šØ Diagnostic Profile
Vehicle/Equipment Make: BUICK
Technical Description: Accelerator Pedal Position Sensor 3 Circuit High Voltage
This diagnostic trouble code indicates that the Engine Control Module (ECM) or Powertrain Control Module (PCM) has detected a voltage signal from the Accelerator Pedal Position (APP) Sensor 3 circuit that exceeds the normal expected operating range. Most electronic throttle systems use three APP sensors for redundancy and safety cross-checking. A ‘High Voltage’ fault typically points to an open circuit, a short to a voltage source (like the 5V reference wire shorting to the signal wire), a failing sensor, or a corroded/damaged connector at the accelerator pedal assembly.
šØ Repair Difficulty Tier
Difficulty Rating: Intermediate
This repair falls into the Intermediate category. While the physical replacement of the accelerator pedal assembly is mechanically straightforward (usually just a few bolts and an electrical connector), accurately diagnosing which of the three internal sensors is at fault requires a capable scan tool to view live data (PIDs) for all three APP sensor voltages simultaneously. A basic multimeter is also required to test circuit continuity and resistance if wiring is suspected rather than the sensor assembly itself. No high-level module programming is typically required unless the ECM/PCM itself needs a relearn procedure after replacement.
š ļø Resolution Steps
Step 1: Preliminary Inspection
Begin with a visual inspection of the accelerator pedal assembly, typically located under the dash near the driver’s footwell. Check the wiring harness and connector for signs of corrosion, pushed-out pins, chafing, or pinched wires. Inspect the connector lock tab to ensure it is fully seated. Look for any aftermarket floor mats or debris that may have interfered with the pedal sensor assembly. Also check for any recent wiring repairs or rodent damage near the harness routing from the pedal to the engine bay.
Step 2: Diagnostic Verification
Connect a professional-grade scan tool capable of reading GM-specific live data streams. Monitor APP Sensor 1, 2, and 3 voltages simultaneously while slowly depressing and releasing the pedal. A healthy sensor 3 circuit should typically read within GM-specified voltage ranges (often around 0.5Vā4.5V, but confirm with service information for the exact model year). If Sensor 3 reads at or near 5V (reference voltage) constantly, this suggests a short to the 5V reference circuit or an internal sensor fault. Backprobe the connector with a digital multimeter to check the 5V reference, ground, and signal wires independently with the key on, engine off (KOEO). Check for a short to voltage or an open ground circuit.
Step 3: Resolution & Reset Process
If wiring and connectors test within specification but the fault persists, replace the entire Accelerator Pedal Position Sensor Assembly, as GM typically does not sell individual internal sensors separately. After replacement, clear the Diagnostic Trouble Codes (DTCs) using the scan tool. Perform a key cycle (key off, wait 30 seconds, key on) to allow the ECM/PCM to re-initialize and run its internal sensor rationality checks. Conduct a test drive while monitoring live APP sensor data to confirm stable voltage output across the full pedal travel range and ensure the Check Engine Light (MIL) does not return.
š¦ Parts, Labor, and Budget Estimates
Required Components/Software: Accelerator Pedal Position Sensor Assembly, OEM-grade electrical connector/pigtail (if wiring damage is found), GM-capable bi-directional scan tool for live data monitoring.
Average Component Price: $80 – $220 USD for the OEM or quality aftermarket pedal assembly, depending on trim level and model year.
Estimated Labor Hours: 0.5 – 1.2 hours for diagnosis and replacement, assuming no extensive wiring repair is needed. Add 0.5 hours if harness repair or splicing is required.