🚨 Diagnostic Profile
Make: BUICK
Code/Technical Description: Accelerator Pedal Position Sensor 2 Circuit Low Voltage
This diagnostic trouble code indicates that the Powertrain Control Module (PCM) has detected a voltage reading from the Accelerator Pedal Position (APP) Sensor 2 circuit that is lower than the expected calibrated range. Most Buick models use a triple-redundant pedal sensor system (Sensor 1, 2, and 3) for safety purposes within the electronic throttle control (drive-by-wire) system. A low voltage reading on Sensor 2 specifically points toward a wiring short to ground, a failing internal sensor resistor, or a corroded connector at the base of the accelerator pedal assembly.
🚨 Repair Difficulty Tier
Tier: [Intermediate]
While replacing the physical pedal assembly is mechanically simple (usually 2-3 bolts and an electrical connector), accurately diagnosing which of the three internal sensors is faulty requires a capable scan tool to view live data PIDs (Parameter IDs) for all three voltage signals simultaneously. A standard multimeter is also required to test wiring integrity. This is not a simple visual DIY fix due to the necessity of cross-referencing live voltage data against OEM specifications to avoid misdiagnosis.
🛠️ Resolution Steps
Step 1: Preliminary Inspection
Begin by visually inspecting the wiring harness connector located at the base of the accelerator pedal assembly inside the driver’s footwell. Look for:
- Corrosion or green oxidation on the pins.
- Pinched or chafed wiring where the harness meets the floor pan.
- Loose or unseated connector locks.
- Any aftermarket wiring (such as remote starters) that may be tapped into the harness incorrectly.
Step 2: Diagnostic Verification
Connect an OBD-II scan tool capable of reading live data streams. Navigate to the PCM data list and locate the following PIDs:
- APP Sensor 1 Voltage (Typically ranges from 0.5V to 4.5V)
- APP Sensor 2 Voltage (Typically runs roughly half of Sensor 1’s voltage, e.g., 0.25V to 2.25V)
Slowly press the accelerator pedal from idle to Wide Open Throttle (WOT) while watching the data. If Sensor 2 stays near 0V or does not rise in a smooth, linear ratio compared to Sensor 1, this confirms an internal sensor fault or wiring short. Backprobe the connector with a multimeter to check for a steady 5V reference voltage and a clean ground to rule out a wiring harness issue before condemning the sensor unit.
Step 3: Resolution & Reset Process
If wiring and connectors test positive (no corrosion/shorts) but the voltage ratio remains incorrect, the accelerator pedal assembly (which houses all sensors as one sealed unit) must be replaced. Unbolt the old assembly, transfer the wiring harness connector to the new unit, and torque the mounting bolts to OEM specifications.
Once replaced, clear the Diagnostic Trouble Codes (DTCs) using the scan tool. It is highly recommended to perform a Throttle Body Relearn/Reset procedure via the scan tool to allow the PCM to recalibrate idle airflow and pedal mapping to the new sensor unit. Perform a test drive to ensure the Check Engine Light does not return and that throttle response is smooth.
📦 Parts, Labor, and Budget Estimates
Required Components/Software: OEM Accelerator Pedal Assembly (integrated sensor unit), Bi-directional OBD-II Scan Tool (for live data and relearn procedures), Digital Multimeter.
Average Component Price: $80 – $180 USD for the OEM/Dealer pedal assembly.
Estimated Labor Hours: 0.5 to 1.0 hours (Book time for diagnosis and replacement is typically low, though full diagnostic time investigating wiring may add 0.5 hours if the fault is intermittent).