B1001

DTC B1001: Heater Air Intake Duct Sensor System (Short Circuit)










FUNCTION

The Heater Air Intake Duct Sensor has characteristics that the resistance drops when the temperature rises, and it sends the information of the temperature inside the vehicle to the A/C-ECU to control the temperature.

DETECTION LOGIC

This code is set when the Heater Air Intake Duct Sensor circuit (power supply side) is shorted to ground.

PROBABLE CAUSES

- Malfunction of connector.
- Malfunction of the harness.
- Malfunction of the heater air intake duct sensor.
- 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 01: Interior temperature sensor
- Check that the interior temperature matches the displayed value on the scan tool.

NOTE:
When this DTC is set and the system is in fail-safe status, the value of service data displays 25°C (77°F).

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

Q. Does the interior temperature match the displayed value on the scan tool?

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 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 A/C-ECU.
STEP 3. Check heater air intake duct sensor connector C-105 for loose, corroded or damaged terminals, or terminals pushed back in the connector.





Q. Is heater air intake duct sensor connector C-105 in good condition?

YES Go to Step 4.

NO Repair or replace the connector. Harness Connector Inspection.

STEP 4. Check the heater air intake duct sensor.





(1)Disconnect heater air intake duct sensor connector C-105.





(2)When the resistance between the sensor terminals is measured under two or more temperature conditions, the resistance should approximately satisfy the illustrated values.
NOTE:
The temperature conditions when checking should not exceed the range shown in the diagram.

Q. Is the heater air intake duct sensor in good condition?

YES Go to Step 5.

NO Replace the heater air intake duct sensor.

STEP 5. Check A/C-ECU connector C-20 for loose, corroded or damaged terminals, or terminals pushed back in the connector.





Q. Is A/C-ECU connectors C-20 in good condition?

YES Go to Step 6.

NO Repair or replace the connector. Harness Connector Inspection.

STEP 6. 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 22 and ground.
OK: 1 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-20 (terminal 22) and heater air intake duct sensor connector C-105 (terminal 2).





Q. Is the wiring harness between A/C-ECU connector C-20 (terminal 22) and heater air intake duct sensor connector C-105 (terminal 2) 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. 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 A/C-ECU.