CMTC Incorrect Ambient Temperature Reading
- Using scan tool, select ENGINE, SENSORS. Select AMBIENT/BAT TMP DEG. Compare scan tool reading with actual outside temperature. If temperature readings do not match, go to next step. If temperature readings match, replace CMTC module. See appropriate ANALOG INSTRUMENT PANELS article.
- Disconnect and remove ambient/battery temperature sensor. Sensor is located behind front bumper, right of center. Using DVOM, measure resistance between sensor terminals and compare with AMBIENT/BATTERY TEMPERATURE SENSOR SPECIFICATIONS table. If resistance measurement does not correspond with specification, replace sensor. If sensor is within specification, go to next step.AMBIENT/BATTERY TEMPERATURE SENSOR SPECIFICATIONS
Ambient Temperature k/ohms 32°F (0°C) 29.3-36.0 50°F (10°C) 18.0-22.0 68°F (20°C) 11.4-13.6 77°F (25°C) 9.1-10.8 86°F (30°C) 7.4-8.7 104°F (40°C) 4.9-5.7 122°F (50°C) 3.3-3.8 - Turn ignition off. Close all vehicle doors and ensure all lights are off. Wait one minute. Using DVOM, measure resistance between ground and terminal No. 1 (Black/Light Blue wire) on ambient temperature/battery temperature sensor connector. If resistance is 5 ohms or greater, go to next step. If resistance is less than 10 ohms, go to 7.
- Connect ambient/battery temperature sensor. Disconnect Powertrain Control Module (PCM) connector C2. Using DVOM, measure resistance between terminals No. 43 (Black/Light Blue wire) and No. 52 (Pink/Yellow wire) on PCM harness connector. See Fig 1. Compare with AMBIENT/BATTERY TEMPERATURE SENSOR SPECIFICATIONS table. If resistance measurement does not correspond with specification, go to next step. If sensor is within specification, replace CMTC module. See appropriate ANALOG INSTRUMENT PANELS article.
- Disconnect ambient/battery temperature sensor. Using DVOM, measure resistance between ground and terminal No. 1 (Black/Light Blue wire) on sensor connector. If resistance is less than 500 k/ohms, repair Black/Light Blue wire for partial short to ground. If resistance is 500 k/ohms or greater, go to next step.
- Move ohmmeter lead to terminal No. 2 (Pink/Yellow wire) on sensor connector. If resistance is less than 500 k/ohms, repair Pink/Yellow wire for partial short to ground. If resistance is 500 k/ohms or greater, repair Pink/Yellow wire for short to Black/Light Blue wire.
- Disconnect Powertrain Control Module (PCM) Gray connector. Using DVOM, measure resistance of Black/Light Blue wire between PCM connector terminal No. 43 and ambient temperature/battery temperature sensor connector terminal No. 2. If resistance is 5 ohms or greater, repair open in Black/Light Blue wire. If resistance is less than 5 ohms, replace PCM. See POWERTRAIN CONTROL MODULE (PCM) under REMOVAL & INSTALLATION.