🚨 Diagnostic Profile
Vehicle/Equipment Make: BUICK
Technical Description: Accelerator Pedal Position (APP) Sensor 3 Circuit
This fault code indicates that the Powertrain Control Module (PCM) has detected an electrical irregularity—such as an open circuit, short to ground, short to voltage, or signal correlation error—on the third internal sensor circuit of the Accelerator Pedal Position assembly. Modern electronic throttle control (ETC) systems use three redundant signals from the pedal sensor to ensure safety; if Sensor 3 disagrees with Sensors 1 and 2, the module may limit engine power (Limp Mode) to prevent unintended acceleration.
🚨 Repair Difficulty Tier
Classification: [Intermediate]
This repair falls into the Intermediate category. While replacing the physical pedal assembly is mechanically simple (usually just two bolts and an electrical connector), accurately diagnosing why the circuit failed requires a digital multimeter (DMM) to check reference voltages and ground circuits, as well as a scan tool capable of reading live PCM data (Mode $06 or enhanced live data) to compare the three sensor signals in real-time.
🛠️ Resolution Steps
Step 1: Preliminary Inspection
- Visually inspect the wiring harness connector at the base of the accelerator pedal for corrosion, bent pins, or moisture intrusion.
- Check for any aftermarket wiring modifications, rodent damage, or chafing along the harness route under the dash.
- Inspect the pedal assembly itself for physical damage, excessive play, or binding that could affect the internal potentiometers/hall-effect sensors.
Step 2: Diagnostic Verification
- Connect a scan tool and monitor live data PIDs for APP Sensor 1, 2, and 3 simultaneously while slowly depressing the pedal from 0% to 100%.
- Verify that all three signals move in a smooth, proportional, and correlated manner (no sudden drops, flatlines, or erratic voltage spikes).
- Using a DMM, back-probe the connector (key on, engine off) to confirm the 5-volt reference voltage and clean ground are present at the Sensor 3 circuit pins.
- Wiggle-test the harness while monitoring voltage to identify intermittent opens or shorts.
Step 3: Resolution & Reset Process
- If wiring/connector issues are found, repair or replace the damaged harness section and secure with factory-correct connectors.
- If the sensor circuit itself tests faulty internally, replace the complete Accelerator Pedal Sensor Assembly (these are non-serviceable as individual sensors).
- Clear the Diagnostic Trouble Codes (DTCs) using the scan tool.
- Perform a Throttle/Pedal Relearn procedure if specified by the service manual, and complete a test drive through multiple throttle ranges to confirm the code does not return.
📦 Parts, Labor, and Budget Estimates
Required Components/Software: OEM Accelerator Pedal Sensor Assembly, Wiring Pigtail/Connector Repair Kit (if applicable), Digital Multimeter, OEM-level or advanced aftermarket scan tool with bi-directional live data capability.
Average Component Price: $75 – $220 USD for the pedal sensor assembly (OEM parts tend to run higher than aftermarket); wiring repair kits typically range from $15 – $40 USD.
Estimated Labor Hours: 0.5 – 1.5 hours for diagnosis and sensor replacement; add 0.5 hours if wiring harness repair is required due to additional testing and splicing time.