Diagnostic Test

WARNING: This page is about a different car, the 2016 Jeep Wrangler and 2015 Jeep Wrangler. However, it is still accessible from the selected car via links, so may be relevant.

CHECK (C21) EVAPORATOR TEMPERATURE SENSOR SIGNAL CIRCUIT VOLTAGE
1. Ignition on, engine not running.
2. With the scan tool, read HVAC DTCs.
  Is this DTC active?
  
  Yes
  - Go To 2
  No
  - Go To 7
CHECK THE (C21) EVAPORATOR TEMPERATURE SENSOR SIGNAL CIRCUIT VOLTAGE

Fig 1: Measuring Evaporator Temperature Sensor Signal Circuit Voltage
Courtesy of CHRYSLER GROUP, LLC
1. Turn the ignition off to the lock position.
2. Disconnect the Evaporator Temperature Sensor harness connector.
  NOTE:
  Due to the small terminal and pin size of the Evaporator Temperature Sensor and harness connector, make sure to not damage the terminals in this process.
3. Connect a jumper wire between the (C21) Evaporator Temperature Sensor Signal circuit and the (C121) Sensor Ground circuit in the Evaporator Temperature Sensor harness connector.
4. Ignition on, engine not running.
5. With the scan tool, read the Evaporator Temperature Sensor voltage.
  Is the voltage below 0.1 of a volt?
  
  Yes
  - Replace the Evaporator Temperature Sensor in accordance with the Service Information. Refer to SENSOR, EVAPORATOR TEMPERATURE, REMOVAL .
  - Perform the HVAC VERIFICATION TEST. Refer to STANDARD PROCEDURE .
  No
  - Go To 3
CHECK THE (C21) EVAPORATOR TEMPERATURE SENSOR SIGNAL CIRCUIT FOR A SHORT TO VOLTAGE

Fig 2: Checking Evaporator Temperature Sensor Signal Circuit For A Short To Voltage
Courtesy of CHRYSLER GROUP, LLC
1. Turn the ignition off to the lock position.
2. Disconnect the jumper wire from the Evaporator Temperature Sensor harness connector.
3. Disconnect the A/C Heater Control C1 harness connector.
4. Ignition on, engine not running.
5. Measure the voltage of the (C21) Evaporator Temperature Sensor Signal circuit.
  Is there any voltage present?
  
  Yes
  - Repair the (C21) Evaporator Temperature Sensor Signal circuit for a short to voltage.
  - Perform the HVAC VERIFICATION TEST. Refer to STANDARD PROCEDURE .
  No
  - Go To 4
CHECK THE (C21) EVAPORATOR TEMPERATURE SENSOR SIGNAL CIRCUIT FOR AN OPEN

Fig 3: Checking Evaporator Temperature Sensor Signal Circuit For An Open
Courtesy of CHRYSLER GROUP, LLC
1. Turn the ignition off to the lock position.
2. Measure the resistance of the (C21) Evaporator Temperature Sensor Signal circuit between the A/C Heater Control C1 harness connector and the Evaporator Temperature Sensor harness connector.
  Is the resistance above 1.0 Ohm?
  
  Yes
  - Repair the (C21) Evaporator Temperature Sensor Signal circuit for an open or high resistance.
  - Perform the HVAC VERIFICATION TEST. Refer to STANDARD PROCEDURE .
  No
  - Go To 5
CHECK THE (C121) SENSOR GROUND CIRCUIT FOR AN OPEN

Fig 4: Checking Sensor Ground Circuit For An Open
Courtesy of CHRYSLER GROUP, LLC
1. Measure the resistance of the (C121) Sensor Ground circuit between the A/C Heater Control C1 harness connector and the Evaporator Temperature Sensor harness connector.
  Is the resistance above 1.0 Ohm?
  
  Yes
  - Repair the (C121) Sensor Ground circuit for an open.
  - Perform the HVAC VERIFICATION TEST. Refer to STANDARD PROCEDURE .
  No
  - Go To 6
CHECK THE EVAPORATOR TEMPERATURE SENSOR
1. Replace the Evaporator Temperature Sensor in Accordance with the Service Information. Refer to SENSOR, EVAPORATOR TEMPERATURE, REMOVAL .
2. Cycle the ignition off for 30 seconds then back on.
3. With the scan tool, read HVAC DTCs.
  Does this DTC reset?
  
  Yes
  - Replace and program the A/C Heater Control in accordance with the Service Information. Refer to CONTROL, A/C AND HEATER, REMOVAL .
  - Perform the HVAC VERIFICATION TEST. Refer to STANDARD PROCEDURE .
  No
  - Test complete.
  - Perform the HVAC VERIFICATION TEST. Refer to STANDARD PROCEDURE .
CHECK THE WIRING AND CONNECTORS
1. The conditions necessary to set the DTC are not present at this time.
2. With the scan tool, check the Environmental Data to help identify the conditions in which the DTC was set.
3. Using the wiring diagrams as a guide, check all related splices and connectors for signs of water intrusion, corrosion, pushed out or bent terminals, and correct pin tension.
4. Wiggle the wiring and connectors while checking for shorted and open circuits.
  Were there any problems found?
  
  Yes
  - Repair as necessary.
  - Perform the HVAC VERIFICATION TEST. Refer to STANDARD PROCEDURE .
  No
  - Test complete.