🚨 Diagnostic Profile
Vehicle/Equipment Make: BUICK
Technical Description: A/C Evaporator Temperature Sensor Circuit High Voltage
This diagnostic trouble code indicates that the Heating, Ventilation, and Air Conditioning (HVAC) control module has detected an abnormally high voltage signal coming from the evaporator temperature sensor circuit. This sensor is critical because it monitors the temperature of the evaporator core to prevent it from freezing and to properly regulate cabin cooling output. A high voltage reading typically suggests an open circuit, a damaged sensor, or a wiring issue preventing the signal from grounding correctly.
🚨 Repair Difficulty Tier
Rating: Intermediate
This repair falls into the Intermediate category. While replacing the sensor itself is mechanically straightforward, accessing the evaporator core sensor often requires partial disassembly of the dashboard or HVAC housing. Additionally, a multimeter and a vehicle-specific scan tool are required to accurately test circuit resistance and view live sensor data to confirm the fault before replacing parts.
🛠️ Resolution Steps
Step 1: Preliminary Inspection
Begin by visually inspecting the wiring harness connector leading to the evaporator temperature sensor, usually located near the evaporator core inside the HVAC housing beneath the dashboard. Look for corrosion, bent pins, melted plastic, or a sensor connector that has become unseated. Check for any aftermarket wiring modifications or rodent damage along the harness route that could cause an open circuit.
Step 2: Diagnostic Verification
Connect an OBD-II scan tool capable of reading manufacturer-specific HVAC data (GM-specific scanner recommended) and monitor the live evaporator temperature sensor PID. A reading that is pegged at an extreme cold value (often -40°F) while the system is running typically confirms an open circuit or high resistance fault. Next, disconnect the sensor and use a digital multimeter to check the resistance across the sensor terminals; compare the reading to the manufacturer’s temperature-to-resistance chart. An infinite or out-of-range resistance reading confirms the sensor itself has failed. If the sensor tests within range, perform a continuity test on the wiring harness back to the HVAC control module to rule out a chafed wire or poor ground connection.
Step 3: Resolution & Reset Process
If the sensor has failed the resistance test, replace the evaporator temperature sensor with an OEM or OEM-equivalent replacement part. Ensure the connector is fully seated and locked after installation. If the wiring harness was found to be damaged, repair or replace the affected harness segment using proper automotive-grade soldering and heat-shrink tubing. After the repair, clear the stored diagnostic trouble codes using the scan tool and perform a test drive with the A/C system running to confirm the live data now reflects accurate, fluctuating evaporator temperatures and that the code does not return.
📦 Parts, Labor, and Budget Estimates
Required Components/Software: Evaporator temperature sensor, GM-compatible OBD-II scan tool, digital multimeter, wiring harness repair kit (if applicable).
Average Component Price: $15 – $45 for the sensor itself (OEM pricing may run slightly higher). Wiring harness repairs, if needed, are typically billed under labor rather than parts.
Estimated Labor Hours: 1.0 to 2.5 hours, depending on dashboard/HVAC housing disassembly required for sensor access on this specific Buick platform.