Part 1
DTC B1045: Air mixing damper control motor and potentiometer (activating system failure)Part 1:
Part 2:
FUNCTION
Takes in fresh air or inside air from the blower, and activates the damper on the side of the heater core to control the volume of the warm air that passes through the heater core and the cool air that does not pass through the heater core.
DETECTION LOGIC
This code is set when the air mixing damper control motor and potentiometer cannot be rotated to the preset opening angle.
PROBABLE CAUSES
- Malfunction of connector.
- Malfunction of the harness (open circuit, damage or short to ground of air mixing damper control motor and potentiometer circuit, short to ground of pressure sensor circuit, and open circuit or damage of power supply (IG2) circuit)
- Malfunction of the air mixing damper control motor and potentiometer.
- Malfunction of the A/C-ECU.
- Malfunction of the junction block.
DIAGNOSIS
Required Special Tools:
- MB991223: Harness Set
- MB992006: Extra Fine Probe
- MB991958: Scan Tool (M.U.T.-III Sub Assembly)
- MB991824: V.C.I.
- MB991827: M.U.T.-III USB Cable
- MB991910: M.U.T.-III Main Harness A
STEP 1. Using scan tool MB991958, read the diagnostic trouble code.
CAUTION: To prevent damage to scan tool MB991958, always turn the ignition switch to the "LOCK" (OFF) position before connecting or disconnecting scan tool MB991958.
Check if an A/C-ECU DTC is set.
1. Connect scan tool MB991958 to the data link connector.
2. Turn the ignition switch to the "ON" position.
3. Check if the DTC is set.
4. Turn the ignition switch to the "LOCK" (OFF) position.
Q: Is only diagnostic trouble code B1045 set?
YES
NO
NO
NO
STEP 2. Check air mixing damper control motor and potentiometer connector C-109 and A/C pressure sensor connector A-34 for loose, corroded or damaged terminals, or terminals pushed back in the connector.
Q: Are air mixing damper control motor and potentiometer
connector C-109 and A/C pressure sensor connector A-34 in good condition?
YES: Go to Step 3.
NO: Repair or replace the connector. Refer to Harness Connector Inspection.
STEP 3. Check the A/C pressure sensor operation.
1. Assemble a gauge manifold on the high pressure service valve.
2. Disconnect the A/C pressure sensor connector and connect special tool test harness MB991658 as shown in the illustration.
3. Turn ON the engine and then turn ON the air conditioner switch.
4. At this time, check to see that the voltage of A/C pressure sensor terminal No. 2 reflects the specifications of the figure.
NOTE: The allowance shall be defined as ±5%.
Q: Is the A/C pressure sensor operating properly?
YES: Go to Step 4.
NO: Replace the A/C pressure sensor.
STEP 4. Check the air mixing damper control motor and potentiometer.
CAUTION: Do not apply battery voltage when the damper is in the MAX COOL or MAX HOT position.
1. Operate the air mixing damper control motor as described in the table.
2. Measure the resistances between connector terminals 3 and 5, and between 3 and 7, while the air mixing damper control motor is running. The resistances should change gradually within the standard value.
Standard value: 1.7 (MAX HOT) - 5.0 (MAX COOL) kohms
Q: Are the air mixing damper control motor and potentiometer in good condition?
YES: Go to Step 5.
NO: Replace the air mixing damper control motor and potentiometer.
STEP 5. Check A/C-ECU connector C-15 for loose, corroded or damaged terminals, or terminals pushed back in the connector.
Q: Is A/C-ECU connector C-15 in good condition?
YES: Go to Step 6.
NO: Repair or replace the connector. Refer to Harness Connector Inspection.
STEP 6. Measure the resistance at A/C-ECU connector C-15.
1. Disconnect A/C-ECU connector C-15, and measure the resistance at the wiring harness side.
2. Measure the resistance value between terminal 12 and ground.
OK: 1.5 kohms or more
Q: Does the measured resistance value correspond with this range?
YES: Go to Step 8.
NO: Go to Step 7.
STEP 7. Check the wiring harness between A/C-ECU connector C-15 (terminal 12) and A/C pressure sensor connector A-34 (terminal 3).
NOTE: Also check intermediate connector C-24 for loose, corroded, or damaged terminals, or terminals pushed back in the connector. If intermediate connector C-24 is damaged, repair or replace the connector as described in Harness Connector Inspection.
Q: Is the wiring harness between A/C-ECU connector C-15 (terminal 12) and A/C pressure sensor connector A-34 (terminal 3) in good condition?
YES: It can be assumed that this malfunction is intermittent. Refer to How to Use Troubleshooting/Inspection Service Points - How to Cope with Intermittent Malfunctions.
NO: Repair the wiring harness.
