What does it mean?
This is a generic diagnostic trouble code (DTC) and applies to many OBD-II vehicles (1996-newer). This may include, but is not limited to, vehicles from Ford, Kia, Chevrolet, GMC, Hyundai, etc. Although generic, the exact repair steps may vary depending on the year, make, model, and powertrain configuration.
A stored P0624 code means that the Powertrain Control Module (PCM) has detected a malfunction in the fuel cap lamp control circuit.
The fuel cap lamp is located on the dashboard. Its main purpose is to warn the driver of a loose or missing fuel cap when it is illuminated.
The operation of the fuel warning lamp is controlled by the PCM. Using input signals from the fuel tank pressure sensor and other sensors, the PCM determines if the fuel cap is properly installed in the fuel filler neck. If the PCM determines that the cap is loose or missing, the fuel cap lamp should be triggered to illuminate.
The PCM typically monitors the continuity of the fuel cap lamp control circuit whenever the engine is running.
Whenever the ignition is turned on and the PCM is powered, several controller self-tests are performed. In addition to running internal controller self-tests, the Controller Area Network (CAN) is used to compare signals from each individual module to ensure that the various controllers interface correctly.
If a problem is detected in the monitoring of the fuel cap lamp control circuit, a P0624 code will be stored and a Malfunction Indicator Lamp (MIL) may illuminate. Depending on the perceived severity of the malfunction, multiple failure cycles may be required for the MIL to light up.
Check the gas cap warning light
P0624 Gas Cap Check Light
How severe is this DTC?
A stored P0624 code should be addressed with some urgency. A loose or missing fuel cap can lead to fuel contamination in addition to allowing harmful fuel vapors to be released into the atmosphere.
What are some of the symptoms of the code?
Symptoms of a P0624 trouble code may include:
- Reduced fuel efficiency
- Deactivation of the evaporative emissions system
- Other stored codes
What are some common causes of the code?
Causes of this code may include:
- Faulty PCM
- PCM programming error
- Open or shorted fuel cap lamp control circuit
- Faulty, loose, or missing fuel cap
- Defective fuel cap warning light bulb
What are the troubleshooting steps for P0624?
A diagnostic scanner, a digital volt/ohmmeter (DVOM), and a reliable source of vehicle information will be needed to diagnose a P0624 code.
Consult your vehicle’s information source for Technical Service Bulletins (TSBs) that match the stored code, the vehicle (year, make, model, and engine), and the symptoms presented. If you find the appropriate TSB, it may provide useful diagnostic information.
Start by connecting the scanner to the vehicle’s diagnostic port and retrieving all stored codes and freeze frame data. You’ll want to note this information, just in case the code proves to be intermittent. After recording all relevant information, clear the codes and test-drive the vehicle until the code resets or the PCM enters readiness mode. If the PCM enters readiness mode, the code is intermittent and will be more difficult to diagnose. The condition that caused the P0624 to be stored may even need to worsen before a diagnosis can be made. If the code resets, continue with your diagnosis.
Use your vehicle information source to obtain connector face views, connector pinout diagrams, component locators, wiring schematics, and diagnostic flowcharts related to the code and the specific vehicle.
If all fuses and relays appear to be functioning as expected, a visual inspection of the wiring and harnesses related to the controller is necessary. You should also check the chassis and engine ground connections. Use your vehicle information source to obtain ground locations for the related circuits. Use the DVOM to test the integrity of the ground.
Visually inspect the system controllers for signs of water, heat, or collision damage. Any damaged controller, especially by water, should be considered faulty.
If the controller’s power and ground circuits are intact, suspect a faulty controller or a controller programming error. Replacing the controller will require reprogramming. In some cases, you can purchase pre-programmed controllers through aftermarket sources. Other vehicles/controllers will require on-board reprogramming that can only be performed by a dealer or another qualified source.
If the fuel tank cap warning light does not illuminate during Key On Engine Off (KOEO) operation, suspect a faulty fuel tank cap warning light bulb.
Test the integrity of the controller ground by connecting the DVOM’s negative test lead to ground and the positive test lead to battery voltage.