Fuel and air

P027C — Fuel Pump Module B Control Circuit Low

Severity: medium Drive with care, to a shop

What P027C means

P027C means the engine control module detected low voltage or an incorrect signal in the control circuit of Fuel Pump Module B. The ECM, or a separate pump driver, normally commands pump output with a control signal and compares it with feedback. When that signal falls below the expected range, fuel pressure may not match demand and the code is set.

Symptoms

  • Check Engine light on
  • Hard starting or long cranking
  • Hesitation or stumbling under load
  • Reduced power
  • Rough idle
  • Stalling from intermittent fuel pressure loss

Possible causes

  1. Damaged wiring or corroded connectors in the control circuit
  2. Failed Fuel Pump Module B
  3. Faulty fuel pump relay
  4. Poor ground, weak battery or charging problem
  5. Failed ECM (uncommon)

How to diagnose

  1. Scan for all codes and review freeze frame data, looking for other fuel or voltage codes
  2. Test battery condition and charging voltage
  3. Inspect the pump fuses and relay, and swap in a known good relay if needed
  4. Inspect the harness and connector at the pump module for corrosion, chafing, and moisture
  5. Check power and ground at the pump module connector with a multimeter
  6. Check the ECM control signal with a scope or a scan tool active test
  7. Measure fuel pressure with a gauge
  8. If wiring is good, test the pump module, then consider the ECM

Common fixes

  • Repair or replace damaged wiring and connectors
  • Replace the fuel pump relay
  • Replace Fuel Pump Module B
  • Service the battery and charging system, and clean ground connections
  • Replace or reprogram the ECM (rare)

Questions and answers

What does P027C mean?

It means the control circuit for Fuel Pump Module B has a low signal. Wiring, the relay, or power supply is more often to blame than the pump itself.

Can I drive with P027C?

Only briefly and with care. The car may lose power or stall on the road, so repair it soon.

What should I check first for P027C?

Start with the battery, fuses, fuel pump relay, and the connector and ground at the pump module. These checks are simple and often find the cause.

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.