B1508

DTC B1508: Seat Slide Sensor System Fault Power Supply Circuit (Short-Circuited to Power Supply)

CAUTION:
If DTC B1508 is set in the combination meter, always diagnose the CAN bus lines.

CIRCUIT OPERATION

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

DTC SET CONDITIONS

- This DTC is set if there is abnormal resistance between the input terminals of the seat slide sensor:
- The most likely causes for this code to be set are the followings:
- Short to the power supply in the seat slide sensor harness
- Malfunction of the seat slide sensor

TROUBLESHOOTING HINTS

- Damaged wiring harnesses or connectors
- Short to the power supply in the seat slide sensor harness
- Malfunction of the SRS-ECU
- Malfunction of the seat slide sensor

DIAGNOSIS

Required Special Tools:

- 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
- MB991865: Dummy resistor
- MB991866: Resister harness

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

(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. Refer to "How to connect the scan tool Reading and Clearing Diagnostic Trouble Codes."
(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?

YES Go to Step 2.

NO Repair the CAN bus line CAN Bus Diagnostics Chart).

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?

YES Go to Step 3.

NO There is an intermittent malfunction such as poor engaged connector(s) or open circuit How to Cope With Intermittent Malfunctions).

STEP 3. Check the seat slide sensor circuit. Measure the voltage at the SRS-ECU connector C-122.

(1)Disconnect SRS-ECU connector C-122.

(2)Disconnect seat slide sensor connector D-24.
(3)Turn the ignition switch to the "ON" position.

(4)
CAUTION:
Do not insert a test probe into the terminal from its front side directly, as the connector contact pressure may be weakened.

Measure the voltage between C-122 harness side connector terminals 1, 2 and body ground.
Voltage should measure 0 volt.

Q. Is the measured voltage 0 volt?

YES Erase the diagnostic trouble code memory, and check the diagnostic trouble code. If DTC B1508 sets, check if the seat slide sensor is in good condition. If the sensor is in good condition, replace the SRS-ECU (Refer to Service and Repair). Then go to Step 5.

NO Go to Step 4.

STEP 4. Check the harness wires for short circuit to power supply between SRS-ECU connector C-122 (terminal No.2 and 1) and seat slide sensor connector D-24 (terminal No.1 and 2).

Q. Are the harness wires between SRS-ECU connector C-122 (terminal No.2 and 1) and seat slide sensor connector D-24 (terminal No.1 and 2) in good condition?

YES Go to Step 5.

NO Repair the harness wires between SRS-ECU connector C-122 and seat slide sensor connector D-24. Then go to Step 5.

STEP 5. Recheck for diagnostic trouble code.