Fuel Supply Heater Control Circuit High
The P2689 code indicates that the powertrain control module (PCM) has detected a high voltage condition in the fuel supply heater control circuit. This heater is used to warm diesel fuel in cold temperatures to prevent gelling. A high voltage reading suggests a short to power, a faulty heater relay, or a defective heater element.
01. Most Common Causes
- Short to power in the heater control circuit
- Faulty fuel supply heater relay
- Defective fuel supply heater element
- Corroded or damaged wiring/connectors
02. Symptoms You Will Notice
- Check Engine Light illuminated
- Hard starting in cold weather
- Poor fuel economy
- Engine may run rough or stall
03. Step-by-Step Diagnosis
Step 1: Use a scan tool to retrieve freeze frame data and confirm the code.
Step 2: Visually inspect the fuel heater wiring and connectors for damage or corrosion.
Step 3: Test the fuel heater relay and circuit for shorts to power using a multimeter.
Step 4: Measure resistance of the fuel heater element; compare to manufacturer specs.
Step 5: If all else is normal, replace the fuel heater assembly or relay as needed.
04. Commonly Affected Makes
05. Frequently Asked Questions
Is it safe to drive with this code?▼
It is not recommended to drive with this code, as it can cause hard starting or stalling, especially in cold weather. The high voltage condition may also damage other components.
How much does it cost to fix?▼
Repair costs typically range from $150 to $400, depending on the cause and labor rates. Replacing the fuel heater assembly can be more expensive.