Diagnostic Routine J

Diagnostic Routine J

Diagnostic Overview

The Heating Ventilation Air Conditioning (HVAC) Module Does Not Respond To The Scan Tool

Refer to Wiring Diagram Set 13 for schematic and connector information Electrical Diagrams.

Refer to Wiring Diagram Set 55 for schematic and connector information Electrical Diagrams.

Normal Operation and Fault Conditions

The HVAC (Heating, Ventilation, and Air Conditioning) module communicates with the scan tool through the MS-CAN (Medium Speed Controller Area Network).

Visual Inspection and Diagnostic Pre-checks

Verify BCM (Body Control Module) fuse 71 (10A) is OK.

Pinpoint Test

1. CHECK THE HVAC (Heating, Ventilation, and Air Conditioning) MODULE VOLTAGE SUPPLY CIRCUIT FOR AN OPEN

1. Disconnect: HVAC (Heating, Ventilation, and Air Conditioning) Module C228B.

2. Ignition ON.

3. Measure:





Is the voltage greater than 11 volts?






2. CHECK THE HVAC (Heating, Ventilation, and Air Conditioning) MODULE GROUND CIRCUIT FOR AN OPEN

1. Ignition OFF.

2. Measure:





Is the resistance less than 3 ohms?






3. CHECK THE MS-CAN (Medium Speed Controller Area Network) CIRCUITS BETWEEN THE HVAC (Heating, Ventilation, and Air Conditioning) MODULE AND THE DLC (Data Link Connector) FOR AN OPEN

1. Measure:





Are the resistances less than 3 ohms?






4. CHECK FOR CORRECT HVAC (Heating, Ventilation, and Air Conditioning) MODULE OPERATION

1. Ignition OFF.

2. Disconnect and inspect all the HVAC (Heating, Ventilation, and Air Conditioning) 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 HVAC (Heating, Ventilation, and Air Conditioning) 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?