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DTC 41

IG1 Power Supply Circuit System (Fuse 19 Circuit)

IG1 Power Supply Circuit (fuse No.19 Circuit):






CIRCUIT OPERATION
- The SRS-ECU is powered from the ignition switch (IG1).
- The SRS-ECU power is supplied from two circuits. Even if one circuit is shut off, the air bag can inflate.

DTC SET CONDITIONS
This DTC is set if the voltage between the IG1 terminals (fuse 19 circuit) and ground is lower than a pre-determined value for a continuous period of five second or more. However, if the vehicle condition returns to normal, DTC 41 will be automatically erased, and the SRS warning light will switch off.

TROUBLESHOOTING HINTS
- Damaged wiring harnesses or connectors
- Malfunction of the SRS-ECU

DIAGNOSIS

Required Special Tools:
- MB991502: Scan Tool (MUT-II)
- MB991223 (MB991222): Harness set (Probe)




STEP 1. Check junction block fuse number 19.

Q: Is the fuse burned out?

YES: Go to Step 4.

NO: Go to Step 2.

STEP 2. Check the power supply circuit for open circuit at SRS-ECU connector C-44.




1. Disconnect SRS-ECU connector C-44.

2. Connect the negative battery terminal.
3. 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.

4. Measure the voltage between C-44 harness connector terminal 12 and body ground. Voltage should measure 9 volts or more.

Q: Is the measured voltage within the specified range?

YES: Erase the DTC memory, and check for the diagnostic trouble code. If DTC 41 is set, replace the SRS-ECU. Then go to Step 10.

NO: Go to Step 3.










STEP 3. Check the harness for open circuit between SRS-ECU connector C-44 (terminal 12) and ignition switch connector C-58 (terminal 2).

NOTE: After inspecting intermediate connectors C-84 and C-87, inspect the wiring harness. If intermediate connectors are damaged, repair or replace them. Refer to Harness Connector Inspection. Then go to Step 10.

Q: Is the harness between SRS-ECU connector C-44 (terminal 12) and the ignition switch connector C-58 (terminal 2) in good condition?

YES: Go to Step 10.

NO: Repair the harness wire between SRS-ECU connector C-44 and the ignition switch connector C-58.Then go to Step 10.

STEP 4. Check a burned-out fuse.

1. Replace the fuse.
2. Turn the ignition switch to the "ON" position, wait for at least one minute and then turn the ignition switch to the "LOCK" (OFF) position.
3. Check the fuse.

Q: Is the fuse in good condition?

YES: Go to Step 10.

NO: Go to Step 5.

STEP 5. Check the SRS-ECU power supply circuit for short circuit to ground at the junction block connector C-84.




1. Disconnect junction block connector C-84, and measure at the harness connector.






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

2. Check for continuity between terminal 24 and body ground.
It should be open circuit.

Q: Does continuity exist?

NO: Go to Step 6.

YES: Go to Step 8.

STEP 6. Check the fuse number 19-related circuit at junction block connector C-84.




1. Disconnect junction block connector C-84, and measure at the harness connector.






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

2. Check for continuity between terminal 25 and body ground. It should be open circuit.

Q: Does continuity exist?

NO: Check the other circuits, which flow through fuse number 19.

YES: Go to Step 7.







STEP 7. Check the harness for short circuit to ground between junction block connector C-84 (terminal 25) and combination meter connector C-30 (terminal 3).

Q: Is the harness wire between junction block connector C-84 (terminal 25) and combination meter connector C-30 (terminal 3) in good condition?

YES: Go to Step 10.

NO: Repair the harness wire between junction block connector C-84 and combination meter connector C-30. Then go to Step 10.

STEP 8. Check the power supply circuit for short circuit to ground at SRS-ECU connector C-44.




1. Disconnect SRS-ECU connector C-44, and measure at the harness connector.






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

2. Check for continuity between terminal 12 and body ground.
It should be open circuit.

Q: Is the circuit normal?

YES: Erase the DTC memory, and check for the diagnostic trouble code, If DTC 41 is set, replace the SRS-ECU. Then go to Step 10.

NO: Go to Step 9.







STEP 9. Check the harness for short circuit to ground between SRS-ECU connector C-44 (terminal 12) and junction block connector C-84 (terminal 24).

Q: Is the harness wire between SRS-ECU connector C-44 (terminal 12) and junction block connector C-84 (terminal 24) in good condition?

YES: Go to Step 10.

NO: Repair the harness wire between SRS-ECU connector C-44 and junction block connector C-84. Then go to Step 10.

STEP 10. Check for the diagnostic trouble code.

Q: Is DTC 41 set?

YES: Return to Step 1.

NO: The procedure 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).
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