Technical Description of OBD-II Trouble Code
The circuit that controls the fuel cap lamp
What does that mean?
This is a generic diagnostic trouble code (DTC) that is applicable to many OBD-II vehicles (1996-newer). This includes vehicles from Ford, Kia, Chevrolet, GMC, Hyundai, and others. Although it is a generic code, the specific repair steps may vary depending on the year, make, model, and powertrain configuration of the vehicle.
A stored code P0624 indicates that the powertrain control module (PCM) has detected a malfunction in the fuel cap lamp control circuit.
The fuel cap lamp is located in the instrument panel and its main purpose is to alert the driver when the fuel cap is loose or missing by illuminating.
The PCM controls the operation of the fuel warning lamp. By using input signals from the fuel tank pressure switch and other sensors, the PCM determines whether the fuel cap is properly installed in the fuel filler neck. If the PCM determines that the cap is loose or missing, it should trigger the illumination of the fuel cap lamp.
Whenever the engine is running, the PCM typically monitors the continuity of the fuel cap lamp control circuit.
Each time the ignition is turned on and the PCM is powered, multiple self-tests are performed by the controller. In addition to running internal self-tests, the controller area network (CAN) is used to compare signals from each individual module to ensure proper interfacing of the various controllers.
If a problem is detected in monitoring the fuel cap lamp control circuit, a code P0624 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 MIL illumination.
Check gas cap warning light:
What is the severity of this DTC?
A stored code P0624 should be addressed with some urgency. A loose or missing fuel cap may result in fuel contamination and the release of harmful fuel vapors into the atmosphere.
What are some of the symptoms of the code?
Symptoms of a P0624 trouble code may include:
What are some of the common causes of the code?
Possible causes for this code may include:
What are some P0624 troubleshooting steps?
To diagnose a code P0624, you will need a diagnostic scanner, a digital volt/ohmmeter (DVOM), and a reliable source of vehicle information.
Refer to your vehicle information source for any technical service bulletins (TSB) that match the stored code, vehicle details (year, make, model, and engine), and exhibited symptoms. If you find a relevant TSB, it may provide helpful diagnostic information.
Start by connecting the scanner to the vehicle diagnostic port and retrieving all stored codes and freeze frame data. It is important to write down this information in case the code is intermittent. After recording the necessary information, clear the codes and test drive the vehicle until the code is reset or the PCM enters readiness mode. If the PCM enters readiness mode, the code is intermittent and will be more challenging to diagnose. In some cases, the condition that caused the P0624 to be stored may need to worsen before a diagnosis can be made. If the code is reset, continue with the diagnosis.
Use your source of vehicle information to obtain connector face views, connector pin-out charts, component locators, wiring diagrams, and diagnostic flow charts related to the code and the specific vehicle.
If all fuses and relays appear to be functioning correctly, visually inspect the wiring and harnesses related to the controller. Also, check the chassis and engine ground junctions. Use your vehicle information source to find the ground locations for the relevant circuits. Use the DVOM to test the integrity of the grounds.
Inspect the system controllers for any signs of water, heat, or collision damage. Any damaged controller, especially if water damage is present, should be considered defective.
If the power and ground circuits of the controller are intact, suspect a defective controller or a controller programming error. Controller replacement will require reprogramming. In some cases, reprogrammed controllers may be available through aftermarket sources. Other vehicles/controllers may require on-board reprogramming, which can only be done by a dealership or another qualified source.
