Pinpoint Test C: DTC B1249
Climate Control System
Pinpoint Tests
Pinpoint Test C: DTC B1249
Refer to Wiring Diagram Set 55, Automatic Climate Control System for schematic and connector information. Diagrams By Number
Normal Operation
Under normal operation, to rotate the temperature blend door actuator, the HVAC module supplies voltage and ground to the temperature blend door actuators through the door actuator motor circuits. To reverse the temperature blend door actuator rotation, the HVAC module reverses the voltage and ground circuits.
The temperature blend door actuator feedback resistors are supplied a ground from the HVAC module by the temperature blend door actuator return circuits and a 5-volt reference voltage on the temperature blend door actuator reference circuits. The HVAC module reads the voltage on the temperature blend door actuator feedback circuits to determine the temperature blend door actuator position by the position of the actuator feedback resistor wiper arm.
During an actuator calibration cycle, the HVAC module drives the temperature blend door until the door reaches both internal stops in the HVAC case. If the temperature blend door is temporarily obstructed or binding during a calibration cycle, the HVAC module may interpret this as the actual end of travel for the door. When this condition occurs and the HVAC module commands the actuator to its end of travel, the airflow may not be the expected temperature.
- DTC B1249 (Blend Door Failure) - The module senses no change in actuator feedback voltage when the actuator motor has been energized.
This pinpoint test is intended to diagnose the following:
- Wiring, terminals or connectors
- Temperature blend door actuator
- HVAC module
- Stuck or bound linkage or door
PINPOINT TEST C: DTC B1249
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C1 CHECK THE FEEDBACK POTENTIOMETER TOTAL RESISTANCE
- Ignition OFF.
- Disconnect: HVAC Module C228A.
- Disconnect: HVAC Module C228B.
- Measure the resistance between HVAC module C228A-6, circuit 600 (DB), harness side and HVAC module C228B-9, circuit 438 (RD/WH), harness side.
- Is the resistance between 5,000 and 6,000 ohms?
Yes
GO to C2.
No
If the resistance is greater than 6,000 ohms, GO to C4.
If the resistance is less than 5,000 ohms, GO to C5.
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C2 CHECK POTENTIOMETER LOW-SIDE RESISTANCE
- Measure the resistance between HVAC module C228A-18, circuit 437 (YE/LG), harness side and HVAC module C228B-9, circuit 438 (RD/WH), harness side.
- Is the resistance between 250 and 3,000 ohms?
Yes
GO to C3.
No
If the resistance is greater than 3,000 ohms, GO to C6.
If the resistance is less than 250 ohms, GO to C7.
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C3 CHECK POTENTIOMETER HIGH-SIDE RESISTANCE
- Measure the resistance between HVAC module C228A-6, circuit 600 (DB), harness side and HVAC module C228A-18, circuit 437 (YE/LG), harness side.
- Is the resistance between 3,000 and 6,000 ohms?
Yes
GO to C9.
No
If the resistance is greater than 6,000 ohms, GO to C14. If the resistance is less than 3,000 ohms, GO to C8.
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C4 CHECK CIRCUITS 600 (DB) AND 438 (RD/WH) FOR AN OPEN
NOTE: Access to the connector in the following step is difficult. Before performing this step, visually inspect the actuator and its harness for obvious damage. If no damage is evident, proceed with the test.
- Disconnect: Temperature Blend Door Actuator C289.
- Measure the resistance between HVAC module C228A-6, circuit 600 (DB), harness side and temperature blend door actuator C289-6, circuit 600 (DB), harness side.
- Measure the resistance between HVAC module C228B-9, circuit 438 (RD/WH), harness side and temperature blend door actuator C289-5, circuit 438 (RD/WH), harness side.
- Are the resistances less than 5 ohms?
Yes
GO to C14.
No
REPAIR the affected circuit for an open. CLEAR the DTCs. REPEAT the self-test. TEST the system for normal operation.
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C5 CHECK CIRCUITS 438 (RD/WH) AND 600 (DB) FOR A SHORT TOGETHER
NOTE: Access to the connector in the following step is difficult. Before performing this step, visually inspect the actuator and its harness for obvious damage. If no damage is evident, proceed with the test.
