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
Turn the ignition off.
Disconnect the A/C Heater Control C1 harness connector.
Turn the ignition on.
Measure the voltage of the (C221) A/C Switch Sense circuit.
Is the voltage below 4.8 volts?
Yes
- Go To 2
No
- 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
Turn the ignition off.
Disconnect the Instrument Cluster C3 harness connector.
Measure the resistance of the (C221) A/C Switch Sense circuit between ground and the A/C Heater Control C1 harness connector.
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).
No
- Go To 3
3. CHECK (C221) A/C SWITCH SENSE CIRCUIT FOR AN OPEN
Measure the resistance of the (C221) A/C Switch Sense circuit between the A/C Heater Control C1 harness connector and the Instrument Cluster C3 harness connector.
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).
No
- 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).