Diagnosis code 68: Passenger's Seat Belt Pre-Tensioner (Squib) System Fault for Power Supply Circuit (Short-Circuited to Power Supply)

OPERATION

The SRS-ECU judges how severe a collision is by detecting signals from the front impact sensors and the front air bag analog G-sensor. If the impact is over a predetermined level, the SRS-ECU outputs an ignition signal. At this time, if the front air bag safing G-sensor is on, the pre-tensioner will deploy.

DIAGNOSIS CODE SET CONDITIONS

This diagnosis code is set if there is abnormal resistance between the input terminals of the passenger's seat belt pre-tensioner (squib).

PROBABLE CAUSES

Damaged wiring harnesses or connectors

Short to the power supply in the passenger's seat belt pre-tensioner (squib) harness

Malfunction of the SRS-ECU

DIAGNOSIS PROCEDURE

STEP 1. Check the passenger's seat belt pre-tensioner (Check whether the diagnosis code is reset.).

Disconnect the negative battery terminal.

Disconnect passenger's seat belt pre-tensioner connector D-29 <2000> or D-43 <2400>. Use a flat-tipped screwdriver to pull out the locking button at the harness side connector, and then disconnect the connector.

Connect special tool dummy resistor (MB991865) to special tool resistor harness (MB991884).

Connect special tool MB991884 to the D-29 <2000> or D-43 <2400> harness side connector.

Connect the negative battery terminal.

Erase diagnosis code memory, and then check the diagnosis code.

Q: Is diagnosis code 68 set?

YES: Go to Step 2

.
NO: Replace the passenger's seat belt pre-tensioner (Refer to

). Then go to Step 4

STEP 2. Check the passenger's seat belt pre-tensioner at the SRS-ECU connector C-114.

Disconnect SRS-ECU connector C-114.

Disconnect passenger's seat belt pre-tensioner connector D-29 <2000> or D-43 <2400>. Use a flat-tipped screwdriver to pull out the locking button at the harness side connector, and then disconnect the connector.

Turn the ignition switch to the "ON" position,

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-114 harness side connector terminals No.27, 28 <except 2400 (RH drive vehicles)>, No.29, 30 <2400 (RH drive vehicles)> and body earth.

OK: 0 V

Q: Is the check result normal?

YES: Erase the diagnosis code memory, and check the diagnosis code. If diagnosis code 68 sets, replace the SRS-ECU (Refer to

). Then go to Step 4

.
NO: Go to Step 3

STEP 3. Check the harness wires for short circuit to power supply between SRS-ECU connector C-114 (terminal No.27 and 28 <except 2400 (RH drive vehicles)>, No.29 and 30 <2400 (RH drive vehicles)>) and passenger's seat belt pre-tensioner connector D-29 <2000> or D-43 <2400> (terminal No.1 and 2).

NOTE: After inspecting intermediate connector C-117 <2000>, inspect the wiring harness. If the intermediate connector C-117 <2000> is damaged, repair or replace it. Then go to Step 4

Q: Are the harness wires between SRS-ECU connector C-114 (terminal No.27 and 28 <except 2400 (RH drive vehicles)>, No.29 and 30 <2400 (RH drive vehicles)>) and passenger's seat belt pre-tensioner connector D-29 <2000> or D-43 <2400> (terminal No.1 and 2) in good condition?

YES: Go to Step 4

.
NO: Repair the harness wires between SRS-ECU connector C-114 and passenger's seat belt pre-tensioner connector D-29 <2000> or D-43 <2400>. Then go to Step 4

STEP 4. Check whether the diagnosis code is reset.

Q: Is diagnosis code 68 set?

YES: Return to Step 1

.
NO: The procedure is complete (If no malfunctions are found in all steps, an intermittent malfunction is suspected). Refer to GROUP 00 - How to Use Troubleshooting/Inspection Service Points


Diagnosis code 68: Passenger's Seat Belt Pre-Tensioner (Squib) System Fault for Power Supply Circuit (Short-Circuited to Power Supply)

OPERATION The SRS-ECU judges how severe a collision is by detecting signals from the front impact sensors and the front air bag analog G-sensor. If the impact is over a predetermined level, the SRS-ECU outputs an ignition signal. At this time, if the front air bag safing G-sensor is on, the pre-tensioner will deploy.
DIAGNOSIS CODE SET CONDITIONS This diagnosis code is set if there is abnormal resistance between the input terminals of the passenger's seat belt pre-tensioner (squib).
PROBABLE CAUSES Damaged wiring harnesses or connectors Short to the power supply in the passenger's seat belt pre-tensioner (squib) harness Malfunction of the SRS-ECU
	DIAGNOSIS PROCEDURE

	STEP 1. Check the passenger's seat belt pre-tensioner (Check whether the diagnosis code is reset.). Disconnect the negative battery terminal.
	Disconnect passenger's seat belt pre-tensioner connector D-29 <2000> or D-43 <2400>. Use a flat-tipped screwdriver to pull out the locking button at the harness side connector, and then disconnect the connector.
	Connect special tool dummy resistor (MB991865) to special tool resistor harness (MB991884). Connect special tool MB991884 to the D-29 <2000> or D-43 <2400> harness side connector. Connect the negative battery terminal. Erase diagnosis code memory, and then check the diagnosis code. Q: Is diagnosis code 68 set? YES: Go to Step 2. NO: Replace the passenger's seat belt pre-tensioner (Refer to ). Then go to Step 4.
	STEP 2. Check the passenger's seat belt pre-tensioner at the SRS-ECU connector C-114. Disconnect SRS-ECU connector C-114.
	Disconnect passenger's seat belt pre-tensioner connector D-29 <2000> or D-43 <2400>. Use a flat-tipped screwdriver to pull out the locking button at the harness side connector, and then disconnect the connector. Turn the ignition switch to the "ON" position,
	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-114 harness side connector terminals No.27, 28 <except 2400 (RH drive vehicles)>, No.29, 30 <2400 (RH drive vehicles)> and body earth. OK: 0 V Q: Is the check result normal? YES: Erase the diagnosis code memory, and check the diagnosis code. If diagnosis code 68 sets, replace the SRS-ECU (Refer to ). Then go to Step 4 . NO: Go to Step 3.
	STEP 3. Check the harness wires for short circuit to power supply between SRS-ECU connector C-114 (terminal No.27 and 28 <except 2400 (RH drive vehicles)>, No.29 and 30 <2400 (RH drive vehicles)>) and passenger's seat belt pre-tensioner connector D-29 <2000> or D-43 <2400> (terminal No.1 and 2). NOTE: After inspecting intermediate connector C-117 <2000>, inspect the wiring harness. If the intermediate connector C-117 <2000> is damaged, repair or replace it. Then go to Step 4 . Q: Are the harness wires between SRS-ECU connector C-114 (terminal No.27 and 28 <except 2400 (RH drive vehicles)>, No.29 and 30 <2400 (RH drive vehicles)>) and passenger's seat belt pre-tensioner connector D-29 <2000> or D-43 <2400> (terminal No.1 and 2) in good condition? YES: Go to Step 4. NO: Repair the harness wires between SRS-ECU connector C-114 and passenger's seat belt pre-tensioner connector D-29 <2000> or D-43 <2400>. Then go to Step 4.
	STEP 4. Check whether the diagnosis code is reset. Q: Is diagnosis code 68 set? YES: Return to Step 1 . NO: The procedure is complete (If no malfunctions are found in all steps, an intermittent malfunction is suspected). Refer to GROUP 00 - How to Use Troubleshooting/Inspection Service Points .