81-BLOWER NOT ON HIGH AT START OF COOLDOWN TEST (MTC)

For a complete wiring diagram Refer to Section 8W.

When Monitored:
When executing the Cooldown Test.
Set Condition:
If the A/C Heater Control sensed that the blower was not operating at high speed when executing the Cooldown Test.

Possible Causes

BLOWER CONTROL NOT SET TO HIGH SPEED WHEN EXECUTING THE COOLDOWN TEST

BLOWER MOTOR / RELATED CIRCUITS

(C41) BLOWER SWITCH POSITION SIGNAL CIRCUIT SHORTED TO (C121) SENSOR GROUND CIRCUIT

(C41) BLOWER SWITCH POSITION SIGNAL CIRCUIT SHORTED TO GROUND

(C41) BLOWER SWITCH POSITION SIGNAL CIRCUIT OPEN

A/C HEATER CONTROL

NOTE: This DTC will display as active if the ignition is not cycled after running the Cooldown Test. Otherwise, it will display as stored until cleared.

Diagnostic Test

1. CHECK THE BLOWER SPEED SETTING

Was the blower control set to high speed before executing the Cooldown Test?

Yes

Go To 2

Start the engine, set the blower control to high speed, and then run the Cooldown Test again.
Perform BODY VERIFICATION TEST - VER 1. (Refer to 8 - ELECTRICAL/ELECTRONIC CONTROL MODULES - STANDARD PROCEDURE).

2. CHECK THE (C41) BLOWER SWITCH POSITION SIGNAL CIRCUIT FOR A SHORT TO THE (C121) SENSOR GROUND CIRCUIT

Turn the ignition off.
Disconnect the A/C Heater Control C2 harness connector.
Measure the resistance between the (C41) Blower Switch Position Signal circuit and the (C121) Sensor Ground circuit in the A/C Heater Control C2 harness connector.

Is the resistance below 10K ohms?

Yes

Repair the (C41) Blower Switch Position Signal circuit for a short to the (C121) Sensor Ground circuit. Run the Cooldown Test again after the repair is complete.

Perform BODY VERIFICATION TEST - VER 1. (Refer to 8 - ELECTRICAL/ELECTRONIC CONTROL MODULES - STANDARD PROCEDURE).

Go To 3

3. CHECK THE (C41) BLOWER SWITCH POSITION SIGNAL CIRCUIT VOLTAGE

Reconnect the A/C Heater Control C2 harness connector.
Disconnect the A/C Heater Control C3 harness connector.
Turn the ignition on.
Measure the voltage of the (C41) Blower Switch Position Signal circuit.

Is the voltage above 4.8 volts?

Yes

Check the blower motor and related circuits for the cause of blower operation problems and repair as necessary. Run the Cooldown Test again after the repair is complete.

Perform BODY VERIFICATION TEST - VER 1. (Refer to 8 - ELECTRICAL/ELECTRONIC CONTROL MODULES - STANDARD PROCEDURE).

Go To 4

4. CHECK THE (C41) BLOWER SWITCH POSITION SIGNAL CIRCUIT FOR A SHORT TO GROUND

Turn the ignition off.
Disconnect the A/C Heater Control C2 harness connector.
Measure the resistance of the (C41) Blower Switch Position Signal circuit between ground and the A/C Heater Control C3 harness connector.

Is the resistance below 10K ohms?

Yes

Repair the (C41) Blower Switch Position Signal circuit for a short to ground. Run the Cooldown Test again after the repair is complete.

Perform BODY VERIFICATION TEST - VER 1. (Refer to 8 - ELECTRICAL/ELECTRONIC CONTROL MODULES - STANDARD PROCEDURE).

Go To 5

5. CHECK (C41) BLOWER SWITCH POSITION SIGNAL CIRCUIT FOR AN OPEN

Measure the resistance of the (C41) Blower Switch Position Signal circuit between the A/C Heater Control C2 harness connector and the A/C Heater Control C3 harness connector.

Is the resistance below 5.0 ohms?

Yes

Replace the A/C Heater Control in accordance with the Service Information. Run the Cooldown Test again after the repair is complete.

Perform BODY VERIFICATION TEST - VER 1. (Refer to 8 - ELECTRICAL/ELECTRONIC CONTROL MODULES - STANDARD PROCEDURE).

Repair the (C41) Blower Switch Position Signal circuit for an open. Run the Cooldown Test again after the repair is complete.
Perform BODY VERIFICATION TEST - VER 1. (Refer to 8 - ELECTRICAL/ELECTRONIC CONTROL MODULES - STANDARD PROCEDURE).