🚨 Diagnostic Profile
Vehicle/Equipment Make: BUICK
Technical Description: Throttle Actuator Control (TAC) Module Throttle Actuator Position Performance
This diagnostic trouble code indicates that the Engine Control Module (ECM) has detected a discrepancy between the commanded throttle actuator position and the actual position reported by the throttle position sensors within the electronic throttle body. This is typically related to the dual Throttle Position (TP) sensors not correlating properly, mechanical binding of the throttle plate, or internal TAC module/throttle body circuit faults.
🚨 Repair Difficulty Tier
Difficulty Rating: Intermediate
This repair requires a bi-directional capable scan tool to read live TP sensor data, perform throttle relearn/reset procedures, and verify actuator duty cycle commands. While not as liability-heavy as airbag or restraint system work, incorrect diagnosis or improper relearn procedures can result in poor drivability, limp-home mode, or throttle response issues. A standard mechanic with intermediate electrical diagnostic skills and an enhanced scan tool (not just a basic code reader) can typically perform this repair.
🛠️ Resolution Steps
Step 1: Preliminary Inspection
Begin with a visual inspection of the throttle body assembly, checking for any carbon buildup, debris, or physical obstruction on the throttle plate that could prevent it from moving freely. Inspect the electrical harness and connector at the throttle body for corrosion, bent pins, chafed wiring, or loose connections. Check the TAC module wiring harness for signs of heat damage or rodent intrusion, as these are common culprits in Buick platforms. Also inspect the throttle body mounting for looseness or vacuum leaks around the gasket.
Step 2: Diagnostic Verification
Connect a capable scan tool and access live data parameters for TP Sensor 1 and TP Sensor 2 percentages. At idle (throttle closed), both sensors should read a low, consistent percentage (typically under 5%), and they should move in a complementary, linear fashion as you command throttle input (if using a bi-directional tool) or press the accelerator with the engine off and key on. Use a digital multimeter to back-probe the 5-volt reference, signal, and ground circuits at the throttle body connector to confirm proper voltage supply (typically 5V reference and sweeping signal voltage from approximately 0.5V to 4.5V). Check for any correlating Accelerator Pedal Position (APP) sensor codes, as this can point to a wiring or module-side issue rather than a throttle body fault. Compare live data to known-good specifications in service information for the exact model year.
Step 3: Resolution & Reset Process
If the throttle body assembly has failed internally (sticking, sensor drift, or damaged actuator motor), replace the electronic throttle body assembly as a unit, as individual components are not typically serviceable. After installation, clear all stored DTCs and perform a throttle body relearn/reset procedure using the scan tool, which typically involves commanding a Throttle Plate Reset or Idle Learn procedure with the key on, engine off, and all accessory loads off. Reconnect the battery (if disconnected) and allow the ECM to complete its idle relearn with the engine running at normal operating temperature. Test drive the vehicle under varying throttle conditions to confirm the TP sensor correlation remains within spec and that no codes return.
📦 Parts, Labor, and Budget Estimates
Required Components/Software: Electronic Throttle Body Assembly (includes integrated TAC motor and dual TP sensors), throttle body gasket/seal, enhanced bi-directional scan tool capable of throttle relearn procedures, digital multimeter.
Average Component Price: $150 – $350 for an OEM or OEM-equivalent electronic throttle body assembly, depending on the specific Buick model and year. Aftermarket units may range slightly lower ($100 – $250).
Estimated Labor Hours: 0.5 to 1.0 hour for diagnosis, plus 0.8 to 1.5 hours for throttle body replacement and relearn procedure, totaling approximately 1.3 to 2.5 hours of shop labor depending on accessibility and specific engine platform.