B1918

B1918-49-CABIN TEMPERATURE SENSOR MICRO FAN - INTERNAL ELECTRONIC FAILURE

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

Theory of Operation

The HVAC A/C Heater Control uses a variety of sensors to adjust HVAC operation to obtain optimal performance. These sensors are continuously monitored by the A/C Heater Control to assure that they are in range. An active Diagnostic trouble Code (DTC) indicates that a sensor is out of range. A stored DTC indicates that the sensor was out of range but is currently within range.

The In-Car Temperature Sensor uses a temperature thermistor which changes in its resistive value with differences in air temperature of the interior cabin. Air is drawn from the passenger compartment by an aspirator (small fan driven by a 12-volt electric motor) which circulates air over the temperature thermistor. The A/C Heater Control uses the resistance value to calculate the temperature and make any adjustments to maintain the optimum passenger compartment comfort.

- When Monitored:
With the ignition on.

- Set Condition:
When the A/C Heater Control detect a malfunction in the In-Car Temperature Sensor Aspirator motor. If the A/C Heater Control detects a valid aspirator motor signal, 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.

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

Is this DTC active?

Yes

- Go To 2

No

- Go To 3

2. CHECK THE IN-CAR TEMPERATURE SENSOR ASPIRATOR MOTOR
1. Turn the ignition off.
2. Replace the In-Car Temperature Sensor Aspirator Motor. A/C And Heater Control - Removal.
3. Ignition on, engine not running.
4. With the scan tool, erase HVAC DTCs.
5. Cycle the ignition off, then back on and check HVAC DTCs.

Does this DTC reset?

Yes

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

No

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

3. CHECK THE WIRING AND CONNECTORS
1. The conditions necessary to set the DTC are not present at this time.
2. With 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.