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DTC codes / P02xx · Fuel and air metering (injector circuits) / P027A

P027AFuel Pump Module B Control Circuit/Open

P027A indicates that the powertrain control module (PCM) has detected an open circuit or excessive resistance in the control circuit for fuel pump module B, which is typically the secondary or auxiliary fuel pump on vehicles with a dual-pump system. The PCM commands the pump on and monitors the circuit for expected voltage or current feedback, and when the feedback falls outside the expected range, it sets this code and may disable the pump circuit to protect the driver.

SystemPowertrain
Code typeGeneric (all makes)
SeverityMedium
Fix difficultyIntermediate
AreaFuel and air metering (injector circuits)

Symptoms you may notice

  • Illumination of the check engine light, often with no other symptoms besides the warning light
  • Engine cranks but fails to start or starts only after prolonged cranking, especially when the secondary pump is needed for cold starts or high demand
  • Reduced engine power or a stumble under heavy acceleration or high fuel demand conditions
  • Intermittent stalling or a sudden loss of power while driving, particularly when the fuel level is low or the tank is nearly empty
  • A noticeable whine or absence of the usual fuel pump prime sound when the ignition is turned on
  • Possible lean fuel trim codes or misfire codes stored alongside P027A if the secondary pump cannot supply adequate fuel

Common causes, most likely first

  1. A damaged, corroded, or disconnected electrical connector at the fuel pump module B, often caused by water intrusion or road debris
  2. A broken or chafed wire in the control circuit between the PCM and the fuel pump module, frequently at flex points or near sharp edges
  3. A failed fuel pump module B itself, where the internal motor or control electronics have an open circuit
  4. A faulty fuel pump control module (FPCM) or relay that supplies power or ground to the pump circuit, if the vehicle uses a separate controller
  5. Corrosion or loose pins at the PCM connector, leading to an intermittent open circuit on the control wire
  6. A blown fuse or fusible link in the fuel pump B power circuit, though this often sets additional codes
  7. Aftermarket alarm or remote start wiring that has been spliced into the fuel pump circuit and created an open connection

How to diagnose and fix it

  1. Verify the code with a scan tool and check for any related pending or stored codes that might indicate a power or ground issue affecting the entire fuel pump system
  2. Inspect the fuel pump module B electrical connector for corrosion, loose pins, or water intrusion, and clean or repair as needed
  3. Perform a visual inspection of the control circuit wiring from the PCM to the pump, looking for chafing, breaks, or poor splices, and repair any damage
  4. Check the fuel pump B fuse and relay, and test the relay operation with a multimeter or by swapping with a known-good relay of the same type
  5. Measure resistance and voltage on the control circuit at the pump connector while commanding the pump on with a scan tool, comparing to manufacturer specifications
  6. If the circuit tests good, remove and bench-test the fuel pump module B, or substitute a known-good unit to confirm the fault
  7. Clear the code and perform a road test, including a cold start and a heavy acceleration run, to verify the repair and ensure the code does not return

What a P027A often really means

  • A loose or corroded ground connection at the fuel pump module B can mimic an open control circuit, so always check grounds before condemning the pump.
  • On many vehicles, fuel pump module B only runs under specific conditions such as low fuel level or high engine load, so the code may not set during a simple idle test.
  • Aftermarket remote starters or alarm systems spliced into the fuel pump wiring are a frequent cause of intermittent open circuits that set P027A.
  • A failing fuel pump control module (FPCM) can set P027A even when the pump itself is good, so test the control module output before replacing the pump.
  • The code can be set by a momentary open circuit during a bump or vibration, so a wiggle test of the harness while monitoring live data is often more revealing than a static resistance check.

Can I keep driving with P027A?

You can usually drive the vehicle with P027A set, but avoid heavy acceleration, towing, or running the fuel tank very low because the secondary pump may be needed for adequate fuel supply. If the engine stalls or loses power, pull over safely and have the vehicle towed to avoid a dangerous situation.

Tools that help

Tools we recommend are in the Auto Veteran shop on Amazon. As an Amazon Associate we earn from qualifying purchases.

Guidance is general and written for all OBD-II vehicles. Exact tests and values vary by model, so confirm the fault before replacing parts.

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