Manual Air Conditioning

DTC B1041: Air Mixing Damper Control Motor and Potentiometer (Potentiometer system shorted to its power supply)














FUNCTION

Detect the position of air mixing damper from the drive motor.

DETECTION LOGIC

This code is set when the air mixing damper control motor and potentiometer do not send any signal to the A/C-ECU due to short to power supply of the air mixing damper control motor and potentiometer circuit.

PROBABLE CAUSES

- Malfunction of connector.
- Malfunction of the harness (air mixing damper control motor and potentiometer circuit is open/shorted to its power supply)
- Malfunction of the air mixing damper control motor and potentiometer.
- Malfunction of the A/C-ECU.

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, check data list.





(1)
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.

Connect scan tool MB991958 to the data link connector.
(2)Start the engine.
(3)Set scan tool MB991958 to the data reading mode.

- Item 63: Air mix potentiometer
- Item 64: Air mix potentiometer (Target)

NOTE:
Check that the set position of the heater control matches the displayed position on the scan tool.

(4)Turn the ignition switch to the "LOCK" (OFF) position.

Q. Does the heater control set position match the scan tool displayed position?

YES Go to Step 2.

NO Go to Step 3.

STEP 2. 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 that the diagnostic trouble code is not set.

Q. Is the check result satisfactory?

YES It can be assumed that this malfunction is intermittent. How to Cope With Intermittent Malfunctions.
NO Replace the heater control.
STEP 3. 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 4.

NO Repair or replace the connector. Harness Connector Inspection.

STEP 4. Check the air mixing damper control motor and potentiometer.





(1)
CAUTION:
Do not apply battery voltage when the damper is in the MAX COOL or MAX HOT position.

Operate the air mixing damper control motor as described in the table below.





(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-14 for loose, corroded or damaged terminals, or terminals pushed back in the connector.





Q. Is A/C-ECU connector C-14 in good condition?

YES Go to Step 6.

NO Repair or replace the connector. Harness Connector Inspection.

STEP 6. Check the wiring harness for open circuit.





(1)Disconnect A/C-ECU connector C-14 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-14 terminal 10 and air mixing damper control motor and potentiometer connector C-109 terminal 7.
OK: Less than 2 ohms

Q. Is the check result normal?

YES Go to Step 8.

NO Go to Step 7.

STEP 7. Check the wiring harness between A/C-ECU connector C-14 (terminal 10) and air mixing damper control motor and potentiometer connector C-109 (terminal 7).









NOTE:
Also check joint connector C-01 for loose, corroded, or damaged terminals, or terminals pushed back in the connector. If joint connector C-01 is damaged, repair or replace the connector as described in Harness Connector Inspection Harness Connector Inspection.

Q. Is the wiring harness between A/C-ECU connector C-14 (terminal 10) and air mixing damper control motor and potentiometer connector C-109 (terminal 7) in good condition?

YES It can be assumed that this malfunction is intermittent. How to Cope With Intermittent Malfunctions.

NO Repair the wiring harness.

STEP 8. Measure the voltage at A/C-ECU connector C-14.





(1)Disconnect A/C-ECU connector C-14, and measure the voltage at the wiring harness side.
(2)Turn the ignition switch to the "ON" position.
(3)Turn the temperature control dial to the MAX HOT position.





(4)Measure the voltage between terminal 12 and ground.
OK: 1.3 - 1.5 volts

Q. Is the check result normal?

YES Go to Step 10.

NO Go to Step 9.

STEP 9. Check the wiring harness between A/C-ECU connector C-14 (terminal 12) and air mixing damper control motor and potentiometer connector C-109 (terminal 3).





Q. Is the wiring harness between A/C-ECU connector C-14 (terminal 12) and air mixing damper control motor and potentiometer connector C-109 (terminal 3) in good condition?

YES It can be assumed that this malfunction is intermittent. 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. How to Cope With Intermittent Malfunctions.
NO Replace the heater control.