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P2555 OBD-II Trouble Code: Throttle/Fuel Inhibit Circuit High

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P2555 code definition

P2555 is the generic OBD-II code for Throttle/Fuel Inhibit Circuit High.

What the P2555 code means

You will typically see this DTC in diesel-powered vehicles. It indicates that the voltage signal being sent to the PCM (powertrain control module) FICM (fuel injection control module) by the throttle or fuel inhibit circuit falls outside of the expected parameters by more than 10 percent. The FICM regulates how much fuel is delivered by the fuel injectors, and when.

What causes the P2555 code?

The most common causes of this DTC include:

  • Bent or damaged FICM connector pins
  • An open or short in the related circuitry or connectors
  • Defective fuel injectors

What are the symptoms of the P2555 code?

The code will store and the Check Engine or Service Engine Soon lamp will illuminate. There may be engine misfires, or a no-start condition. This DTC is often accompanied by other FICM codes like P2552, P2553, and/or P2554.

How does a mechanic diagnose the P2555 code?

Diagnosis may involve:

  • Using a scanner to read all stored codes and capture freeze frame data
  • Clearing the vehicle’s computer of the fault codes, then test driving the vehicle to see if any of them return
  • Diagnosing and repairing any DTCs which occurred before P2555
  • Visually inspecting all wiring, connectors, and pins associated with the FICM to check for chafing, insulation damage, shorts, opens, loose connections, damaged or bent pins
  • Inspecting the fuel injectors and their wiring and connections, if no connection problems are found with the FICM
  • Testing fuel pump and fuel injection fuses under start-up conditions

Common mistakes when diagnosing the P2555 code

Technicians sometimes turn first to the fuel delivery system, without completely inspecting all of the circuitry and connections involved with the FICM. While the fuel injectors may be at fault, this is much less common than issues with the FICM pins or clips.

How serious is the P2555 code?

This condition can cause the vehicle to exhibit anything from engine misfires to the complete inability to operate the vehicle. This means that it’s important to have the problem addressed as soon as possible, to prevent getting stuck somewhere with a no-start condition as well as to protect the engine from serious damage.

What repairs can fix the P2555 code?

Possible fixes for this DTC include:

  • Repairing any shorts or opens in the FICM wiring and connectors
  • Disconnecting the FICM and closely examining all connections and pins to be sure they’re seated correctly
  • Replacing malfunctioning fuel injectors
  • Replacing the FICM or PCM

Additional comments for consideration regarding the P2555 code

Experts report that the most common source of this DTC setting is by far faulty connections in the FICM. For example, a clip may seem to be seated securely but if it is not all the way connected, pins can back out, triggering this code. Likewise, a bent pin can easily create this issue.

It can be incredibly time consuming and laborious to fix this problem on your own. If a lock tab on the FICM becomes damaged, the clip will no longer be able to hold the FICM connector in place. This is another common source of a P2550 series code setting. If you have recently installed a new FICM, the connections or wiring are almost certain to be the cause of the problem.

In some cases, manufacturers utilize fuel pump safety interrupter switches. You want to make sure this switch has not been activated, otherwise you will waste time carrying out all of the other diagnostic procedures in vain.

Due to the complexity of the wiring and connections involved in the FICM, you will need a manufacturer’s wiring schematic, along with specialized tools such as a scanner and a digital volt/ohmmeter. Don’t hesitate to contact a professional technician if you have trouble with this repair.

Need help with a P2555 code?

YourMechanic offers certified mobile mechanics who will come to your home or office to diagnose and repair your vehicle. Get a quote and book an appointment online or speak to a service advisor at 1-800-701-6230.

The statements expressed above are only for informational purposes and should be independently verified. Please see our terms of service for more details
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