- Disconnect: Temperature Blend Door Actuator C289.
- Measure the resistance between HVAC module C228B-9, circuit 438 (RD/WH), harness side and HVAC module C228A-6, circuit 600 (DB), harness side.
- Is the resistance greater than 10,000 ohms?
Yes
GO to C14.
No
REPAIR circuits 438 (RD/WH) for a short to circuit 600 (DB). CLEAR the DTCs. REPEAT the self-test. TEST the system for normal operation.
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C6 CHECK CIRCUIT 437 (YE/LG) FOR AN OPEN
NOTE: Access to the connector in the following step is difficult. Before performing this step, visually inspect the actuator and its harness for obvious damage. If no damage is evident, proceed with the test.
- Disconnect: Temperature Blend Door Actuator C289.
- Measure the resistance between HVAC module C228A-18, circuit 437 (YE/LG), harness side and temperature blend door actuator C289-1, circuit 437 (YE/LG), harness side.
- Is the resistance less than 5 ohms?
Yes
GO to C14.
No
REPAIR circuit 437 (YE/LG) for an open. CLEAR the DTCs. REPEAT the self-test. TEST the system for normal operation.
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C7 CHECK CIRCUITS 438 (RD/WH) AND 437 (YE/LG) FOR A SHORT TOGETHER
NOTE: Access to the connector in the following step is difficult. Before performing this step, visually inspect the actuator and its harness for obvious damage. If no damage is evident, proceed with the test.
- Disconnect: Temperature Blend Door Actuator C289.
- Measure the resistance between HVAC module C228B-9, circuit 438 (RD/WH), harness side and HVAC module C228A-18, circuit 437 (YE/LG), harness side.
- Is the resistance greater than 10,000 ohms?
Yes
GO to C14.
No
REPAIR circuits 438 (RD/WH) and 437 (YE/LG) for a short together. CLEAR the DTCs. REPEAT the self-test. TEST the system for normal operation.
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C8 CHECK CIRCUIT 437 (YE/LG) FOR A SHORT TO CIRCUIT 436 (RD/LG) OR 600 (DB)
NOTE: Access to the connector in the following step is difficult. Before performing this step, visually inspect the actuator and its harness for obvious damage. If no damage is evident, proceed with the test.
- Disconnect: Temperature Blend Door Actuator C289.
- Measure the resistance between HVAC module C228A-6, circuit 600 (DB), harness side and HVAC module C228A-18, circuit 437 (YE/LG), harness side.
- Is the resistance greater than 10,000 ohms?
Yes
GO to C14.
No
REPAIR circuits 437 (YE/LG) for a short to circuit 600 (DB). CLEAR the DTCs. REPEAT the self-test. TEST the system for normal operation.
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C9 CHECK CIRCUITS 600 (DB), 437 (YE/LG) AND 438 (RD/WH) FOR A SHORT TO VOLTAGE
- Ignition ON.
- Measure the voltage between ground and:
- HVAC module C228A-6, circuit 600 (DB), harness side.
- HVAC module C228A-18, circuit 437 (YE/LG), harness side.
- HVAC module C228B-9, circuit 438 (RD/WH), harness side.
- Is any voltage present?
Yes
REPAIR the affected circuit for a short to voltage. CLEAR the DTCs. REPEAT the self-test. TEST the system for normal operation.
No
GO to C10.
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C10 CHECK CIRCUITS 600 (DB) AND 437 (YE/LG) FOR A SHORT TO GROUND
- Measure the resistance between ground and:
- HVAC module C228A-6, circuit 600 (DB), harness side.
- HVAC module C228A-18, circuit 437 (YE/LG), harness side.
- Are the resistances greater than 10,000 ohms?
Yes
INSPECT for a broken door or linkage. If no condition is found, GO to C11.
No
REPAIR circuit 600 (DB) or 437 (YE/LG) for a short to ground. CLEAR the DTCs. REPEAT the self-test. TEST the system for normal operation.
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C11 CHECK THE BLEND DOOR ACTUATOR OPERATION
NOTE: If a jumper fuse opens while carrying out this test step, repair the circuit(s) for a short.
