B11EC

B11EC-12-CABIN TEMPERATURE FAN MOTOR CONTROL - CIRCUIT SHORT TO BATTERY





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 receives the resistance value over a two wire circuit that is used to calculate the temperature and make any adjustments to maintain the optimum passenger compartment comfort. The In-Car Temperature Sensor cannot be adjusted or repaired and must be replaced if inoperative or damaged.

- When Monitored:
With the ignition on.

- Set Condition:
The A/C Heater Control detects on the In-Car Temperature Sensor signal circuit an input voltage greater than 4.9 volts for a continuous period of two seconds or more. This DTC has a de-maturing time of 20 ms. If the DTCs status changes from active to stored, the DTC will stay in memory 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 7

2. CHECK IF THE IN-CAR TEMPERATURE SENSOR IS PROPERLY CONNECTED
1. Turn the ignition off to the lock position.
2. Check the connector to the In-Car Temperature Sensor for proper connection and the terminals for damage or corrosion.

Is the In-Car Temperature Sensor connector properly connected and terminals undamaged or corroded?

Yes

- Go To 3

No

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

3. CHECK THE (C36) IN-CAR TEMPERATURE SENSOR SIGNAL CIRCUIT FOR A SHORT TO VOLTAGE




1. Turn the ignition off to the lock position.
2. Disconnect the A/C Heater Control C1 harness connector.
3. Disconnect the In-Car Temperature Sensor harness connector.
4. Ignition on, engine not running.
5. Measure the voltage of the (C36) In-Car Temperature Sensor Signal circuit.

Is there any voltage present?

Yes

- Repair the In-Car Temperature Sensor Signal circuit for a short to voltage.
- Perform the HVAC VERIFICATION TEST. HVAC Verification Test.

No

- Go To 4

4. CHECK THE (C36) IN-CAR TEMPERATURE SENSOR SIGNAL CIRCUIT FOR AN OPEN




1. Turn the ignition off to the lock position.
2. Measure the resistance of the (C36) In-Car Temperature Sensor Signal circuit between the A/C Heater Control C1 harness connector and the In-Car Temperature Sensor harness connector.

Is the resistance above 1.0 Ohm?

Yes

- Repair the In-Car Temperature Sensor Signal circuit for an open.
- Perform the HVAC VERIFICATION TEST. HVAC Verification Test.

No

- Go To 5

5. CHECK THE (C121) SENSOR GROUND CIRCUIT FOR AN OPEN




1. Measure the resistance of the (C121) Sensor Ground circuit between the A/C Heater Control C1 harness connector and the In-Car Temperature Sensor harness connector.

Is the resistance above 1.0 Ohm?

Yes

- Repair the (C121) Sensor Ground circuit for an open.
- Perform the HVAC VERIFICATION TEST. HVAC Verification Test.

No

- Go To 6

6. CHECK THE IN-CAR TEMPERATURE SENSOR




1. Remove the In-Car Temperature Sensor. In-Car Temperature Sensor - Removal.
2. Measure the resistance of the In-Car Temperature Sensor and compare the resistance to the In-Car Temperature Sensor Resistance Chart. Testing and Inspection.

Is the In-Car Temperature Sensor within the specified limits of In-Car Temperature Sensor Resistance Chart?

Yes

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

No

- Replace the In-Car Temperature Sensor. In-Car Temperature Sensor - Installation
- Perform the HVAC VERIFICATION TEST. HVAC Verification Test.

7. 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.