Fuel and air

P027B — Fuel Pump Module B Control Circuit Range/Performance

Severity: medium Drive with care, to a shop

What P027B means

The engine control module commands fuel pump module B (a driver or pump relay circuit) and compares that command with the circuit's actual response. P027B is stored when the control signal or feedback falls outside the expected range. The cause may be wiring, a connector, the module itself, or rarely the PCM.

Symptoms

  • Check Engine light on
  • Hard starting or no start
  • Loss of power or hesitation under acceleration
  • Rough running under load
  • Engine stalling while driving
  • Worse fuel economy

Possible causes

  1. Damaged, open or shorted wiring to fuel pump module B
  2. Corroded or loose connector pins, or a poor ground
  3. Faulty fuel pump module B or its driver
  4. Blown fuse or failed fuel pump relay
  5. Low system voltage from a weak battery or charging problem
  6. PCM fault or software issue (uncommon)

How to diagnose

  1. Scan all codes and freeze frame data, noting any other fuel or voltage codes
  2. Check the fuses and relays for the fuel pump B circuit
  3. Inspect the harness and connectors at the tank and module for corrosion, chafing or heat damage
  4. Measure battery and system voltage with the key on and while the pump runs
  5. Test power, ground and control signal at the module connector with a multimeter or scope
  6. Check the control wires for opens and shorts to ground or voltage
  7. Measure fuel pressure and compare it with factory specs
  8. Check pump resistance and current draw; if wiring is good, suspect the module, then the PCM

Common fixes

  • Repair the wiring and clean or replace the connectors
  • Replace a bad fuse or relay
  • Replace fuel pump module B or its driver
  • Update the PCM software if the manufacturer has a service bulletin
  • Replace or reprogram the PCM once it is confirmed faulty

P027B on different brands

GM
On GM vehicles with dual fuel pump modules, this code points to a problem in the control circuit of the second (B) pump module.

Questions and answers

What does P027B mean?

The PCM detected that the control circuit for fuel pump module B is operating out of range. Wiring, connectors or the pump module itself are the most common causes.

Can I drive with P027B?

Only briefly and carefully, for example to a shop. The engine may lose power or stall, which is unsafe on the road.

Should I replace the fuel pump right away?

No. First check the fuses, relay, power, ground and connectors, since the fault is often in the wiring rather than the module.

This is general information about the code. The meaning can differ between makes and models: a scan tool and the repair manual for your car will show the exact cause.