P2636: A second fuel pump (pump B) is not delivering enough fuel
Fuel pump B low flow / performance
Severity: Inspect soon
GM's recall on this code says that if it is not fixed the front tank can run dry and the truck can stall, so a low-flow fuel pump should be checked soon.
P2636 in short
P2636 means the computer found fuel pump B is not moving enough fuel. On 2015-2016 GM diesel trucks with two tanks it is the pump that moves fuel from the rear tank to the front one, and GM warns the truck can run out of fuel and stall. A blocked filter or failing pump are the usual causes.
Some vehicles have a second fuel pump, called pump B. The computer watches how well it moves fuel and sets P2636 when the flow or performance falls short of the target.
On 2015-2016 GM 6.6L LML diesel trucks with two fuel tanks, GM's recall 17067 says pump B is the transfer pump that moves fuel from the rear tank to the front. When the transfer is too slow the code sets, the fuel gauge shows empty and the transfer pump is disabled until it is serviced. The truck can then run out of fuel in the front tank and stall. GM's fix changes the fuel line connections and reprograms the computer.
TroubleCodes.net gives the likely causes in general as a blocked fuel filter or the fuel pump. Two 2015-2016 Silverado 3500 owners report P2636 with a failed transfer pump and a stall. An Acura NSX owner reports the same code with P0087.
Most likely causes
Cause 1: Rear-to-front fuel transfer pump unable to keep up (2015-2016 GM 6.6L diesel, dual tanks)
Supported by vehicle data- Why it ranks here
- GM recall 17067 names P2636 for this fault and changes the plumbing to fix it. Two Silverado 3500 owners report the code with a failed transfer pump. The summary comes from the NHTSA flat file, so status stays unverified.
- What would change this
- Rises on a dual-tank 2015-2016 Duramax if a dealer finds the recall open or the transfer pump failed. Falls on any other vehicle.
Cause 2: Fuel pump B worn or failing
Common general cause- Why it ranks here
- TroubleCodes.net lists the fuel pump itself as a likely cause of a low-flow code, and the Silverado and NSX complaints both describe a failed pump.
- What would change this
- Rises if a fuel pressure and flow test falls short. Falls if pressure and flow meet specification.
Cause 3: Blocked fuel filter
Common general cause- Why it ranks here
- TroubleCodes.net lists a blocked fuel filter first among the probable causes.
- What would change this
- Rises if the filter is overdue or clogged and flow improves with a new one. Falls if the filter is clean.
What to test first
Start at step 1. Each result tells you what it means and where to go next.
Step 1: Read all stored codes and freeze-frame data. Note P0087 or other fuel pressure codes stored with P2636.
IfThe vehicle is a 2015-2016 dual-tank GM 6.6L diesel
It meansAsk a dealer about recall 17067.
IfAnother vehicle
It meansHave the fuel supply tested.
Step 2: Ask a Chevrolet or GMC dealer whether recall 17067 applies and has been done on your VIN.
IfThe recall is open
It meansHave it completed; it changes the fuel line connections and reprograms the computer.
Points to: Rear-to-front fuel transfer pump unable to keep up (2015-2016 GM 6.6L diesel, dual tanks)
IfThe recall is done or does not apply
It meansHave the pump and filter tested.
Step 3: Have a shop check the fuel filter and test fuel pump pressure and flow against the vehicle specification.
Warning:The fuel system stays pressurized after the engine is off and fuel can leak or ignite. Pressure relief and fuel line work belong in a shop.
IfThe filter is clogged
It meansReplace it and retest.
IfPressure or flow falls short with a good filter
It meansThe pump is weak.
Symptoms
- Check engine light
- Fuel gauge reads empty or swings between full and empty
- Engine stalls or will not restart Gets more serious: stop and have it checked.
- Fuel smell Gets more serious: stop and have it checked.
How to fix
Parts and cost context
- Fuel pump:On 2015-2016 dual-tank GM diesels the fix in the recall is new fuel line connections and a software update, not just the pump. Labour varies; get a quote.
Labor varies by vehicle and shop; get a quote before you approve a repair.
Compare used part prices on PartPriceGuideOn your vehicle
ChevroletYour car
2015–2016 · Silverado 3500 HD
Supported by vehicle dataTwo owners report P2636 with a transfer pump failure on dual-tank Duramax trucks, and GM's recall covers this fuel system on Silverado 2500 trucks.
2015–2016 · Silverado 2500 HD
Supported by vehicle dataCovered by GM recall 17067 for dual-tank 6.6L LML diesels.
17067 (chevrolet)Status unverified
Product emissions recall: 6.6L LML diesel with dual fuel tanks, P2636
2015–2016silverado-2500-hd · issued · NHTSA 10143408
Replace the fuel line connections so both tanks can feed the engine, and reprogram the engine computer for the new connection.
We couldn't confirm whether this bulletin is still current, so it doesn't count as confirmation.
GMCYour car
2015–2016 · Sierra 3500 HD
Supported by vehicle dataCovered by GM recall 17067 for dual-tank 6.6L LML diesels.
17067 (gmc)Status unverified
Product emissions recall: 6.6L LML diesel with dual fuel tanks, P2636
2015–2016sierra-3500-hd · issued · NHTSA 10143408
Replace the fuel line connections so both tanks can feed the engine, and reprogram the engine computer for the new connection.
We couldn't confirm whether this bulletin is still current, so it doesn't count as confirmation.
AcuraYour car
2017 · NSX
Possible — needs testingOne owner reports P0087 and P2636 for a fuel pump failure and asks to be added to a recall; only the owner's statement was read, not the recall.
Related codes
Sources and review
- GM 17067: product emissions recall, 6.6L LML diesel with dual fuel tanks, P2636
- P2636 trouble code page
- NHTSA complaint ODI 10966548
- NHTSA complaint ODI 10966553
- NHTSA complaint ODI 11673469
- Last reviewed
- Written by
- Saurabh K.
- Editorial review
- Pending
- Technician review
- Technician review pending
This page explains what a code usually means; it is not a substitute for a professional inspection. How we source and review · Report an error