Code P129D Chevrolet: Fuel Pump Power Control Module Fault
Meaning
This code indicates an electrical problem in the activation circuit of the Fuel Pump Power Control Module (FPM). The module detects an abnormally low voltage (< calibrated value) for more than 1 second on its power supply circuit, triggering the check engine light.
Probable Causes
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FPM Module Failure (Fuel Pump Power Control Module).
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Wiring Problems:
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Open circuit or short circuit in the module harness.
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Faulty electrical connections (oxidized, loose, bent, or broken pins).
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Degraded Power Supply:
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Insufficient or intermittent supply voltage.
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Common Symptoms
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🔴 Check Engine Light On (“Service Engine Soon”).
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🚗 Starting Problems or random stalling.
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⚡️ Unstable Idle or loss of power during acceleration.
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⛽️ Fuel Pump Malfunctions (abnormal humming, cut-outs).
Diagnostic Procedure
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Visual Inspection of Circuits:
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Check the harness and connectors associated with the FPM.
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Look for: damaged cables, corrosion, deformed or oxidized pins.
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Electrical Checks:
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Test the module’s supply voltage with a multimeter.
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Measure continuity and check for the absence of short circuits in the circuits.
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Inspect associated fuses and grounds.
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FPM Module Diagnosis:
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If the circuits are intact, suspect an internal module failure.
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Use a scanner to analyze live data and associated codes.
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Corrective Actions
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🔧 Repair faulty circuits (soldering, harness replacement).
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🔌 Clean or replace damaged connectors.
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⚠️ Replace the FPM Module if faulty (after eliminating other causes).
Important: This fault can lead to a sudden engine shutdown. Prompt intervention is recommended. Consult the vehicle’s electrical diagrams for an accurate diagnosis.
Technical Note: The FPM module manages the fuel pump’s power supply via a relay. A low voltage prevents it from activating the pump correctly, risking damage to the fuel system.