Inspection Procedure 7

INSPECTION PROCEDURE 7: When Sunlight Intensity Changes, Air Outlet Temperature does not Change.

Photo Sensor Motor Circuit:

FUNCTION
The resistance of the photo sensor varies by the volume of the insulation intensity of sun light, and the sensor sends the information to the A/C-ECU to control the temperature.

PROBABLE CAUSES
- Malfunction of the harness (photo sensor circuit is open/shorted to ground)
- Malfunction of the photo sensor
- Malfunction of the A/C-ECU
- Malfunction of connector.

DIAGNOSIS

Required Special Tools:
- MB991223: Harness Set
- MB992006: Extra Fine Probe
- MB991958: Scan Tool (MUT-III Sub Assembly)
- MB991824: V.C.I.
- MB991827: MUT-III USB Cable
- MB991910: MUT-III Main Harness A




STEP 1. Using scan tool MB991958, read 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 the check result satisfactory?

YES: Refer to Diagnostic Trouble Code Chart.

NO: Go to Step 2.

STEP 2. Using scan tool MB991958, check data list.

1. Connect scan tool MB991958 to the data link connector.
2. Start the engine.
3. Set scan tool MB991958 to the data reading mode.
- Item 06: Photo sensor
4. Cover the photo sensor with your hand or a shop towel.

NOTE: Check that the voltage displayed on the scan tool changes.

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

Q: Does the voltage displayed on the scan tool change?

when the photo sensor is covered?

YES: Go to Step 3.

NO: Go to Step 4.

STEP 3. Retest the system.

Check the trouble symptom again.

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 4. Check A/C-ECU connectors C-15, C-20 and photo sensor connector C-02 for loose, corroded or damaged terminals, or terminals pushed back in the connector.

Q: Are A/C-ECU connectors C-15, C-20 and photo sensor connector C-02 in good condition?

YES: Go to Step 5.

NO: Repair or replace the connector. Refer to Harness Connector Inspection. Check that the air conditioning works normally.

STEP 5. Check the wiring harness for open circuit.







1. Disconnect A/C-ECU connector C-15 and photo sensor connector C-02, and measure the resistance at the wiring harness side.




2. Measure the resistance between A/C-ECU connector C-15 terminal 19 and photo sensor connector C-02 terminal 1.

OK: Less than 2 ohms

Q: Is the check result normal?

YES: Go to Step 7.

NO: Go to Step 6.







STEP 6. Check the wiring harness between A/C-ECU connector C-15 (terminal 19) and photo sensor connector C-02 (terminal 1).

Q: Is the wiring harness between A/C-ECU connector C-15 (terminal 19) and photo sensor connector C-02 (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.

STEP 7. Check the wiring harness for open circuit.







1. Disconnect A/C-ECU connector C-20 and photo sensor connector C-02, and measure the resistance at the wiring harness side.




2. Measure the resistance between A/C-ECU connector C-20 terminal 25 and photo sensor connector C-02 terminal 2.

OK: Less than 2 ohms

Q: Is the check result normal?

YES: Go to Step 9.

NO: Go to Step 8.







STEP 8. Check the wiring harness between A/C-ECU connector C-20 (terminal 25) and photo sensor connector C-02 (terminal 2).

Q: Is the wiring harness between A/C-ECU connector C-20 (terminal 25) and photo sensor connector C-02 (terminal 2) 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 9. 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 19 and ground.

OK: 1.5 k ohms or more

Q: Does the measured resistance value correspond with this range?

YES: Go to Step 11.

NO: Go to Step 10.







STEP 10. Check the wiring harness between A/C-ECU connector C-15 (terminal 19) and photo sensor connector C-02 (terminal 1).

Q: Is the wiring harness between A/C-ECU connector C-15 (terminal 19) and photo sensor connector C-02 (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.

STEP 11. Measure the resistance at A/C-ECU connector C-20.




1. Disconnect A/C-ECU connector C-20, and measure the resistance at the wiring harness side.




2. Measure the resistance value between terminal 25 and ground

OK: 1.5 k ohms or more

Q: Does the measured resistance value correspond with this range?

YES: Go to Step 13.

NO: Go to Step 12.







STEP 12. Check the wiring harness between A/C-ECU connector C-20 (terminal 25) and photo sensor connector C-02 (terminal 2).

Q: Is the wiring harness between A/C-ECU connector C-20 (terminal 25) and photo sensor connector C-02 (terminal 2) 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 13. Replace the photo sensor and check the trouble symptom again.

Q: Is the check result normal?

YES: The procedure is complete.

NO: Replace the A/C-ECU.