P2635 GMC Code - Fuel Pump Flow Performance
Quick Answer
The Engine Control Module (ECM) supplies voltage to the fuel pump driver control module when the ECM detects that the ignition is on. Common causes include Faulty Fuel Pump, Fuel Pump harness is open or shorted, Fuel Pump circuit poor electrical connection. Severity is High - diagnose this code as soon as possible. Driving is not recommended if the warning light is flashing, the engine runs poorly, or safety-related symptoms are present.
- What it means
- P2635 GMC indicates Fuel Pump Flow Performance.
- Common causes
- Common causes include Faulty Fuel Pump, Fuel Pump harness is open or shorted, Fuel Pump circuit poor electrical connection.
- Severity
- High - diagnose this code as soon as possible.
- Can I drive?
- Driving is not recommended if the warning light is flashing, the engine runs poorly, or safety-related symptoms are present.
Code P2635 GMC Description
The Diagnostic Trouble Code (DTC) will be set when the fuel pump driver control module detects a difference of ± 60 kPa (8.7 PSI) at 400 kPa (58 PSI) request or ±45 kPa (6.5 PSI) at 300 kPa (43.5 PSI) request between the desired fuel pressure and the actual fuel pressure for approximately 10 s.
What are the Possible Causes of the DTC P2635 GMC?
- Faulty Fuel Pump
- Fuel Pump harness is open or shorted
- Fuel Pump circuit poor electrical connection
- Faulty Fuel Pump Control Module (if applicable)
How to Fix the DTC P2635 GMC?
Review the 'Possible Causes' above and visually examine the corresponding wiring harness and connectors. Check for damaged components and inspect connector pins for signs of being broken, bent, pushed out, or corroded.
Code Tech Notes
- 2014-2018 GMC Sierra
- 2015-2018 GMC Yukon
- 2015-2018 GMC Yukon XL
If the Diagnostic Trouble Codes (DTC) P2635, U0074, and/or U18A2 are set, it may be found that the actual fuel pressure (low-pressure system) will be reading substantially higher than desired fuel pressure, in this case, the cause of the problem is a loss of communication between Engine Control Module (ECM) and Fuel Pump Control Module (FPCM).
- Diagnose for any communication DTCs set (U0074 would take priority over U18A2 if both set) before addressing DTC P2635.
- If DTC P2635 is not resolved by correcting the communication DTCs, only then should diagnose the DTC P2635.
- It has been found that a communication issue between the FPCM and ECM can potentially induce DTC P2635 and result in a pressure differential between actual and desired fuel system pressures.
- If the actual fuel pressure is substantially higher than desired (10 psi / 70 kPa or more), replacement of the fuel pump control module or fuel system components typically will not resolve this issue.
- If the actual fuel pressure is substantially lower than desired (10 psi / 70 kPa or more), this Factory Service Bulletin would NOT apply. It would be recommended to diagnose low actual fuel pressure.
What is the Cost to Diagnose the Code?
Labor: 1.0
To diagnose the P2635 GMC code, it typically requires 1.0 hour of labor. Rates vary by location, vehicle, and shop. Many shops charge between $80–$150 per hour; dealerships and metro areas may be higher, independents may be lower.
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Information for Specific GMC Models
- P2635 2014 GMC Sierra — Fuel Pump Flow Performance
- P2635 2015 GMC Sierra — Fuel Pump Flow Performance
- P2635 2016 GMC Sierra — Fuel Pump Flow Performance
- P2635 2017 GMC Sierra — Fuel Pump Flow Performance
- P2635 2018 GMC Sierra — Fuel Pump Flow Performance
Frequently Asked Questions about P2635 GMC Code
1. What are the common symptoms of OBDII code P2635 GMC (Fuel Pump Flow Performance)?
The common symptoms include rough idling, decreased fuel efficiency, engine misfires, and difficulty starting the vehicle.
2. What are the possible causes of OBDII code P2635 GMC?
The code P2635 GMC can be caused by a faulty fuel pump, clogged fuel filter, fuel pressure regulator issues, or wiring/connectivity problems in the fuel pump circuit.
3. How can I diagnose the OBDII code P2635 GMC?
Diagnosing the code involves checking the fuel pump operation, fuel pressure levels, fuel filter condition, and inspecting the wiring and connectors related to the fuel pump circuit.
4. Can a clogged fuel filter trigger the OBDII code P2635 GMC?
Yes, a clogged fuel filter can restrict fuel flow to the engine, leading to inadequate fuel pump flow performance and triggering the OBDII code P2635 GMC.
5. What are some repair tips for addressing OBDII code P2635 GMC?
Repair tips include replacing a faulty fuel pump, cleaning or replacing a clogged fuel filter, checking the fuel pressure regulator, and ensuring proper wiring connections.
6. Can OBDII code P2635 GMC lead to other issues if left unaddressed?
Yes, leaving the code unresolved can lead to poor engine performance, potential engine damage, and further fuel system issues over time.
7. Is it safe to continue driving with OBDII code P2635 GMC illuminated?
It is not recommended to continue driving with the code illuminated, as it can impact vehicle performance and potentially cause further damage to the fuel system.
8. How much does it typically cost to repair OBDII code P2635 GMC?
The cost of repairing the code can vary depending on the specific issue causing it, but it may range from $200 to $800, including parts and labor.
9. Can I reset the OBDII code P2635 GMC without fixing the underlying issue?
Resetting the code without addressing the underlying problem will only temporarily clear the code, and it is likely to reappear once the issue persists.
10. Is it possible to prevent OBDII code P2635 GMC from occurring?
Regular maintenance, such as fuel system inspections, timely fuel filter replacements, and addressing fuel pump issues promptly, can help prevent the occurrence of the code.
Discuss the causes and fixes for P2635 GMC OBDII Code
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2016 Yukon XL 5.3L
Threw this code (P2635) and has a rough idle. I'll try to update as I find out more information.
If you have any info that would be great too.
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There is a Factory Service Bulletin for that problem, the factory recommend using octane levels greater than 91. If the problem persist, you may have to replace the Fuel Pump.
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Great question. The P2635 code on a GMC usually refers to a problem with the low-pressure side of the fuel system—specifically the fuel pump in the tank not delivering enough volume or pressure to the high-pressure system.
This code often triggers when:
- The in-tank pump (low-pressure) is weak or failing
- There’s a restriction in the fuel line or filter
- The fuel pump control module (FPCM) isn’t commanding proper pump operation
- Or there's an electrical issue like poor ground or low voltage to the pump
The high-pressure fuel pump (on the engine) can still function, but if the low-pressure supply is inconsistent, it can cause hesitation, hard starts, or limp mode.
So yes—P2635 is typically a low-pressure system issue, not the high-pressure pump. A fuel pressure test (both low and high sides if possible) will usually confirm where the issue is. Let me know the engine and model year and I can guide you on expected pressure specs.
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