🚨 Diagnostic Profile
Vehicle/Equipment Make: Buick
Technical Description: APP Sensor 1-2 Performance
This diagnostic trouble code indicates that the Powertrain Control Module (PCM) has detected a disagreement or implausible signal correlation between the two internal circuits of the Accelerator Pedal Position (APP) sensor. Modern Buick models use a dual or triple-sensor assembly on the accelerator pedal to ensure redundant safety signals are sent to the Electronic Throttle Control (ETC) system. When Sensor 1 and Sensor 2 voltages do not track together as expected (based on pre-programmed ratios), the module flags a performance fault to prevent unintended acceleration, often resulting in a ‘Reduced Engine Power’ message on the driver information center.
🚨 Repair Difficulty Tier
Tier Rating: [Intermediate]
While the physical replacement of the accelerator pedal assembly is mechanically simple (usually just two to three mounting bolts and an electrical harness clip), accurately diagnosing this specific fault requires an intermediate skill level. The technician must use a scan tool capable of reading live, bi-directional data for both sensor circuits simultaneously to confirm a voltage discrepancy versus a simple wiring short. Basic hand tools are needed for replacement, but a multimeter and live-data scanner are mandatory for an accurate diagnosis to avoid unnecessary parts replacement.
🛠️ Resolution Steps
Step 1: Preliminary Inspection
Begin by visually inspecting the wiring harness connector located underneath the accelerator pedal assembly. Look for corrosion, bent pins, or chafing in the wiring insulation caused by rubbing against the driver’s side kick panel or carpet. Check for any aftermarket floor mats that may be obstructing or pressing on the pedal assembly, as this can sometimes cause mechanical binding that affects sensor readings.
Step 2: Diagnostic Verification
Connect an OBD-II scan tool capable of enhanced GM/Buick data streams. Monitor the Parameter IDs (PIDs) for ‘APP Sensor 1’ and ‘APP Sensor 2’ simultaneously while slowly depressing the pedal from 0% to 100%. In a healthy system, Sensor 1 typically reads roughly half the voltage of Sensor 2 at any given pedal position (e.g., Sensor 1 reads 0.8V while Sensor 2 reads 1.6V). If the voltages fail to maintain this ratio, jump to a value, or one sensor remains flat while the other moves, this confirms an internal sensor fault rather than a wiring issue. Follow this with a multimeter check at the harness connector (key on, engine off) to verify the 5-volt reference signal and ground circuits are stable and not fluctuating.
Step 3: Resolution & Reset Process
If data confirms an internal sensor correlation failure, the entire accelerator pedal assembly must be replaced, as the sensors are not sold or serviced individually. Disconnect the negative battery terminal, unbolt the pedal assembly from the firewall, and transfer any trim pieces to the new unit. After installing the new assembly and reconnecting the battery, use the scan tool to clear the Diagnostic Trouble Codes (DTCs). It is highly recommended to perform a ‘Throttle Body Relearn’ or idle relearn procedure using the scan tool to allow the PCM to recalibrate the new pedal’s minimum and maximum voltage parameters, ensuring smooth throttle response.
📦 Parts, Labor, and Budget Estimates
Required Components/Software: OEM Accelerator Pedal Position Sensor Assembly, Scan tool with bi-directional live data capability (e.g., Tech2, MDI2, or equivalent aftermarket scanner).
Average Component Price: $95 – $220 USD (depending on specific Buick model year and trim level).
Estimated Labor Hours: 0.5 – 0.8 hours for diagnosis and replacement (Standard book time often combines diagnosis with the physical R&R of the pedal assembly).