What it means
The control circuit for the fuel cap warning lamp reports a fault. The ECM cannot drive the indicator that warns of an open or loose fuel cap.
At a glance
- Usually lights the check-engine light
How it works
The fuel-cap lamp control circuit lets the ECM operate the dashboard indicator that warns when the fuel cap is open or loose. P0624 is set when the ECM detects a fault in that indicator-control circuit, so the warning may not appear when needed or may behave unexpectedly.
Common causes
Most likely first.
- Lamp circuit open or shorted
- Instrument cluster fault
Symptoms
- Fuel-cap warning lamp may not operate correctly
How to diagnose it
- Record freeze-frame data and check for other fuel-cap or evaporative-system codes that could explain why the warning was requested.
- Check whether the fuel-cap warning indicator illuminates during the normal dashboard bulb check and whether it responds when the warning is commanded, if scan-tool controls are available.
- Inspect the indicator wiring and connectors between the ECM and instrument cluster for damage, corrosion, or loose pins.
- Check the instrument-cluster ground and the lamp or display element for an open circuit.
- Test the control wire for continuity and shorts, then verify the ECM output and cluster response against the manufacturer's specification.
Common fixes
- Secure or clean a loose, contaminated cluster or ECM connector.
- Repair an open or shorted fuel-cap lamp control wire.
- Repair the failed warning lamp or instrument-cluster circuit.
- Replace or repair the ECM control output only if circuit testing confirms an internal fault.
Can I keep driving?
The vehicle will usually remain drivable, but you may not receive the fuel-cap warning if the cap is loose. Check that the cap is tightened after refuelling and have the indicator circuit repaired.
A code shows where the control module detected a fault, not always which part failed. Check the causes in order and confirm with a test before replacing parts. Have several codes? Check them together
This is a generic code: it means the same on every make. The car’s maker may add more detail in its own service information.