B1946

Step 1: Locate the post-evaporator temperature sensor (typically mounted on the evaporator housing or in the outlet tube near the firewall) and visually inspect the sensor, connector, and wiring for physical damage, corrosion, water intrusion, or disconnected terminals

Step 2: Using a digital multimeter, backprobe the sensor connector and measure the resistance across the sensor terminals with ignition off; compare readings to manufacturer specifications (typically 2-5k ohms at room temperature for NTC thermistors)

Step 3: Check for proper reference voltage at the sensor connector with ignition on (typically 5V reference) and verify ground circuit continuity to the climate control module using a multimeter; resistance should be less than 1 ohm

Step 4: If voltage and ground are present but sensor readings are out of range, substitute a known-good sensor or use a resistance decade box to simulate sensor values and verify the climate control module responds appropriately

Step 5: Clear the code and operate the A/C system through multiple cooling cycles while monitoring live data for sensor temperature readings; verify the sensor responds to temperature changes and remains within normal parameters (typically 32-50°F during operation)

Step 6: If all circuits and sensor test good but code persists, perform voltage drop testing on the sensor power and ground circuits under load, and consider climate control module internal fault requiring module replacement