Diagnostic Routine R
Diagnostic Routine R
Diagnostic Overview
The Blower Motor Is Inoperative
Refer to Wiring Diagram Set 55 for schematic and connector information Electrical Diagrams.
Normal Operation and Fault Conditions
When the blower motor relay coil receives a ground from the HVAC (Heating, Ventilation, and Air Conditioning) module, the relay coil is energized and voltage is delivered to the blower motor and the blower motor speed control from the relay. Ground for the motor is provided from the blower motor speed control. Ground is provided for the blower control module. The HVAC (Heating, Ventilation, and Air Conditioning) module sends a PWM (Pulse Width Modulated) signal to the blower motor speed control to control the blower speed.
DTC Fault Trigger Conditions
Visual Inspection and Diagnostic Pre-checks
- Inspect the blower motor relay.
- Inspect BJB (Battery Junction Box) fuse 18 (40A).
- Inspect BJB (Battery Junction Box) fuse 89 (5A).
Special Tool(s)
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 BLOWER MOTOR RELAY FUNCTIONALITY
1. Install a known good blower motor relay.
Does the blower motor function correctly?
3. CHECK THE BLOWER MOTOR CONTROL CIRCUIT FOR A SHORT TO VOLTAGE
1. Ignition OFF.
2. Disconnect: Blower Motor Relay.
3. Disconnect: HVAC (Heating, Ventilation, and Air Conditioning) module C228A.
4. Ignition ON.
5. Measure:
Is any voltage present?
4. CHECK THE BLOWER MOTOR RELAY FUNCTIONALITY
1. Install a known good blower motor relay.
Does the blower motor function correctly?
5. CHECK THE BLOWER MOTOR RELAY COIL SUPPLY VOLTAGE
1. Ignition OFF.
2. Disconnect: Blower Motor Relay.
3. Ignition ON.
4. Measure:
Is the voltage greater than 11 volts?
6. CHECK THE BLOWER MOTOR RELAY COIL CONTROL CIRCUIT FOR AN OPEN
1. Ignition OFF.
2. Disconnect: HVAC (Heating, Ventilation, and Air Conditioning) Module C228A.
3. Measure:
Is the resistance less than 3 ohms?
7. CHECK THE BLOWER MOTOR OPERATION USING ACTIVE COMMANDS
1. Using a scan tool, view HVAC (Heating, Ventilation, and Air Conditioning) Module PIDs (Parameter Identifications).
2. Select PANEL mode on the HVAC (Heating, Ventilation, and Air Conditioning) controls.
3. Select the lowest blower motor setting.
4. Monitor blower motor speed while using the scan tool to operate the active command PID (Parameter Identification) BLOWRSPD, increasing and decreasing the percentage value.
Does the blower motor speed change between low and high when the active command is changed?
8. CHECK THE BLOWER MOTOR RELAY FUNCTIONALITY
1. Install a known good blower motor relay.
Does the blower motor function correctly?
9. CHECK FOR VOLTAGE AT THE BLOWER MOTOR RELAY SWITCH CONTACT
1. Disconnect: Blower Motor Relay
2. Measure:
Is the voltage greater than 11 volts?
10. CHECK VOLTAGE TO THE BLOWER MOTOR WITH THE BLOWER MOTOR RELAY BYPASSED
1. Ignition OFF.
2. Disconnect: Blower Motor.
3. Connect a fused jumper:
4. Ignition ON.
5. Measure:
Is the voltage greater than 11 volts?
11. CHECK THE BLOWER MOTOR SPEED CONTROL POWER CIRCUIT FOR VOLTAGE
1. Ignition OFF.
2. Disconnect: Blower Motor Speed Control.
3. Ignition ON.
4. Measure:
Is the voltage greater than 11 volts?
12. CHECK FOR BLOWER MOTOR FUNCTIONALITY WITH A TEST LIGHT IN PLACE OF THE 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. Ignition OFF.
2. Disconnect: Blower Motor.
3. Connect:
4. Ignition ON.
5. Select panel mode with the blower motor on high.
Does the test lamp illuminate?
13. CHECK THE BLOWER MOTOR GROUND CIRCUIT FOR AN OPEN
1. Ignition OFF.
2. Disconnect: Blower Motor Speed Control.
3. Measure:
Is the resistance less than 3 ohms?
14. CHECK THE BLOWER MOTOR SPEED CONTROL GROUND CIRCUIT FOR AN OPEN
1. Measure:
Is the resistance less than 3 ohms?
15. CHECK THE BLOWER MOTOR SPEED CONTROL COMMAND CIRCUIT FOR A SHORT TO GROUND
1. Disconnect: HVAC (Heating, Ventilation, and Air Conditioning) Module C228A.
2. Measure:
Is the resistance greater than 10,000 ohms?
16. CHECK THE BLOWER MOTOR SPEED CONTROL COMMAND CIRCUIT FOR AN OPEN
1. Measure:
Is the resistance less than 3 ohms?
17. 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. Operate the system and determine if the concern is still present.
Is the concern still present?
