P0624 Fuel Cap Lamp Control Circuit

P0624 code definition

The P0624 code indicates that there is a problem in the fuel cap lamp control circuit.

What the P0624 code means

The P0624 is an OBD-II generic code that appears when there is something wrong with the fuel cap and it can be identified through various modules, not only the PCM. For example, it can be that the body control module, alternative fuel control module, ABS control module or various other modules have caused the code to be recorded.

What causes the P0624 code?

There are only a few causes for the P0624:

  • Faulty fuel cap
  • Open, shorted or corroded wiring and connections in the controller area network or CAN Bus harness
  • A control module ground strap or wire that has become loose
  • Faulty CAN bus

What are the symptoms of the P0624 code?

There are not many symptoms for the P0624 code, and they will typically include the fuel cap malfunction signal to illuminate, the service engine lamp to light and the code to be stored.

How does a mechanic diagnose the P0624 code?

To assess the P0624 code, the technician uses an OBD-II scanner and considers the data and freeze frame data. They will then clear the fault codes and determine if the code reappears. If so, they do a visual inspection of the wiring to determine if there are any issues, and will then replace or repair components and connections as needed.

They will then retest and if the code persists, they will begin an in-depth electronic diagnosis using a device such as an Autohex or Tech II to identify the area where the electronic malfunction is occurring or where a defective system ground exists.

Common mistakes when diagnosing the P0624 code

A common mistake made when diagnosing the P0624 code is to assume that any stored codes in the freeze frame are the cause of the code in question. This can easily lead you to make unneeded or ineffective repairs. Thorough diagnostics on the CAN Bus are often a wiser approach than operating on scan readings alone.

How serious is the P0624 code?

The P0624 code will not stop a vehicle from operating safely, but it should not be ignored. It is an electrical problem that could be detected through a long list of sensors and modules. Rather than allowing the problem to remain, it is best to take the time to find out where the electrical glitch is occurring.

What repairs can fix the P0624 code?

Fixing the issues that lead to the P0624 code require the following repairs:

  • Validating the code with the scanner and using all of the data to begin addressing the issues that may have caused it to be recorded
  • Clearing the codes and retesting to see if it reappears, and then visually inspecting wiring and connections to repair or replace anything that is in obvious need
  • If these basic steps do not clear the code, it is necessary to consider testing individual control modules
  • The use of a CAN bus tester such as an Autohex or Tech II will identify the area where the problem has occurred, and then it may mean replacing the fuel cap, the control circuits or connections, or the CAN bus itself

Additional comments for consideration regarding the P0624 code

A control module failure is rare, as is a PCM failure. If, however, testing and repairs reveal that there is a need to replace the module, it is of the utmost importance that the testing done identifies the specific module. If it is the PCM it will be necessary to reprogram as well. This is a rarity, though, and the most common issue is typically a faulty fuel cap or a wiring issue that is easily identified and repaired.

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