P2635 OBD-II Trouble Code: Fuel Pump ‘A’ Low Flow / Performance

P2635 Code Definition

A P2635 code is a generic powertrain code related to computer output circuit issues. It means that the fuel pump 'A’ is registering a low flow, or one not within the preset parameters.

Codes related to a P2635 include:

• P0627: Fuel Pump A Control Circuit/Open
• P0628: Fuel Pump A Control Circuit Low
• P0629: Fuel Pump A Control Circuit High
• P2632: Fuel Pump B Control Circuit /Open
• P2633: Fuel Pump B Control Circuit Low
• P2634: Fuel Pump B Control Circuit High
• P2636: Fuel Pump B Low Flow / Performance

What the P2635 Code Means

The fuel pump uses a connector at the top of the fuel tank to supply power as well as ground to the fuel pump. It also provides power to the sensing wires for the fuel level sender. The fuel level sender communicates fuel level by a float that sits on top of the fuel level. An electric motor moves the gas through and pressurizes the fuel system.

A P2635 code will appear when the engine control module (ECM) detects low fuel flow or low fuel pressure in fuel pump A.

What Causes the P2635 Code?

There are several possible causes of a P2635 code including:

• Damaged or defective fuel pump (possibly due to damaged brushes, bearings or armature)

• Damaged or defective fuel pump relay

• Damaged or defective fuel pump driver

• Lack of fuel

• Damaged or defective ECM (rare)

What are the Symptoms of the P2635 Code?

Symptoms of a P2635 code can include:

• Warning or Check Engine Light may illuminate
• The vehicle may not start at all
• The vehicle may crank over for an extended period of time before actually starting up
• The vehicle may hesitate on acceleration

How Does a Mechanic Diagnose the P2635 Code?

A mechanic may use several methods to diagnose a P2635 code including:

• Using an OBD-II scanner to check for a stored P2635 code
• Visually inspecting all wiring and electrical components for possible damage
• Using a fuel pressure gauge to test the fuel pressure if the vehicle will not start
• Checking if the electric fuel pump is operating (can be done by listening)
• Testing the fuel pump for proper or intermittent operation
• Checking the fuel pump for sediment build up
• Checking battery voltage at the fuel pump connector
• Checking fuel rail pressure sensor voltage
• Clearing all codes, test driving the vehicle, and rescanning it to see if any codes reappear

Common Mistakes when Diagnosing the P2635 Code

There have been reports of vehicles simply being out of fuel or having a damaged or defective fuel gauge and being diagnosed with a P2635 code. Ensure the vehicle has fuel before proceeding with additional diagnosis and repairs.

How Serious is the P2635 Code?

Because a vehicle may not start or may hesitate during acceleration, this can cause potentially dangerous driving conditions. For this reason, this is considered a serious code and it is recommended to have it diagnosed and repaired as soon as possible.

What Repairs can Fix the P2635 Code?

• Repairing or replacing any damaged or defective wiring and electrical components
• Repairing or replacing a damaged or defective fuel pump
• Repairing or replacing a damaged or defective fuel rail pressure sensor
• Repairing or replacing a damaged or defective fuel pump relay
• Repairing or replacing a damaged or defective fuel pump drive
• Repairing or replacing a damaged or defective ECM (rare)

Need Help with a P2635 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.