Diagnostic Routine A
Diagnostic Routine A
Diagnostic Overview
The Auxiliary Blower Motor Is Inoperative
Refer to Wiring Diagram Set 52 for schematic and connector information Electrical Diagrams.
Normal Operation and Fault Conditions
The auxiliary blower motor relay coil receives a ground from the HVAC (Heating, Ventilation, and Air Conditioning) module. When the relay coil is energized, voltage is delivered from the relay to the auxiliary blower motor speed control and auxiliary blower motor. The auxiliary blower motor speed control is grounded. The HVAC (Heating, Ventilation, and Air Conditioning) module provides a PWM (Pulse Width Modulated) signal to the auxiliary blower motor speed control to control the blower speed. Ground for the motor is provided from the auxiliary blower motor speed control.
DTC Fault Trigger Conditions
Visual Inspection and Diagnostic Pre-checks
- Inspect BJB (Battery Junction Box) fuses 39 (40A) and 93 (5A)
Pinpoint Test
1. CHECK THE HVAC (Heating, Ventilation, and Air Conditioning) MODULE FOR DTCs (Diagnostic Trouble Codes)
1. Ignition ON.
2. Using a scan tool, perform a HVAC (Heating, Ventilation, and Air Conditioning) module self-test.
Are any DTCs (Diagnostic Trouble Codes) present?
2. CHECK THE AUXILIARY BLOWER MOTOR RELAY FUNCTIONALITY
1. Install a known good auxiliary blower motor relay.
Does the auxiliary blower motor function correctly?
3. CHECK THE AUXILIARY BLOWER MOTOR CONTROL CIRCUIT FOR A SHORT TO VOLTAGE
1. Ignition OFF.
2. Disconnect: Auxiliary Blower Motor Relay.
3. Disconnect: HVAC (Heating, Ventilation, and Air Conditioning) module C228B.
4. Ignition ON.
5. Measure:
Is any voltage present?
4. CHECK THE AUXILIARY BLOWER MOTOR RELAY FUNCTIONALITY
1. Install a known good auxiliary blower motor relay.
Does the auxiliary blower motor function correctly?
5. CHECK THE AUXILIARY BLOWER MOTOR RELAY COIL SUPPLY VOLTAGE
1. Ignition OFF.
2. Disconnect: Auxiliary Blower Motor Relay.
3. Ignition ON.
4. Measure:
Is the voltage greater than 11 volts?
6. CHECK THE AUXILIARY BLOWER MOTOR RELAY COIL CONTROL CIRCUIT FOR AN OPEN
1. Ignition OFF.
2. Disconnect: HVAC (Heating, Ventilation, and Air Conditioning) Module C228B.
3. Measure:
Is the resistance less than 3 ohms?
7. CHECK THE AUXILIARY BLOWER MOTOR RELAY FUNCTIONALITY
1. Install a known good auxiliary blower motor relay.
Does the auxiliary blower motor function correctly?
8. CHECK FOR VOLTAGE AT THE AUXILIARY BLOWER MOTOR RELAY SWITCH CONTACT
1. Disconnect: Auxiliary Blower Motor Relay
2. Measure:
Is the voltage greater than 11 volts?
9. CHECK VOLTAGE TO THE AUXILIARY BLOWER MOTOR WITH THE AUXILIARY BLOWER MOTOR RELAY BYPASSED
1. Ignition OFF.
2. Disconnect: Auxiliary Blower Motor.
3. Disconnect: Auxiliary Blower Motor Speed Control.
4. Connect a fused jumper:
5. Measure:
Is the voltage greater than 11 volts?
10. CHECK THE AUXILIARY BLOWER MOTOR SPEED CONTROL POWER CIRCUIT FOR VOLTAGE
1. Measure:
Is the voltage greater than 11 volts?
11. CHECK FOR AUXILIARY BLOWER MOTOR FUNCTIONALITY WITH A TEST LIGHT IN PLACE OF THE AUXILIARY BLOWER MOTOR
NOTICE: This step uses a test light to simulate normal circuit loads. Use only the test light recommended in the Special Tools table at the beginning or equivalent. To avoid connector terminal damage, use the Flex Probe Kit for the test light probe connection to the vehicle. Do not use the test light probe directly on any connector.
1. Connect:
2. Ignition ON.
3. Select panel mode with the auxiliary blower motor on high.
Does the test lamp illuminate?
12. CHECK THE AUXILIARY BLOWER MOTOR GROUND CIRCUIT FOR AN OPEN
1. Ignition OFF.
2. Disconnect: Auxiliary Blower Motor Speed Control.
3. Measure:
Is the resistance less than 3 ohms?
13. CHECK THE AUXILIARY BLOWER MOTOR SPEED CONTROL GROUND CIRCUIT FOR AN OPEN
1. Measure:
Is the resistance less than 3 ohms?
14. CHECK THE AUXILIARY BLOWER MOTOR SPEED CONTROL COMMAND CIRCUIT FOR A SHORT TO GROUND
1. Disconnect: HVAC (Heating, Ventilation, and Air Conditioning) Module C228B.
2. Measure:
Is the resistance greater than 10,000 ohms?
15. CHECK THE AUXILIARY BLOWER MOTOR SPEED CONTROL COMMAND CIRCUIT FOR AN OPEN
1. Measure:
Is the resistance less than 3 ohms?
16. CHECK FOR CORRECT HVAC (Heating, Ventilation, and Air Conditioning) MODULE OPERATION
1. Ignition OFF.
2. Disconnect and inspect all 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. Reconnect all disconnected connectors. Make sure they seat and latch correctly.
6. Operate the system and determine if the concern is still present.
Is the concern still present?
