P0624 Fuel Cap Lamp Control Circuit

Description and meaning of DTC p0624

This is a generic diagnostic trouble code (DTC) and applies to many OBD-II vehicles (1996-newer). That 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 year, make, model and powertrain configuration. A stored code P0624 means that the powertrain control module (PCM) has detected a malfunction with the fuel cap lamp control circuit. The fuel cap lamp is contained in the instrument panel. Its primary purpose is to warn the driver of a loose or missing fuel cap, when it is illuminated. Fuel warning lamp operation is controlled by the PCM. Using input signals from the fuel tank pressure switch and other sensors, the PCM determines whether or not the fuel cap is properly installed in the fuel filler neck. If the PCM determines that the cap is loose or missing, fuel cap lamp illumination should be triggered. The PCM typically monitors the continuity of the fuel cap lamp control circuit whenever the engine is running. Each time the ignition is turned on and the PCM is energized, multiple 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 are interfacing properly. 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 be illuminated. Depending upon the perceived severity of the malfunction, multiple failure cycles may be necessary for MIL illumination.

p0624 diagnostic trouble code symptoms

Symptoms of a P0624 trouble code may include:Diminished fuel efficiencyEvaporative emissions system deactivationOther stored codes

DTC p0624 - possible causes

Causes for this code may include:Faulty PCMPCM programming errorOpen or shorted fuel cap lamp control circuitDefective, loose, or missing fuel capFailed fuel cap warning lamp bulb

How to fix OBD-II diagnostic trouble code p0624

A diagnostic scanner, a digital volt/ohmmeter (DVOM), and a source of reliable vehicle information will be required to diagnose a code P0624. Consult your vehicle information source for technical service bulletins (TSB) that replicate the code stored, vehicle (year, make, model, and engine), and symptoms exhibited. If you find the appropriate TSB, it may yield helpful diagnostic. Begin by connecting the scanner to the vehicle diagnostic port and retrieving all stored codes and freeze frame data. You will want to write this information down, just in case the code proves to be an intermittent one. After recording all pertinent 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 difficult to diagnose. The condition, which caused the P0624 to be stored, may even need to worsen before a diagnosis can be made. If the code is reset, continue with your 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 vehicle in question. If all fuses and relays appear to be functioning as intended, a visual inspection of controller related wiring and harnesses is in order. You will also want to check chassis and engine ground junctions. Use your vehicle information source to obtain ground locations for related circuits. Use the DVOM to test ground integrity. Visually inspect system controllers for signs of water, heat, or collision damage. Any controller that is damaged, especially by water, should be considered defective. If controller power and ground circuits are intact, suspect a defective controller or a controller programming error. Controller replacement will require reprogramming. In some cases, you may purchase reprogrammed controllers through aftermarket sources. Other vehicles/controllers will require on-board reprogramming that may only be done through a dealership or other qualified source. If the fuel cap warning lamp fails to illuminate during key-on-engine-off (KOEO) operation, suspect a defective fuel cap warning lamp bulbTest controller ground integrity by connecting the negative test lead of the DVOM to ground and the positive test lead to battery voltage

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