P0689 Code: Glow Plug Module / Supply Voltage (P0689)
Note: We do not currently have verified model-specific diagnostic data for the Jeep Gladiator. The symptoms and fixes listed below are the standard generic OBD2 guidelines for the P0689 code. Always consult a factory service manual before replacing parts.
What does this mean?
Code P0689 indicates a problem with the glow plug module control circuit or supply voltage (diesel engines).
Diagnostic system: Control module, power, and communication
On a Jeep Gladiator, the P0689 code should be diagnosed as part of the control module, power, and communication group. Related codes and live data from this same system can change the repair priority, so avoid replacing parts from the code name alone.
Most Common Causes for Jeep Gladiator
- Failed glow plug or glow plug module (diesel)
- Damaged, chafed, or broken wiring harness
- Corroded or loose electrical connector
- Internal PCM/ECM failure
- Weak or failing battery
Symptoms to Watch For
- Check Engine Light is illuminated
- Diesel engine hard to start in cold weather
- Glow plug indicator light stays on (diesel)
- White or blue smoke from exhaust
- Rough or unstable idle
Before replacing parts, check these first
- Check battery health, charging voltage, fuses, grounds, and module connectors.
- Look for network communication codes and multiple-module failures.
- Confirm power and ground before suspecting a failed PCM/ECM/TCM.
- Check for blown fuses, weak battery voltage, and damaged connectors before buying major parts.
Live data to compare
- Battery voltage while cranking
- Module power and ground voltage drop
- Network communication codes
How to Diagnose
Common Mistakes
Replacing a control module before checking voltage supply, grounds, fuses, water intrusion, and connector condition. Always confirm the fault with freeze-frame data, live data, visual inspection, and circuit checks before spending money on parts.
Repair verification
After the repair, clear P0689, complete a drive cycle, and confirm the monitor runs without the code returning. Save the before/after scan report if the vehicle needs emissions inspection.
Frequently Asked Questions
Can I drive with the P0689 code?
If the check engine light is solid, you can usually drive to a safe location or mechanic. If the light is flashing, pull over immediately to prevent catastrophic engine or catalytic converter damage.
Will the P0689 code clear itself?
Once the underlying problem is fixed, the engine computer will run its self-checks. If it passes over several drive cycles, the light will turn off automatically. You can also clear it immediately using an OBD2 scanner.
Will this code fail an emissions test?
Yes. If the Check Engine Light is on due to the P0689 code, your Jeep will automatically fail an OBD2 plug-in emissions or smog test.
What should I check first for P0689?
Check battery health, charging voltage, fuses, grounds, and module connectors. Look for network communication codes and multiple-module failures. Confirm power and ground before suspecting a failed PCM/ECM/TCM.
Join the Discussion
Repair Estimate
Fuse, connector, wiring, cleaning, or basic inspection
Control module replacement and programming after power/ground verification
Includes parts and labor. May vary by location.
Power and ground repairs are often cheaper than module replacement, which may also require programming.
DIY Difficulty
Can usually be performed at home with basic hand tools.