Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
Key ON Engine Running (KOER) Glow Plug Monitoring Self-Test
The KOER glow plug monitoring self-test is a functional test of the glow plug system carried out with the ignition ON, engine running and the A/C OFF. Maintain battery voltage at 10.5-14 volts during this test. If necessary, apply the accelerator pedal to increase voltage to the specified level. The PCM activates the glow plug control module (GPCM) and monitors the glow plug circuits. A concern must be present at the time of testing for the test to detect a concern. The DTCs are sent to the PCM and then output to the scan tool.
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.