B11FC-11

B11FC-11-BLEND AIR SENSOR CIRCUIT-SHORT TO GROUND

For a complete wiring diagram, refer to the Wiring Information.





Theory of Operation

The Mixing Chamber Temperature Sensor is a variable resistor that changes in conjunction with temperature, or otherwise known as a thermistor. The Mixing Chamber Temperature Sensor is located in the HVAC housing. The A/C Heater Module monitors the Mixing Chamber temperature by monitoring the voltage change of the Mixing Chamber Temperature Sensor Signal circuit. If the monitored voltage drops below or rises above a predetermined voltage, a Diagnostic Trouble Code (DTC) will set.

- When Monitored:
With the ignition on.

- Set Condition:
The A/C Heater Module detects less than 0.09 volts on the Mixing Chamber Temperature Sensor Signal circuit for a period of two seconds or more. If the A/C Heater Module detects a valid voltage, the DTC will change from active to stored and will stay stored for 100 ignition cycles.





Always perform the HVAC Pre-Diagnostic Troubleshooting procedure before proceeding. Initial Inspection and Diagnostic Overview.

Diagnostic Test

1. CHECK IF THE DTC IS ACTIVE
1. Ignition on, engine not running.
2. Using the scan tool, read HVAC DTCs.

Is this DTC active?

Yes

- Go To 2

No

- Go To 5

2. CHECK (C128) MIXING CHAMBER TEMPERATURE SENSOR SIGNAL CIRCUIT FOR A SHORT TO GROUND
1. Turn the ignition off to the lock position.
2. Disconnect the A/C Heater Module C1 harness connector.
3. Disconnect the Mixing Chamber Temperature Sensor harness connector.
4. Measure the resistance between ground and the (C128) Mixing Chamber Temperature Sensor Signal circuit.

Is the resistance below 100k Ohms?

Yes

- Repair the (C128) Mixing Chamber Temperature Sensor Signal circuit for a short to ground.
- Perform the HVAC VERIFICATION TEST. HVAC Verification Test.

No

- Go To 3

3. CHECK (C128) MIXING CHAMBER TEMPERATURE SENSOR SIGNAL CIRCUIT FOR A SHORT TO THE (C121) SENSOR GROUND CIRCUIT
1. Measure the resistance between the (C128) Mixing Chamber Temperature Sensor Signal circuit and the (C121) Sensor Ground circuit.

Is the resistance below 100k Ohms?

Yes

- Repair the (C128) Mixing Chamber Temperature Sensor Signal circuit for a short to the (C121) Sensor Ground circuit.
- Perform the HVAC VERIFICATION TEST. HVAC Verification Test.

No

- Go To 4

4. CHECK THE MIXING CHAMBER TEMPERATURE SENSOR
1. Replace the Mixing Chamber Temperature Sensor.
2. Cycle the ignition off for 30 seconds then back on.
3. With the scan tool, read HVAC DTCs.

Does this DTC reset?

Yes

- Replace and program the A/C Heater Module. A/C And Heater Control Module - Installation.
- Perform the HVAC VERIFICATION TEST. HVAC Verification Test.

No

- Test complete.
- Perform the HVAC VERIFICATION TEST. HVAC Verification Test.

5. CHECK THE WIRING AND CONNECTORS
1. The conditions necessary to set the DTC are not present at this time.
2. Using the scan tool, check the Environmental Data to help identify the conditions in which the DTC was set.
3. Using the wiring diagrams as a guide, check all related splices and connectors for signs of water intrusion, corrosion, pushed out or bent terminals, and correct pin tension.
4. Wiggle the wiring and connectors while checking for shorted and open circuits.

Were there any problems found?

Yes

- Repair as necessary.
- Perform the HVAC VERIFICATION TEST. HVAC Verification Test.

No

- Test complete.