DTC B1B8C: Driver Seat Slide Sensor Circuit Performance

caution

If DTC B1B8C is set in the occupant classification-ECU, always diagnose the CAN main bus lines.

CIRCUIT OPERATION

The seat slide sensor sets the current value Hi or Low determined by the seat position.
The occupant classification-ECU determines the seat position according to the current value from the seat slide sensor.

DTC SET CONDITION

The DTC is set when the seat slide sensor output current is not within the specified range.

TROUBLESHOOTING HINTS

The seat slide sensor may be defective.
The wiring harness or connectors may have loose, corroded, or damaged terminals, or terminals pushed back in the connector
Malfunction of the occupant classification-ECU

DIAGNOSIS

Required Special Tools:

MB991958 Scan Tool (M.U.T.-III Sub Assembly)

MB991824: Vehicle Communication Interface (V.C.I.)
MB991827 M.U.T.-III USB Cable
MB991910 M.U.T.-III Main Harness A (Vehicles with CAN communication system)

STEP 1. Using scan tool MB991958, diagnose the CAN bus line.

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.

(1)Connect scan tool MB991958. Refer to "How to connect the scan tool

."
(2)Turn the ignition switch to the "ON" position.
(3)Diagnose the CAN bus line.
(4)Turn the ignition switch to the "LOCK" (OFF) position.

Q. Is the CAN bus line found to be normal?

Go to Step 2.

Repair the CAN bus line (Refer to GROUP 54C, Diagnosis

STEP 2. Recheck for diagnostic trouble code.

Check again if the DTC is set.

(1)Erase the DTC.

(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 DTC set?

	Go to Step 3.

	There is an intermittent malfunction such as poor engaged connector(s) or open circuit (Refer to GROUP 00, How to Cope with Intermittent Malfunction ).

STEP 3. Check the occupant classification-ECU connector D-35-2, front seat assembly connector D-35 and seat slide sensor connector D-28 for loose, corroded or damaged terminals, or terminals pushed back in the connector.

Q. Is the occupant classification-ECU connector D-35-2, front seat assembly connector D-35 and seat slide sensor connector D-28 in good condition?

	Go to Step 4.

	Replace the component(s) (Refer to GROUP 00E, Harness Connector Inspection ).

STEP 4. Check the harness for open circuit between occupant classification-ECU connector D-35-2 (terminal No.27 and 29) and the seat slide sensor connector D-28 (terminal No.2 and 1).

(1)Disconnect occupant classification-ECU connector D-35-2 and seat slide sensor connector D-28.

(2)

caution

Do not insert a test probe into the terminal from its front side directly, as the connector contact pressure may be weakened.

Check for continuity between the following terminals. It should be less than 2 ohms.

Occupant classification-ECU connector D-35-2 (terminal No.27) and the seat slide sensor connector D-28 (terminal No.2)
Occupant classification-ECU connector D-35-2 (terminal No.29) and the seat slide sensor connector D-28 (terminal No.1)

Q. Does continuity exist?

Go to Step 5.

Repair the harness wires between occupant classification-ECU connector D-35-2 and seat slide sensor connector D-28.

STEP 5. Check the seat slide sensor circuit. Measure the resistance at occupant classification-ECU connector D-35-2.

(1)Disconnect occupant classification connector-ECU connector D-35-2.

(2)Disconnect seat slide sensor connector D-28.

(3)

caution

Do not insert a test probe into the terminal from its front side directly, as the connector contact pressure may be weakened.

Check for continuity between D-35-2 harness side connector terminals 27 and 29.
It should be open circuit.

Q. Is it open circuit?

Go to Step 6.

Repair the harness wires between occupant classification-ECU connector D-35-2 and seat slide sensor connector D-28.

STEP 6. Check the harness for open circuit between occupant classification-ECU connector D-35-2.

(1)Disconnect occupant classification-ECU connector D-35-2 and seat slide sensor connector D-28.

(2)

caution

Do not insert a test probe into the terminal from its front side directly, as the connector contact pressure may be weakened.

Check for continuity between D-35-2 Occupant classification-ECU connector terminals No.27, 29 and body ground.
It should be open circuit.

Q. Is it open circuit?

Go to Step 7

Repair the harness wires between occupant classification-ECU connector D-35-2 and seat slide sensor connector D-28.

STEP 7. Recheck for diagnostic trouble code.

Check again if the DTC is set to the occupant classification-ECU.

(1)Erase the DTC.

(2)Turn the ignition switch from "LOCK" (OFF) position to "ON" position.

(3)Check if DTC is set.

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

Q. Is the DTC set?

	Replace the front seat cushion frame (LH) (Refer to GROUP 52A, Front Seat Assembly ) <Except RALLIART> or replace the slide adjuster (LH) (Refer to GROUP 52A, Front Seat Assembly ) <RALLIART>. Then go to Step 8.

	There is an intermittent malfunction such as poor engaged connector(s) or open circuit (Refer to GROUP 00, How to Cope with Intermittent Malfunction ).

STEP 8. Recheck for diagnostic trouble code.

Check again if the DTC is set to the occupant classification-ECU.

(1)Erase the DTC.

(2)Turn the ignition switch from "LOCK" (OFF) position to "ON" position.

(3)Check if DTC is set.

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

Q. Is the DTC set?

	Replace the front seat cushion frame (RH) (Refer to GROUP 52A, Front Seat Assembly ) <Except RALLIART> or replace the slide adjuster (RH) (Refer to GROUP 52A, Front Seat Assembly ) <RALLIART>.

	There is an intermittent malfunction such as poor engaged connector(s) or open circuit (Refer to GROUP 00, How to Cope with Intermittent Malfunction ).