STEP 8. Measure the resistance at A/C-ECU connector C-15.
1. Disconnect A/C-ECU connector C-15, and measure the resistance at the wiring harness side.
2. Measure the resistance value between terminal 16 and ground.
OK: 1 kohm or more
Q: Does the measured resistance value correspond with this range?
YES: Go to Step 10.
NO: Go to Step 9.
STEP 9. Check the wiring harness between A/C-ECU connector C-15 (terminal 16) and air mixing damper control motor and potentiometer connector C-109 (terminal 5).
Q: Is the wiring harness between A/C-ECU connector C-15 (terminal 16) and air mixing damper control motor and potentiometer connector C-109 (terminal 5) in good condition?
YES: It can be assumed that this malfunction is intermittent. Refer to How to Use Troubleshooting/Inspection Service Points - How to Cope with Intermittent Malfunctions.
NO: Repair the wiring harness.
STEP 10. Recheck for diagnostic trouble code.
Recheck if the DTC is set.
1. Erase the DTC.
2. Turn the ignition switch to "OFF" position.
3. Turn the ignition switch to "ON" position.
4. Drive the vehicle and check if the diagnostic trouble code is set.
Q: Is the check result satisfactory?
YES: It can be assumed that this malfunction is intermittent. Refer to How to Use Troubleshooting/Inspection Service Points - How to Cope with Intermittent Malfunctions.
NO: Replace the A/C-ECU.
STEP 11. Using scan tool MB991958, check actuator test.
1. Connect scan tool MB991958 to the data link connector.
2. Start the engine.
3. Use scan tool MB991958 to run the actuator test.
Item 42: air mix damper motor 0% (MAX COOL position)
Item 43: air mix damper motor 100% (MAX HOT position)
Item 44: air mix damper motor 50% (middle position)
- Check that the air mixing damper control motor operates.
4. Turn the ignition switch to the "LOCK" (OFF) position.
Q: Does the motor operate normally?
YES: Go to Step 13.
NO: Go to Step 12.
STEP 12. Recheck for diagnostic trouble code.
Recheck if the DTC is set.
1. Erase the DTC.
2. Turn the ignition switch to "OFF" position.
3. Turn the ignition switch to "ON" position.
4. Drive the vehicle and check if the diagnostic trouble code is set.
Q: Is the check result satisfactory?
YES: It can be assumed that this malfunction is intermittent. Refer to How to Use Troubleshooting/Inspection Service Points - How to Cope with Intermittent Malfunctions.
NO: Replace the A/C-ECU.
STEP 13. Check air mixing damper control motor and potentiometer connector C-109 for loose, corroded or damaged terminals, or terminals pushed back in the connector.
Q: Is air mixing damper control motor and potentiometer connector C-109 in good condition?
YES: Go to Step 14.
NO: Repair or replace the connector. Refer to Harness Connector Inspection.
STEP 14. Check the air mixing damper control motor and potentiometer.
CAUTION: Do not apply battery voltage when the damper is in the MAX COOL or MAX HOT position.
1. Operate the air mixing damper control motor as described in the table.
2. Measure the resistances between connector terminals 3 and 5, and between 3 and 7, while the air mixing damper control motor is running. The resistances should change gradually within the standard value.
Standard value: 1.7 (MAX HOT) - 5.0 (MAX COOL) kohms
Q: Are the air mixing damper control motor and potentiometer in good condition?
YES: Go to Step 15.
NO: Replace the air mixing damper control motor and potentiometer.
STEP 15. Check A/C-ECU connector C-15 for loose, corroded or damaged terminals, or terminals pushed back in the connector.
Q: Is A/C-ECU connectors C-15 in good condition?
YES: Go to Step 16.
NO: Repair or replace the connector. Refer to Harness Connector Inspection.
STEP 16. Check the wiring harness for open circuit.
1. Disconnect A/C-ECU connector C-15 and air mixing damper control motor and potentiometer connector C-109, and measure the resistance at the wiring harness side.
2. Measure the resistance between A/C-ECU connector C-15 terminal 20 and air mixing damper control motor and potentiometer connector C-109 terminal 1.
OK: Less than 2 ohms
Q: Is the check result normal?
YES: Go to Step 18.
NO: Go to Step 17.
STEP 17. Check the wiring harness between A/C-ECU connector C-15 (terminal 1) and air mixing damper control motor and potentiometer connector C-109 (terminal 1).
Q: Is the wiring harness between A/C-ECU connector C-15 (terminal 1) and air mixing damper control motor and potentiometer connector C-109 (terminal 1) in good condition?
YES: It can be assumed that this malfunction is intermittent. Refer to How to Use Troubleshooting/Inspection Service Points - How to Cope with Intermittent Malfunctions.
NO: Repair the wiring harness.