Rear Fan Pot Open (ATC)

REAR FAN POT OPEN (ATC)





For a complete wiring diagram Consult Diagrams/Electrical

- When Monitored:
With the ignition on.

- Set Condition:
If the Rear Fan Sense input A/D counts exceed 253 (4.9 volts).





Diagnostic Test

1. ACTIVE HVAC DTC(S) PRESENT
Turn the ignition on.
Using the scan tool, clear all HVAC DTC's.
Using the A/C Heater Control, operate the Rear Fan.
With the scan tool, check for DTCs.
Does the scan tool display this DTC as active?

Yes

- Go To2

No

- The condition that caused this symptom is currently not present. Check for an intermittent condition by inspecting the related wiring harness for chafed, pierced, pinched, and partially broken wires. Also, inspect the related connectors for broken, bent, pushed out, spread, corroded, or contaminated terminals. Repair as necessary.
- Perform the BODY VERIFICATION TEST - VER 1. Body Verification Test.

2. CHECK (C11) REAR FAN SENSE SUPPLY CIRCUIT VOLTAGE




Turn the ignition off.
Disconnect the Rear Booster Fan Rear Control Switch harness connector.
Turn the ignition on.
Measure the voltage of the (C11) Rear Fan Sense Supply circuit.
Is the voltage above 5.3 volts?

Yes

- Go To 3

No

- Go To 4

3. CHECK (C11) REAR FAN SENSE SUPPLY CIRCUIT FOR A SHORT TO VOLTAGE




Turn the ignition off.
Disconnect the A/C Heater Control harness connector.
Turn the ignition on.
Measure the voltage of the (C11) Rear Fan Sense Supply circuit.
Is the voltage above 0.2 volts?

Yes

- Repair the (C11) Rear Fan Sense Supply circuit for a short to voltage.
- Perform BODY VERIFICATION TEST - VER 1. Body Verification Test.

No

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

4. CHECK (C31) REAR FAN SENSE CIRCUIT VOLTAGE




Measure the voltage of the (C31) Rear Fan Sense circuit.
What voltage is present?

Above 5.1 Volts

- Go To 5

Below 0.25 Volts

- Go To 6

Between 0.25 & 5.1 Volts

- Go To 7

5. CHECK (C31) REAR FAN SENSE CIRCUIT FOR A SHORT TO VOLTAGE




Turn the ignition off.
Disconnect the A/C Heater Control harness connector.
Turn the ignition on.
Measure the voltage of the (C31) Rear Fan Sense circuit.
Is the voltage above 0.2 volts?

Yes

- Repair the (C31) Rear Fan Sense circuit for a short to voltage.
- Perform BODY VERIFICATION TEST - VER 1. Body Verification Test.

No

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

6. CHECK (C31) REAR FAN SENSE CIRCUIT FOR AN OPEN




Turn the ignition off.
Disconnect the A/C Heater Control harness connector.
Measure the resistance of the (C31) Rear Fan Sense circuit between the A/C Heater Control harness connector and the Rear Booster Fan Rear Control Switch harness connector.
Does the ohm meter read open circuit?

Yes

- Repair the (C31) Rear Fan Sense circuit for an open.
- Perform BODY VERIFICATION TEST - VER 1. Body Verification Test.

No

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

7. CHECK (C11) REAR FAN SENSE SUPPLY CIRCUIT FOR A SHORT TO THE (C31) REAR FAN SENSE CIRCUIT




Turn the ignition off.
Disconnect the A/C Heater Control harness connector.
Measure the resistance between the (C11) Rear Fan Sense Supply circuit and the (C31) Rear Fan Sense circuit in the A/C Heater Control harness connector.
Does the ohm meter read open circuit?

Yes

- Go To 8

No

- Repair the (C11) Rear Fan Sense Supply circuit for a short to the (C31) Rear Fan Sense circuit.
- Perform BODY VERIFICATION TEST - VER 1. Body Verification Test.

8. CHECK (C931) REAR FAN SENSE RETURN CIRCUIT FOR AN OPEN




Measure the resistance of the (C931) Rear Fan Sense Return circuit between the A/C Heater Control harness connector and the Rear Booster Fan Rear Control Switch harness connector.
Does the ohm meter read open circuit?

Yes

- Repair the (C931) Rear Fan Sense Return circuit for an open.
- Perform BODY VERIFICATION TEST - VER 1. Body Verification Test.

No

- Go To 9

9. CHECK REAR BOOSTER FAN REAR CONTROL SWITCH
Reconnect all previously disconnected components.
Turn the ignition on.
With the scan tool, check the data display for the Rear Blower with the Rear Booster Fan Rear Control in the lowest and highest settings.
Does the scan tool display approximately 32.0% in the lowest setting and 100% in the highest setting?

Yes

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

No

- Replace the Rear Booster Fan Rear Control Switch.
- Perform BODY VERIFICATION TEST - VER 1. Body Verification Test.