Cylinder 4 Glow Plug Control Circuit Low
The P067A code indicates that the powertrain control module (PCM) has detected a low voltage condition in the glow plug control circuit for cylinder 4. This typically means the glow plug or its wiring has excessive resistance or a short to ground, preventing proper heating for cold starts. In diesel engines, glow plugs preheat the combustion chamber; a fault can cause hard starting, misfires, and increased emissions.
01. Most Common Causes
- Faulty glow plug in cylinder 4
- Open or shorted wiring in the glow plug circuit
- Corroded or loose connector at the glow plug
- Failed glow plug control module or relay
02. Symptoms You Will Notice
- Hard starting, especially in cold weather
- Engine misfire or rough idle on cold start
- Check Engine Light illuminated
- Reduced fuel economy
03. Step-by-Step Diagnosis
Step 1: Scan for codes and record freeze frame data.
Step 2: Visually inspect the glow plug wiring and connector for cylinder 4 for damage or corrosion.
Step 3: Measure resistance of glow plug 4; compare to spec (typically 0.5-2 ohms).
Step 4: Check voltage at the glow plug connector with key on; should be battery voltage.
Step 5: Test the glow plug control module output for cylinder 4.
04. Commonly Affected Makes
05. Frequently Asked Questions
Is it safe to drive with this code?▼
You can drive short distances in mild weather, but cold starts will be difficult and may cause engine damage if the cylinder misfires repeatedly. It's best to repair promptly.
How much does it cost to fix?▼
Typically $50-$150 for a single glow plug replacement, including parts and labor. If the control module or wiring is faulty, costs can be higher.