🚨 Diagnostic Profile
Make: Buick
Technical Description: Cruise Vehicle Speed/Set Speed Difference Too High
This diagnostic trouble code indicates that the Powertrain Control Module (PCM) or Electronic Brake Control Module (EBCM) has detected a significant discrepancy between the actual vehicle speed (as measured by the wheel speed sensors or vehicle speed sensor) and the speed requested by the cruise control system. This typically points to a mechanical throttle actuation problem, a wiring/sensor fault, or a module communication issue preventing the cruise system from accurately maintaining the set speed.
🚨 Repair Difficulty Tier
Tier: Intermediate
This repair requires a capable OBD-II scan tool with live data streaming capability (bi-directional preferred) and a digital multimeter to test wiring integrity and sensor voltage output. While no high-liability restraint systems are involved, proper diagnosis requires knowledge of throttle body actuation systems, wheel speed sensor circuits, and module communication networks (GMLAN/CAN bus). Most competent DIY mechanics with proper tools can attempt this, but intermittent electrical faults may require a professional-grade scanner for full resolution.
🛠️ Resolution Steps
Step 1: Preliminary Inspection
Begin with a visual inspection of the throttle body assembly, checking for carbon buildup, binding linkage, or a stuck throttle plate that could prevent the Electronic Throttle Control (ETC) system from matching commanded speed. Inspect wiring harnesses and connectors at the Throttle Position Sensor (TPS), Vehicle Speed Sensor (VSS), and all four wheel speed sensors for corrosion, chafing, or loose pins. Check for aftermarket wheel/tire size changes that could cause a speed calibration mismatch. Also inspect the throttle body electrical connector and ground straps near the engine bay for corrosion or looseness.
Step 2: Diagnostic Verification
Connect a scan tool and monitor live data parameters including Vehicle Speed (VSS), Commanded Throttle Position, Actual Throttle Position, and Wheel Speed Sensor readings from all four corners. Compare values while road testing to identify discrepancies exceeding manufacturer threshold (commonly greater than 1-2 MPH sustained difference). Use a multimeter to backprobe the TPS and VSS circuits, verifying reference voltage (usually 5V), ground continuity, and signal voltage changes with accelerator input. Check for stored freeze frame data and any companion codes (such as wheel speed sensor faults or throttle actuator control codes) that may point to a root cause. Perform a relative compression or mechanical throttle sweep test if ETC motor lag is suspected.
Step 3: Resolution & Reset Process
If a faulty wheel speed sensor or VSS is found, replace the specific sensor and clear the fault codes using the scan tool. If the throttle body shows carbon buildup or mechanical binding, clean the throttle plate and bore using approved throttle body cleaner, then perform a Throttle Body Relearn/Reset procedure through the scan tool’s special functions menu. If wiring faults are found, repair or replace the damaged harness section and reseal connectors with dielectric grease. After repairs, clear all DTCs, perform a battery disconnect/reconnect if required for module relearn, and road test the vehicle while re-engaging cruise control to confirm the set speed now matches actual vehicle speed without fault code recurrence.
📦 Parts, Labor, and Budget Estimates
Required Components/Software: Wheel Speed Sensor(s), Vehicle Speed Sensor (VSS), Throttle Body Assembly (if faulty), OBD-II Scan Tool with bi-directional control, Throttle Body Cleaner, Wiring Harness Repair Kit (if needed), Dealer-level scan tool software for module relearn procedures (GM MDI/Tech2 or equivalent).
Average Component Price: Wheel Speed Sensor: $40–$120 each | Vehicle Speed Sensor: $30–$90 | Throttle Body Assembly: $150–$350 | Wiring Repair Kit: $20–$60 | Dealer Programming/Relearn Fee (if required): $80–$150.
Estimated Labor Hours: Diagnostic Time: 1.0–1.5 hours | Wheel Speed Sensor Replacement: 0.5–1.0 hour per sensor | Throttle Body Replacement/Cleaning: 1.0–1.5 hours | Total Estimated Labor (Diagnosis + Repair): 2.0–3.5 hours depending on root cause identified.