorted glow plug
- Damaged wiring or connector in the glow plug sense circuit
- Faulty glow plug control module
- Corrosion or poor electrical connection
02. Symptoms You Will Notice
- Hard starting, especially in cold weather
- Check Engine Light illuminated
- Excessive white smoke on startup
- Rough idle or misfire until engine warms up
03. Step-by-Step Diagnosis
Step 1: Use a scan tool to retrieve all stored codes and freeze frame data.
Step 2: Visually inspect glow plugs and wiring for damage, corrosion, or loose connections.
Step 3: Measure resistance of each glow plug with a multimeter; compare to manufacturer specs (typically 0.5-2 ohms).
Step 4: Check voltage at the glow plug connector with key on; should be battery voltage. If not, test the glow plug relay and control module.
04. Commonly Affected Makes
05. Frequently Asked Questions
Is it safe to drive with this code?▼
It is not recommended to drive long distances, especially in cold weather, as the engine may be hard to start and could run poorly, potentially causing further damage.
How much does it cost to fix?▼
The cost typically ranges from $50 to $150 for parts and labor, depending on whether you need to replace a glow plug or repair wiring.