Diagnostic Routine U

Diagnostic Routine U

Diagnostic Overview

B1B71:21, B1B71:22, B1B71:2F

Refer to Wiring Diagram Set 54 for schematic and connector information Electrical Diagrams.

Normal Operation and Fault Conditions

REFER to Evaporator Temperature Sensor .

DTC Fault Trigger Conditions






Pinpoint Test

1. CHECK THE BCM (Body Control Module) SENSOR OUTPUT VOLTAGE

1. Ignition ON.

2. Measure:





Is the voltage between 4.7 and 5.1 volts?






2. CHECK THE EVAPORATOR TEMPERATURE SENSOR CIRCUIT FOR AN OPEN

1. Ignition OFF.

2. Disconnect: BCM (Body Control Module) C2280C.

3. Measure:





Is the resistance less than 3 ohms?






3. CHECK THE EVAPORATOR TEMPERATURE SENSOR SIGNAL RETURN CIRCUIT FOR AN OPEN

1. Measure:





Is the resistance less than 3 ohms?






4. CHECK THE EVAPORATOR TEMPERATURE SENSOR SIGNAL RETURN CIRCUIT FOR A SHORT TO POWER

1. Measure:





Is any voltage present?






5. CHECK THE EVAPORATOR TEMPERATURE SENSOR SIGNAL AND SIGNAL RETURN CIRCUITS FOR A SHORT TOGETHER

1. Ignition OFF.

2. Disconnect: BCM (Body Control Module) C2280C.

3. Disconnect: Evaporator Discharge Temperature Sensor.

4. Measure:





Is the resistance greater than 10,000 ohms?






6. CHECK THE EVAPORATOR TEMPERATURE SENSOR SIGNAL CIRCUIT FOR A SHORT TO GROUND

1. Measure:





Is the resistance greater than 10,000 ohms?






7. CHECK FOR CORRECT BCM (Body Control Module) OPERATION

1. Ignition OFF.

2. Disconnect and inspect all the BCM (Body Control Module) connectors.

3. Repair:

- corrosion (install new connector or terminals- clean module pins)
- damaged or bent pins- install new terminals/pins
- pushed-out pins- install new pins as necessary

4. Reconnect the BCM (Body Control Module) connectors. Make sure they seat and latch correctly.

5. Operate the system and determine if the concern is still present.

Is the concern still present?