Evaporator Temperature Sensor Circuit Open (MTC)

EVAPORATOR TEMPERATURE SENSOR CIRCUIT OPEN (MTC)





For a complete wiring diagram Consult Diagrams/Electrical

- When Monitored:
With the ignition on and the IOD fuse installed.

- Set Condition:
If the A/C Heater Control detects abnormally high voltage on the (C21) Evaporator Temperature Sensor Signal circuit.





Diagnostic Test

1. CHECK FOR HVAC DTCs
Turn the ignition on.
With the scan tool, read HVAC DTCs.
Does the scan tool display any DTCs?

Yes

- Diagnose and Repair the DTC(s).
- Run the Cooldown Test after the repair is complete.
- Perform BODY VERIFICATION TEST - VER 1. Body Verification Test.

No

- Go To 2

2. CHECK (C21) EVAPORATOR TEMPERATURE SENSOR SIGNAL CIRCUIT FOR A SHORT TO VOLTAGE




Turn the ignition off.
Disconnect the A/C Heater Control C1 harness connector.
Turn the ignition on.
Measure the voltage of the (C21) Evaporator Temperature Sensor Signal circuit.
Is the voltage above 0.2 volts?

Yes

- Repair the (C21) Evaporator Temperature Sensor Signal circuit for a short to voltage.
- Perform BODY VERIFICATION TEST - VER 1. Body Verification Test.

No

- Go To 3

3. CHECK (C21) EVAPORATOR TEMPERATURE SENSOR SIGNAL CIRCUIT, (C121) SENSOR GROUND CIRCUIT, & EVAPORATOR TEMPERATURE SENSOR




Turn the ignition off.
Measure the resistance between the (C21) Evaporator Temperature Sensor Signal circuit and the (C121) Sensor Ground circuit. The approximate circuit resistance should be:
1,468 ohms @ 40°C (104°F).
1,800 ohms @ 35°C (95°F).
2,221 ohms @ 30°C (86°F).
2,757 ohms @ 25°C (77°F).
3,443 ohms @ 20°C (68°F).
4,330 ohms @ 15°C (59°F).
5,485 ohms @ 10°C (50°F).
7,354 ohms @ 4°C (39°F).
8,130 ohms @ 2°C (36°F).
Is the resistance within the specifications?

Yes

- Replace the A/C Heater Control.
- Perform BODY VERIFICATION TEST - VER 1. Body Verification Test.

No

- Go To 4

4. CHECK (C21) EVAPORATOR TEMPERATURE SENSOR SIGNAL CIRCUIT FOR AN OPEN




Disconnect the in-line C202 harness connector.
Measure the resistance of the (C21) Evaporator Temperature Sensor Signal circuit between the A/C Heater Control C1 harness connector and the in-line C202 harness connector (IP Side).
Does the ohm meter read open circuit?

Yes

- Repair the (C21) Evaporator Temperature Sensor Signal for an open.
- Perform BODY VERIFICATION TEST - VER 1. Body Verification Test.

No

- Go To 5

5. CHECK (C121) SENSOR GROUND CIRCUIT FOR AN OPEN




Measure the resistance of the (C121) Sensor Ground circuit between the A/C Heater Control C1 harness connector and the in-line C202 harness connector (IP Side).
Does the ohm meter read open circuit?

Yes

- Repair the (C121) Sensor Ground circuit for an open.
- Perform BODY VERIFICATION TEST - VER 1. Body Verification Test.

No

- Check the wiring harness between the in-line C202 harness connector (HVAC side) and the Evaporator Temperature Sensor for an open. If open, repair as necessary. Otherwise, replace the Evaporator Temperature Sensor.
- Perform BODY VERIFICATION TEST - VER 1. Body Verification Test.