P2633: Fuel Pump B Control Circuit Low

P2633 is the ground-short code of the second fuel pump circuit. GM's 2014 LML diesel table checks the ground-switched relay output of the fuel transfer pump while it is off and flags 0.5 ohm or less between signal and ground, held for 3 s, as Type B. The 2020 diesel table 20OBDG04 looks at the supply-side switch of the rear-tank transfer pump while it is on and stores a Type C code, without warning lamp, after 20 failures in 25 samples of 250 ms. VW's 2014 data books for Golf, GTI and Beetle set P2633 for the auxiliary in-line pump once the signal voltage stays under 2.0 V. GM bulletin PIT5212B groups it with P2632, P2634 and P2636 on 2013 dual-tank chassis cabs. A grounded wire usually blows a fuse or stops the pump.

Symptoms

• Blown fuse, second pump does not run
• Fuel not transferred from the auxiliary tank
• Warning lamp depending on manufacturer

Most likely causes

• Chafed pump wire grounded against frame or tank strap
• Shorted pump motor windings
• Water in the connector under the vehicle

What to check, in order

Start with the simplest. You can tick off each step.

1. Check the pump's fuse, relay, and connector
2. With the connector unplugged, check whether the signal wire is making contact with ground.
3. Replace the filter if it is due for maintenance
4. Compare commanded and actual pressure in live data
5. Measure the pressure with a suitable gauge
6. Check the sensor and regulator before replacing the pump

Good to know

• Repair difficulty: medium
• It affects emissions.

What each character of P2633 means

• P: Powertrain: engine and transmission
• 2: Generic code: same on every make
• 6: Control modules and outputs
• 33: Specific fault in that system

Frequently asked questions

Can I keep driving with code P2633?

Avoid long trips and hard acceleration. If you smell fuel or the car stalls, do not continue.

What causes code P2633?

The most common causes are: chafed pump wire grounded against frame or tank strap; shorted pump motor windings; water in the connector under the vehicle.

Related codes

• P2632Fuel Pump B Control Circuit/Open
• P2634Fuel Pump B Control Circuit High
• P2636Fuel Pump B Low Flow/Performance
• P0628Fuel Pump A Control Circuit Low

Sources

• gsi.ext.gm.com: 14OBDG10 Engine Diagnostics
• gsi.ext.gm.com: 20OBDG04 Diagnostics
• static.nhtsa.gov: MC 10073689 2280
• static.nhtsa.gov: MC 10113171 9999

Values and procedures vary by manufacturer. If it affects brakes, steering, fuel or high voltage, see a professional. Updated: 2026-11-04. How we build these pages.