On demand-controlled fuel systems the engine module does not drive the pump itself but sends a pump control module the desired pump output on a separate control line, usually as a duty cycle; the module reports back on a monitor line or via CAN. Module B is a second pump module, for example on dual-tank commercial vehicles. P027A is the counterpart of P025A: the control line from the engine module to pump module B is open or faulty. No manufacturer using P027A was found – Ford reports line faults of both modules together under P025A, GM only uses P025A; the description follows CARB's circuit monitoring requirement and Ford's module B check. If the second tank's pump gets no valid command, fuel may run short when running from that tank.
Medium severity. Can I keep driving?Avoid long trips and hard acceleration. If you smell fuel or the car stalls, do not continue.
Symptoms
- Check engine light (manufacturer-dependent)
- Fuel shortage when running from the second tank
- Starting problems, surging
Most likely causes
- Control line to the pump module open or shorted, often along the frame
- Connector at the pump module corroded or wet (module often mounted on the frame)
- Pump control module faulty (input)
- Module ground or supply poor
What to check, in order
Start with the simplest. You can tick off each step.
Good to know
- Repair difficulty: medium
- It affects emissions.
What each character of P027A means
- P: Powertrain: engine and transmission
- 0: Generic code: same on every make
- 2: Fuel injection
- 7A: Specific fault in that system
Frequently asked questions
Can I keep driving with code P027A?
Avoid long trips and hard acceleration. If you smell fuel or the car stalls, do not continue.
What causes code P027A?
The most common causes are: control line to the pump module open or shorted, often along the frame; connector at the pump module corroded or wet (module often mounted on the frame); pump control module faulty (input).
Related codes
- P025AFuel Pump Module A Control Circuit/Open
- P027BFuel Pump Module B Control Circuit Range/Performance
- P027CFuel Pump Module B Control Circuit Low
- P027DFuel Pump Module B Control Circuit High
- P2632Fuel Pump B Control Circuit/Open
- P26EAFuel Pump Control Module B
Sources
- law.cornell.edu: 13 CCR 1968.2
- fordservicecontent.com: OBD Operations Summary Gasoline 2020 2023
- roushcleantech.com: Roush CleanTech Diagnostics Manual DA 8.5.18
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.