P027D

Code

Generic P — Powertrain

Fuel Pump Module B Control Circuit High

Brand: Generic

Type: P — Powertrain

Views: UK: 23 EN: 34 RU: 22

AI status

Completed

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Page language: EN

Causes

Short to battery voltage on the Fuel Pump Module B control wire
Faulty fuel pump module B (internal driver or wiring inside module)
Stuck/closed fuel pump relay or relay contact welded
Open or poor ground for the pump driver or PCM
Corroded/loose connector or damaged wiring harness
PCM or body control module output driver fault

Symptoms

Malfunction Indicator Lamp (MIL) illuminated
Fuel pump will not operate correctly (may run continuously or not at all)
Hard start, no start, or stalling under load
Low or erratic fuel rail pressure
Intermittent drivability issues tied to fuel delivery
Possible battery drain if pump runs continuously

What to check

Retrieve DTCs and freeze-frame data with a scan tool; check for related codes
Visually inspect wiring, connectors, and seals at the fuel pump module and relay/fuse box
Check relevant fuses and fuel pump relay operation
Measure control circuit voltage at the pump connector with ignition ON and during cranking
Perform continuity/resistance checks between pump control pin and PCM/driver pin
Check for short to battery: measure resistance from control wire to battery positive (key off)

Signal parameters

Expected inactive control voltage: near 0 V if the module is low-side switched; if module uses high-side switching, expected inactive is near 0–1 V (vehicle-specific)
Expected active control: pulsed or steady signal up to battery voltage (0–12 V) depending on command (usually PWM for speed control)
Fault condition: voltage higher than expected when command should be low (measured significantly above expected idle voltage, often near VBAT)
Typical PWM frequency range (if used): commonly 20–200 Hz (manufacturer-specific)

Diagnostic algorithm

Confirm code: read stored/active codes and freeze-frame; note operating conditions when code set.
Clear codes and attempt to reproduce. Monitor if P027D returns and under what conditions (KOEO, cranking, running).
Inspect connectors, wiring harness, protective grommets and routing to the fuel tank for melted insulation, chafing, or moisture intrusion.
With ignition ON (engine OFF), back-probe the pump module B control terminal and measure voltage. Note voltage with the module connected and disconnected.
If control circuit is high with the module disconnected, suspect a short to battery in the wiring, relay stuck closed, or a controller output forced high. Trace wiring toward relay/PCM and test continuity to battery positive.
If control circuit is normal when module disconnected but high when connected, suspect a fault inside the pump module B. Check pump current draw and bench-test or replace module if necessary.
Inspect/test the fuel pump relay: remove relay and check if control voltage clears; swap with known-good relay if available.
Verify PCM/BCM driver operation: check for software updates, TSBs, and test driver output per manufacturer diagnostic procedures. Replace controller only after wiring and module are confirmed good.
Repair any wiring damage, clean/repair connectors, replace defective pump module or relay, then clear codes and retest for proper operation before returning vehicle to service.

Likely causes

Control wire shorted to constant 12 V at a connector or chafed harness
Failed pump module with internal electronics pulling the line high
Relay contacts welded closed supplying battery voltage to the control line
Poor ground at pump module or module-to-chassis ground causing abnormal voltage
Faulty PCM or module driver issuing incorrect high output

Fault status

⚠️ Status

P027D — Fuel Pump Module B Control Circuit High: PCM detected voltage higher than expected on Fuel Pump Module B control circuit. Possible short to battery, failed module, relay stuck closed, or controller output fault.

🟡 Repair difficulty: Medium

⏱️ Diagnostic time: 1.0-3.0 hours