DTC 29

DTC 29: Passenger's (Front) Seat Belt Pre-Tensioner (Squib) System Fault 2 (Open in the Squib Circuit)

Passenger's (Front) Seat Belt Pre-Tensioner (Squib) Part 1:

Passenger's (Front) Seat Belt Pre-Tensioner (Squib) Part 2:

CIRCUIT OPERATION
The SRS-ECU judges how severe a collision is by detecting signals from 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.

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

TROUBLESHOOTING HITS
- Open circuit in the passenger's seat belt pre-tensioner (squib) circuit
- Improper connector contact
- Malfunction of the SRS-ECU

DIAGNOSIS

Required Special Tools:
- MB991958: Scan Tool (MUT-III Sub Assembly)
- MB991824: Vehicle Communication Interface (V.C.I.)
- MB991827: MUT-III USB Cable
- MB991911: MUT-III Main Harness B (Vehicles without CAN communication system)
- MB991865: Dummy resister
- MB991866: Resister harness (For Pre-tensioner)

STEP 1. Check the passenger's seat belt pre-tensioner. (Using scan tool MB991958, read the diagnostic trouble code.)

1. Disconnect the negative battery terminal.







2. Disconnect driver's seat belt pre-tensioner connector D-03. Use a flat-tipped screwdriver to pull out the locking button at the harness connector, and then disconnect the connector.




3. Connect special tool MB991865 to special tool MB991884.
4. Connect special tool MB991884 to the D-03 harness connector.
5. Connect the negative battery terminal.
6. Erase the diagnostic trouble code memory, and check the diagnostic trouble code.

Q: Is DTC 29 set?

YES: Go to Step 2.

NO: Replace the passenger's seat belt pre-tensioner. Then go to Step 3.

STEP 2. Check the harness for open circuit between SRS-ECU connector C-13 (terminal No.27 and 28) and the passenger's seat belt pre-tensioner connector D-03 (terminal No.1 and 2).










1. Disconnect SRS-ECU connector C-13 and driver's seat belt pre-tensioner connector D-03, and measure at the wiring harness side. For connector D-03, use a flat-tipped screwdriver to pull out the locking button at the harness side connector, and then disconnect the connector.




2. Connect D-03 harness connector to special tool MB991884.




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

3. Check for continuity between the following terminals.
- SRS-ECU connector C-13 (terminal No.27) and special tool (MB991884) connector (terminal No.2)
- SRS-ECU connector C-13 (terminal No.28) and special tool (MB991884) connector (terminal No.1) It should be less than 2 Ohms.

Q: Does continuity exist?

YES: Erase the diagnostic trouble code memory, and check the diagnostic trouble code. If DTC 29 sets, replace the SRS-ECU. Then go to Step 3.

NO: Repair the harness wires between SRS-ECU connector C-13 passenger's seat belt pre-tensioner connector D-03. Then go to Step 3.

STEP 3. Recheck for diagnostic trouble code.

Q: Is DTC 29 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 How to Use Troubleshooting/Inspection Service Points - How to Cope with Intermittent Malfunction)