B1204
DTC B1204 AIR MIX POTENTIOMETER OPEN (LOW) - PASSENGER'SComponent Location:
GENERAL DESCRIPTION
Temperature control actuator located at heater unit. It contains temp motor that changes temp door position and potentiometer that monitors position of temp door. Temperature control actuator regulates the temperature by the procedure as follows. Signal from control unit adjusts position of temp door by operating temp motor and then temperature will be regulated by the hot/cold air ratio decided by position of temp door, In operation, potentiometer delivers temp door position transformed into voltage value to A/C ECU.
DTC DESCRIPTION
The ECM sets DTC B1204 if there is an open circuit or poor connection in the passenger air mix actuator signal harness.
DTC Detecting Condition:
Signal Waveform And Data:
Schematic Diagram:
MONITOR DTC STATUS
1. Connect scantool to Data Link Connector (DLC).
2. Warm up the engine to normal operating temperature.
3. Monitor DTC (Diagnostics Trouble Code) on the scantool.
4. Is the same DTC displayed again?
YES - Go to "Inspection/Repair " procedure
NO - Fault is intermittent caused by poor contact In the sensor's and/or A/C-ECM connector or was repaired and A/C-ECM memory was not cleared. Thoroughly check connectors for looseness, poor connection, bending, corrosion, contamination, deterioration, or damage. Repair or replace as necessary and go to "Verification of vehicle Repair" procedure.
W/HARNESS INSPECTION
1. Many malfunctions in the electrical system are caused by poor harness and terminals. Faults can also be caused by interference from other electrical systems, and mechanical or chemical damage.
2. Thoroughly check connectors for looseness, poor connection, bending, corrosion, contamination, deterioration,or damage.
3. Has a problem been found?
YES - Repair as necessary and go to "Verification of Vehicle Repair" procedure
NO - Go to "Signal circuit Open Inspection" procedure.
SIGNAL CIRCUIT OPEN INSPECTION
1. Ignition "OFF"
2. A/C-ECU, passenger air mix actuator : Disconnect.
3. Measure resistance between Signal (F/B) terminal of passenger air mix actuator harness connector and Signal (F/B) terminal of A/C-ECU harness connector.
Specification : 1 ohm below
4. Is "resistance" display near the specified value?
YES - Go to "Sensor ground circuit Open Inspection " procedure.
NO
- Check for open in harness.
- Repair as necessary and then go to "Verification of Vehicle Repair" procedure.
SIGNAL GROUND CIRCUIT OPEN INSPECTION
1. Ignition "OFF"
2. A/C-ECU : Connect, passenger air mix actuator : Disconnect.
3. Measure resistance between Signal(F/B) terminal of passenger air mix actuator harness connector and and chassis ground.
Specification : Infinity
4. Is "resistance" display near the specified value?
YES - Go to "Power circuit Open Inspection" procedure.
NO
- Check for short to ground in control harness.
- Repair as necessary and then go to "Verification of Vehicle Repair" procedure.
POWER CIRCUIT GROUND SHORT INSPECTION
1. Ignition "OFF"
2. A/C-ECU, passenger air mix actuator : Disconnect.
3. Measure resistance between Sensor REF (5 V) terminal of passenger air mix actuator harness connector and Sensor REF (5 V) terminal of A/C-ECU harness connector.
Specification : 1 ohm below
4. Is "resistance" display near the specified value?
YES - Go to "Power circuit Inspection" procedure.
NO
- Check for open in harness.
- Repair as necessary and then go to "Verification of Vehicle Repair" procedure.
POWER CIRCUIT INSPECTION
1. Ignition "OFF"
2. A/C-ECU : Connect. passenger air mix actuator. Disconnect
3. Ignition "ON" (ENGINE "OFF").
4. Measure voltage between Sensor REF (5 V) terminal of passenger air mix actuator harness connector and and chassis ground.
Specification: approx. 5 V
5. Is "voltage" display near the specified value?
YES - Go to "Sensor ground circuit Open Inspection" procedure.
NO
- Check for open in harness.
- Repair as necessary and then go to "Verification of Vehicle Repair" procedure.
SENSOR GROUND CIRCUIT OPEN INSPECTION
1. Ignition "OFF"
2. A/C-ECU, passenger air mix actuator : Disconnect
3. Measure resistance between Sensor ground (-) terminal of passenger air mix actuator harness connector and Sensor ground (-) terminal of A/C-ECU harness connector
Specification: 1 ohm below
4. Is "resistance" display near the specified value?
YES - Go to " Component inspection " procedure
NO
- Check for open in harness.
- Repair as necessary and then go to "Verification of Vehicle Repair" procedure
COMPONENT INSPECTION
CHECK PASSENGER AIR MIX ACTUATOR
1. Ignition "OFF".
2. A/C-ECU, passenger air mix actuator : Disconnect.
3. Connect (+) terminal of battery to WARM(+) of passenger air mix actuator and (-) terminal to COOL (-). (Component side)
4. Verify that the temperature actuator operates to the cool position
5. Verify that the temperature actuator operates to the warm position with reverse connecting.(WARM (+) and COOL (-)). (Component side)
Specification : Refer the specifications in fig.1
6. Is "Door position" display near the specified value?
YES - Go to "Check potentiometer" procedure.
NO - Substitute with a known-good passenger air mix actuator and check for proper operation. If the problem is corrected, replace passenger air mix actuator and then go to "Verification of Vehicle Repair" procedure.
CHECK POTENTIOMETER
1. Ignition "OFF"
2. A/C-ECU : Connect, passenger air mix actuator : Disconnect.
3. Ignition "ON" (ENGINE "OFF").
4. Measure voltage between Signal (F/B) terminal of passenger air mix actuator harness connector and and Sensor ground (-) terminal of A/C-ECU harness connector. (Component side)
Specification : Refer the specifications in fig.2
5. Is "voltage" display near the specified value?
YES - Check connectors for looseness, poor connection, bending, corrosion, contamination, deterioration, or damage. Repair or replace as necessary and then go to "Verification of Vehicle Repair" procedure.
NO - Substitute with a known-good passenger air mix actuator and check for proper operation. If the problem is corrected, replace passenger air mix actuator and then go to "Verification of Vehicle Repair" procedure.
VERIFICATION OF VEHICLE REPAIR
After a repair, it is essential to verifying that the fault has been corrected.
1. Connect scan tool and select "Diagnostic Trouble Codes (DTCs)" mode.
2. Using scantool, Clear DTC.
3. Operate the vehicle within DTC Enable conditions in General Information.
4. Are any DTCs present?
YES - Go to the applicable troubleshooting procedure
NO - System is performing to specification at this time.