Glow Plug Module Control Circuit Malfunction
The P0670 code indicates a fault in the glow plug module control circuit, which is responsible for controlling the glow plugs during cold starts in diesel engines. The powertrain control module (PCM) monitors the circuit for proper voltage and current. When an open, short, or excessive resistance is detected, this code is set. This can prevent the glow plugs from heating, leading to hard starting in cold weather.
01. Most Common Causes
- Faulty glow plug module
- Open or shorted wiring in the control circuit
- Blown fuse or relay
- Corroded or loose connectors
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: Scan for codes and verify P0670 is present.
Step 2: Inspect the glow plug module fuse and relay; replace if blown.
Step 3: Visually check wiring and connectors for damage, corrosion, or looseness.
Step 4: Test the glow plug module control circuit voltage and ground with a multimeter.
Step 5: If circuit is OK, test the glow plug module itself per manufacturer specs.
04. Commonly Affected Makes
05. Frequently Asked Questions
Is it safe to drive with this code?▼
You can drive, but starting may be difficult in cold weather. Prolonged driving may cause incomplete combustion and increased emissions.
How much does it cost to fix?▼
Diagnosis typically costs $50-$150. Replacing the glow plug module can range from $100 to $400 including parts and labor.