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
- If front air bag analog G-sensor and front air bag safing G-sensor inside the SRS-ECU sense a predetermined collision energy simultaneously during a frontal collision, the SRS-ECU sends igniting signal to the pre-tensioner, causing the pre-tensioner to operate.

DTC SET CONDITIONS
- These DTC are output 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:
- MB991502: Scan Tool (MUT-II)
- MB991865: Dummy resister
- MB991866: Resister harness

STEP 1. Check the driver's seat belt pre-tensioner.

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




1. Connect special tool MB991865 to special tool MB991866.
2. Disconnect the driver's seat belt pre-tensioner connector D-16, and insert special tool MB991866 into the harness side connector by backprobing.
3. Connect the negative battery terminal.
4. Erase DTC memory, and then recheck the DTC.

Q: Is DTC 27 output?

YES: Go to Step 2.
NO: Replace the driver's seat belt pre-tensioner. Then go to Step 4.

Connector:

STEP 2. Check the harness for open circuit between SRS-ECU and the driver's seat belt pre-tensioner.
Measure at SRS-ECU connector C-13 and driver's seat belt pre-tensioner connector D-16.

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

1. Disconnect SRS-ECU connector C-13 and driver's seat belt pre-tensioner connector D-16, and measure at the wiring harness side.




2. Check the continuity between the following terminals.

C-13 connector D-16 connector
30 1
29 2

- Should be less than 2 ohm.

Q: Is the continuity normal?

YES: Erase the DTC memory, and recheck if any DTC sets. If DTC 27 sets, replace the SRS-ECU. Then go to Step 4.
NO: Go to Step 3.

Connector:

STEP 3. Check the harness for open circuit between SRS-ECU connector C-13 and driver's seat belt pre-tensioner connector D-16.

NOTE: After inspecting intermediate connector C-128, inspect the wiring harness.

If the intermediate connector C-128 is damaged, repair or replace it. Refer to Harness Connector Inspection. Go to step 4.

Q: Are harness wires SRS-ECU connector C-13 and driver's seat belt pre-tensioner connector D-16 in good condition?

YES: Go to step 4.
NO: Repair harness wires between SRS-ECU connector C-13 and driver's seat belt pre-tensioner connector D16. Then go to step 4.

STEP 4. Check for DTC.

Q: Is DTC 27 output?

YES: Return to step 1.
NO: This diagnosis is complete. (If no malfunctions are not found in all steps, an intermittent malfunction is suspected. Refer to How to Use Troubleshooting/Inspection Service Points - How to Cope with Intermittent Malfunction.)