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Cooldown Test Too Cold to Start

COOLDOWN TEST TOO COLD TO START

Cooldown Test Too Cold To Start:





WHEN MONITORED
When executing the Cooldown Test.

SET CONDITION
This message will display if the A/C Heater Control senses that the evaporator temperature is below 12.7° C (55° F) when executing the Cooldown Test.

POSSIBLE CAUSES
- Evaporator temperature below 12.7° C (55° F) at start of test
- Faults present in the HVAC system
- Faults present in the powertrain system
- High resistance on (C121) sensor ground circuit
- High resistance on (C21) evaporator temperature sensor signal circuit
- Evaporator temperature sensor
- A/C heater control

Diagnostic Test

1. VERIFY IF THE FAULT SET DUE TO EVAPORATOR TEMPERATURE BEING BELOW 12.7° C (55° F)

CAUTION: The work area ambient temperature must be above 21.1° C (70° F) and the evaporator temperature must be above 12.7° C (55° F) in order to test A/C system performance.

Start the engine.
Make sure that Mode Select control is in the panel position and the A/C mode switch is turned off (status indicator not illuminated/compressor not running).
Turn the blower control on high speed.
Allow the blower to run for 5 minutes to ensure that the sensor temperature is above 12.7° C (55° F).
With the DRBIII(R) in HVAC, select System Tests and then select AC Cooldown test.
Allow one minute for the test to complete.

Q: Does the DRBIII(R) display: Cooldown Test Too Cold To Start?

YES: Go To 2
NO: Perform additional testing as necessary. Perform BODY VERIFICATION TEST - VER 1. Body Verification Test

2. CHECK FOR DTCS IN THE A/C HEATER CONTROL
Turn the engine off (ignition on).
With the DRBIII(R), read HVAC DTCs.

Q: Does the DRBIII(R) display any DTCs?

YES: Diagnose and repair the DTC(s). When the repair is complete, erase the DTCs, cycle the ignition switch, start the engine, set the blower control to high speed, and then re-run the Cooldown Test. Perform BODY VERIFICATION TEST - VER 1. Body Verification Test
NO: Go To 3

3. CHECK FOR DTCS IN THE PCM OR ECM
With the DRBIII(R), read PCM or ECM DTCs.

Q: Does the DRBIII(R) display any DTCs?

YES: (Gasoline Engines)
Diagnose and repair the DTC(s).When the repair is complete, erase the DTCs, cycle the ignition switch, start the engine, set the blower control to high speed, and then re-run the Cooldown Test. Perform BODY VERIFICATION TEST - VER 1. Body Verification Test
YES: (Diesel Engines)
Diagnose and repair the DTC(s). When the repair is complete, erase the DTCs, cycle the ignition switch, start the engine, set the blower control to high speed, and then re-run the Cooldown Test. Perform BODY VERIFICATION TEST - VER 1. Body Verification Test
NO: Go To 4

4. CHECK (C21) EVAPORATOR TEMPERATURE SENSOR SIGNAL CIRCUIT VOLTAGE WITH THE SENSOR DISCONNECTED




Turn the ignition off.
Disconnect the Evaporator Temperature Sensor harness connector.
Turn the ignition on.
With the DRBIII(R) in Sensor Display, read the Evaporator Temperature Sensor voltage.

Q: Is the voltage above 4.9 volts?

YES: Go To 5
NO: Go To 6

5. CHECK (C21) EVAPORATOR TEMPERATURE SENSOR SIGNAL CIRCUIT & (C121) SENSOR GROUND CIRCUIT FUNCTION




Turn the ignition off.
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.
Turn the ignition on.
With the DRBIII(R) in Sensor Display, read the Evaporator Temperature Sensor voltage.

Q: Is the voltage below 0.10 volts?

YES: Replace the Evaporator Temperature Sensor. When the repair is complete, start the engine, set the blower control to high speed, and then re-run the Cooldown Test. Perform BODY VERIFICATION TEST - VER 1. Body Verification Test
NO: Go To 6

6. CHECK THE (C121) SENSOR GROUND CIRCUIT FOR HIGH RESISTANCE

NOTE: Ensure that the voltmeter leads are connected for positive polarity and that they meet the terminals in the connector. Also ensure that there is a good terminal to wire connection.




Turn the ignition off.
Remove the jumper wire from the Evaporator Temperature Sensor harness connector.
Reconnect the Evaporator Temperature Sensor harness connector.
Back probe the (C121) Sensor Ground circuit between the Evaporator Temperature Sensor harness connector and the A/C Heater Control C1 harness connector.
Turn the ignition on.

Q: Is the voltage below 0.10 volts?

YES: Go To 7
NO: Repair the (C121) Sensor Ground circuit for high resistance. When the repair is complete, start the engine, set the blower control to high speed, and then re-run the Cooldown Test. Perform BODY VERIFICATION TEST - VER 1. Body Verification Test

7. CHECK THE (C21) EVAPORATOR TEMPERATURE SENSOR SIGNAL CIRCUIT FOR HIGH RESISTANCE

NOTE: Ensure that the voltmeter leads are connected for positive polarity and that they meet the terminals in the connector. Also ensure that there is a good terminal to wire connection.




Turn the ignition off.
Back probe the (C21) Evaporator Temperature Sensor Signal circuit between the Evaporator Temperature Sensor harness connector and the A/C Heater Control C1 harness connector.
Turn the ignition on.

Q: Is the voltage below 0.10 volts?

YES: Replace the A/C Heater Control. Perform BODY VERIFICATION TEST - VER 1. Body Verification Test
NO: Repair the (C21) Evaporator Temperature Sensor Signal circuit for high resistance. When the repair is complete, start the engine, set the blower control to high speed, and then re-run the Cooldown Test. Perform BODY VERIFICATION TEST - VER 1. Body Verification Test
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