DTC 27

DTC 27: Driver's Seat Belt Pre-Tensioner (Squib) System Fault 2 (Open in the Squib Circuit)

Driver's Seat Belt Pre-tensioner (Squib):

CIRCUIT 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.

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

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

DIAGNOSIS

Required Special Tools:
- MB991958: Scan Tool (M.U.T.-III Sub Assembly)
- MB991824: V.C.I.
- MB991827: M.U.T.-III USB Cable
- MB991911: M.U.T.-III Main Harness B
- MB991865: Dummy resister
- MB991866: Resister harness (For Pre-tensioner)

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







1. Disconnect the negative battery terminal.
2. Disconnect the driver's seat belt pre-tensioner connector D-16. Use a flat-tipped screwdriver to unlock the locking button at the harness side connector by withdrawing it toward you in two stages, and then disconnect the connector.




3. Connect special tool MB991865 to special tool MB991884.
4. Connect special tool MB991884 to the D-16 harness connector.
5. Connect the negative battery terminal.
6. Erase the diagnostic trouble code memory, and check the diagnostic trouble code.

Q: Is DTC 27 set?

YES: Go to Step 2.

NO: Replace the driver'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.29 and 30) and the driver's seat belt pre-tensioner connector D-16 (terminal No.1 and 2).




1. Disconnect SRS-ECU connector C-13 and driver's seat belt pre-tensioner connector D-16, and measure at the wiring harness side. For connector D-16, use a flat-tipped screwdriver to unlock the locking button at the harness side connector by withdrawing it toward you in two stages, and then disconnect the connector.










2. Connect D-16 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. It should be less than 2 ohms.
- SRS-ECU connector C-13 (terminal No.29) and the special tool (terminal No.1)
- SRS-ECU connector C-13 (terminal No.30) and the special tool (terminal No.2)

Q: Does continuity exist?

YES: Erase the diagnostic trouble code memory, and check the diagnostic trouble code. If DTC 27 set, replace the SRS-ECU. Then go to Step 3.

NO: Repair harness wires between SRS-ECU connector C-13 and driver's seat belt pre-tensioner connector D-16. Then go to Step 3.

STEP 3. 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 DTC 27 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).