- With the fused jumper connections made as directed below, measure the resistance between HVAC module C228A-18, circuit 437 (YE/LG), harness side and HVAC module C228B-9, circuit 438 (RD/WH), harness side.
- Connect a fused jumper wire between HVAC module C228B-26, circuit 246 (VT), harness side and HVAC module C228A-2, circuit 1566 (RD/YE), harness side. Connect a second fused jumper wire between HVAC module C228B-13, circuit 245 (BN/LG), harness side and HVAC module C228A-3, circuit 57 (BK), harness side.
- Connect a fused jumper wire between HVAC module C228B-13, circuit 245 (BN/LG), harness side and HVAC module C228A-2, circuit 1566 (RD/YE), harness side. Connect a second fused jumper wire between HVAC module C228B-26, circuit 246 (VT), harness side and HVAC module C228A-3, circuit 57 (BK), harness side.
- Does the resistance smoothly increase and/or decrease when the jumpers are connected?
Yes
INSPECT for binding or broken door and linkage. If no condition is found, GO to C15.
No
GO to C12.
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C12 CHECK THE ACTUATOR MOTOR DRIVE CIRCUITS
- Ignition OFF.
- Measure the resistance between HVAC module C228B-13, circuit 245 (BN/LG), harness side and HVAC module C228B-26, circuit 246 (VT), harness side.
- Is the resistance approximately 20-80 ohms?
Yes
INSPECT for binding or broken door and linkage. If no condition is found, INSTALL a new door actuator. CLEAR the DTCs. REPEAT the self-test. TEST the system for normal operation.
No
GO to C13.
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C13 CHECK CIRCUITS 246 (VT) AND 245 (BN/LG) FOR AN OPEN
- Disconnect: Temperature Blend Door Actuator C289.
- Measure the resistance between HVAC module C228B-26, circuit 246 (VT), harness side and temperature blend door actuator C289-7, circuit 246 (VT), harness side.
- Measure the resistance between HVAC module C228B-13, circuit 245 (BN/LG), harness side and temperature blend door actuator C289-8, circuit 245 (BN/LG), harness side.
- Are the resistances less than 5 ohms?
Yes
GO to C14.
No
REPAIR the affected circuit for an open. CLEAR the DTCs. REPEAT the self-test. TEST the system for normal operation.
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C14 CHECK THE ACTUATOR CONNECTION
- Disconnect the actuator connector.
- Check for:
- corrosion.
- pushed-out terminals.
- damaged terminals.
- Connect and correctly seat the actuator connector.
- Clear the DTCs.
- Operate the system and verify the concern is still present.
- Is the concern still present?
Yes
INSTALL a new temperature blend door actuator. If a new actuator is installed, CONNECT the actuator electrical connectors before the HVAC module connectors. This will allow the new actuator to be calibrated when the HVAC module is reconnected. CLEAR the DTCs. REPEAT the self-test. TEST the system for normal operation.
No
The system is operating correctly at this time. The concern may have been caused by a loose or corroded connector. CLEAR the DTCs. TEST the system for normal operation.
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C15 MODULE ACTUATOR POSITION CALIBRATION
NOTE: The purpose of the module actuator position calibration is to allow the HVAC module to reinitialize and calibrate the actuator stop points. To carry out the calibration, follow the steps below.
- Ignition OFF.
- Inspect the module connectors for:
- corrosion.
- pushed-out terminals.
- damaged terminals.
- Connect and correctly seat all the HVAC module connectors.
- Ignition ON.
- Clear the DTCs.
- Select any position except OFF.
- NOTE: The HVAC module will now initialize and calibrate the actuators. Calibration of the actuators will take approximately 30 seconds.
- Operate the system and verify the concern is still present.
- Is the concern still present?
Yes
INSTALL a new HVAC module. REFER to Climate Control Heating Ventilation Air Conditioning (HVAC) Module. TEST the system for normal operation.
No
The system is now operating correctly at this time. The concern may have been caused by a foreign object in the HVAC case or temporary binding that restricted actuator door travel. CHECK any actuator external linkage. If condition recurs, INSPECT actuator linkage and door for binding and CHECK HVAC case for foreign objects.
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