74–AC REQUEST OUTPUT SIGNAL TOO LOW (MTC)

For a complete wiring diagram Refer to Section 8W.

When Monitored:
With the ignition on.
Set Condition:
If the A/C Heater Control detects voltage below 1.51 volts on the (C221) A/C Switch Sense circuit.

Possible Causes

(C221) A/C SWITCH SENSE CIRCUIT SHORTED TO GROUND

(C221) A/C SWITCH SENSE CIRCUIT OPEN

INSTRUMENT CLUSTER (CCN)

A/C HEATER CONTROL

NOTE: This DTC must be active for the results of this test to be valid. Do not perform this test if this DTC is stored. Refer to HVAC System Test (MTC) for stored DTC test procedures.

Diagnostic Test

1.CHECK (C221) A/C SWITCH SENSE CIRCUIT VOLTAGE AT A/C HEATER CONTROL C1 HARNESS CONNECTOR

Is the voltage below 4.8 volts?

Yes

Go To 2

Replace the A/C Heater Control in accordance with the Service Information.
Perform BODY VERIFICATION TEST - VER 1. (Refer to 8 - ELECTRICAL/ELECTRONIC CONTROL MODULES - STANDARD PROCEDURE).

2.CHECK (C221) A/C SWITCH SENSE CIRCUIT FOR A SHORT TO GROUND

Is the resistance below 10K ohms?

Yes

Repair the (C221) A/C Switch Sense circuit for a short to ground.
Perform BODY VERIFICATION TEST - VER 1. (Refer to 8 - ELECTRICAL/ELECTRONIC CONTROL MODULES - STANDARD PROCEDURE).

Go To 3

3.CHECK (C221) A/C SWITCH SENSE CIRCUIT FOR AN OPEN

Is the resistance below 5.0 ohms?

Yes

Replace the Instrument Cluster (CCN) in accordance with the Service Information.
Perform BODY VERIFICATION TEST - VER 1. (Refer to 8 - ELECTRICAL/ELECTRONIC CONTROL MODULES - STANDARD PROCEDURE).

Repair the (C221) A/C Switch Sense circuit for an open.
Perform BODY VERIFICATION TEST - VER 1. (Refer to 8 - ELECTRICAL/ELECTRONIC CONTROL MODULES - STANDARD PROCEDURE).