LEMON Manuals: Even more car manuals for everyone: 1960-2025
Home >> Jeep >> 1999 >> Cherokee Classic, 2.5 P >> Repair and Diagnosis >> Body & Frame >> Body, Cab Control Systems >> Body Control Computer - Tests >> CMTC Symptom Tests >> Incorrect Ambient Temperature Reading
April 5, 2026: LEMON Manuals is launched! Read the announcement.

Incorrect Ambient Temperature Reading

  1. Disconnect and remove ambient temperature sensor. Sensor is located behind front bumper, right of center. Using external ohmmeter, measure resistance between sensor terminals and compare with AMBIENT TEMPERATURE SENSOR SPECIFICATIONS  table. If resistance measurement does not correspond with AMBIENT TEMPERATURE SENSOR SPECIFICATIONS  table, replace sensor. If sensor is within specification, go to next step.
    AMBIENT 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
  2. Close all vehicle doors and ensure all lights are off. Wait one minute. Using external ohmmeter, measure resistance between ground and terminal No. 1 (Black/Light Blue wire) on ambient temperature sensor harness connector. If resistance is less than 5 ohms, go to next step. If resistance is 5 ohms or greater, go to 6)  .
  3. Connect ambient temperature sensor. Disconnect CMTC connector. Using external ohmmeter, measure resistance between terminals No. 4 and No. 10 on CMTC harness connector. Compare with AMBIENT TEMPERATURE SENSOR SPECIFICATIONS  table. If resistance measurement does not correspond with AMBIENT TEMPERATURE SENSOR SPECIFICATIONS table, go to next step. If sensor is within specification, replace CMTC module.
  4. Disconnect ambient temperature sensor. Using external ohmmeter, 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.
  5. Move ohmmeter lead to terminal No. 2 (Violet/Light Green wire) on sensor connector. If resistance is less than 500 k/ohms, repair Violet/Light Green wire for partial short to ground. If resistance is 500 k/ohms or greater, repair Violet/Light Green wire for short to Black/Light Blue wire.
  6. Using external ohmmeter, measure resistance of Black/Light Blue wire between terminal No. 10 on CMTC harness connector and terminal No. 2 on ambient temperature sensor harness connector. If resistance is less than 5 ohms, replace CMTC. If resistance is 5 ohms or greater, repair open Black/Light Blue wire.
scientia non olet · About LEMON Manuals