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P2635 – What Does It Mean and How To Fix It

This is one of the most frequent OBD2 trouble codes. Read the full article below to know what it means, how to fix it, and what other codes may show related to it.


P2635 is an OBD-II Code that refers to Fuel Pump A Low Flow/Performance


A P2635 code is a diagnostic trouble code related to that occurs when the PCM/ECM detects a low flow or performance from the fuel pump. The fuel pump works to ensure that the vehicle’s fuel level is correct at all times. The Fuel Pump Control Module in each car calculates the necessary fuel pressure for the engine and informs the PCM accordingly.

If the pressure isn’t within the required parameters, the P2635 code will be set if this module detects it.


Common causes for this code include:

  • Fuel pump is damaged or faulty (possibly owing to damaged brushes, bearings, or armature)
  • Fuel pump relay is damaged or faulty
  • Pump Drive is Damaged or Defective
  • Fuel level is low
  • Damaged or malfunctioning ECM (Rare)


The symptoms of a P2635 code are:

  • Illuminated Check Engine Light
  • The vehicle may refuse to start
  • The car may turn over for some time before actually starting up
  • On acceleration, the car may hesitate


To diagnose a P2635 DTC code, a technician would:

  1. Scan for codes in the ECM and look at the freeze frame data for failure.
  2. Visually inspect the fuel pump and relay for any signs of damage.
  3. Measure the voltage and resistance of the pump drive.
  4. Check the fuel level and inspect the wiring harness for damage.
  5. Confirm that the ECM is functioning properly.

Common mistakes

The following are some of the most common mistakes that a technician may make when diagnosing a P2635 code:

  • Not thoroughly inspecting all the wiring and connectors for damage.
  • Not checking the fuel level.
  • Not checking the pump drive for damage or defectiveness.
  • Not verifying that the ECM is functioning properly.

How serious is this?

A P2635 code is a moderate to serious code and should be fixed as soon as possible. If the fuel pump is not functioning properly, it can lead to a lack of power and even engine failure.

What repairs can fix the code?

The following are solutions that may fix this problem:

  • Repair or replace any wiring that is damaged
  • Replace the fuel pump
  • Replace the fuel pump relay
  • Replace the fuel rail pressure sensor
  • Clean or replace the pump drive
  • Check the ECM for any damage or malfunction (Rare)

Related codes

A P2635 is related to and may be accompanied by the following codes:

P0171 – System too lean

P0271 – Fuel injector 7 control circuit low

P0300 – Random/Multiple Cylinder Misfire Detected


In conclusion, the P2635 code is a diagnostic trouble code that refers to a problem with the fuel pump. There are many potential causes for this code, and the most common ones should be checked first. The code can cause a variety of symptoms, and it is important to fix it as soon as possible to avoid further damage.