DTC 41

IG1 Power Circuit System (Fuse No. 2 Circuit)

IG1 Power Circuit (Fuse No.2 Circuit Or No.3 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.
- The SRS-ECU judges how severe a collision is by detecting signals from the left and right side impact sensors and the analog G-sensor. If the impact is over a predetermined level, the SRS-ECU outputs an ignition signal. At this time, if the safing G-sensor is on, the SRS air bag will inflate.

DTC SET CONDITIONS
These DTC are output if the voltage between the IG1 terminals (fuse No. 2 or No. 3 circuit) and ground is lower than a predetermined value for a continuous period of five second or more. However, if the vehicle condition returns to normal, DTC numbers 41 or 42 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




STEP 1. Check the ignition switch (IG1) line at the SRS-ECU connector C-72 by backprobing.
1. Do disconnect the connector C-72.
2. Connect the negative battery terminal.
3. Turn the ignition switch to the "ON" position.
4. Measure the voltage between terminal 12 (for DTC 41) or 9 (for DTC 42) and the ground by backprobing.

- Voltage should be 9 volts or more

Q: Is the voltage 9 volts or more?

YES: Go to Step 3.

NO: Go to Step 2.







STEP 2. Check the harness wires between the ignition switch (IG1) and SRS-ECU connector C-72.

NOTE: After inspecting intermediate connectors C-108 and C-111, inspect the wires. If intermediate connectors are damaged, repair or replace them. Refer to Harness Connector Inspection. Then go to Step 5.

Q: Are the harness wires between the ignition switch (IG1) and SRS-ECU connector C-72 in good condition?

YES: Go to Step 5.

NO: Repair them. Then go to Step 5.




STEP 3. Check the ground line at the SRS-ECU connector C-72 by backprobing.
1. Do disconnect the connector C-72.
2. Measure the resistance between terminal 3 and ground by backprobing.

Q: Is the resistance between terminal 3 and ground less than 2 ohm?

YES: Replace the SRS-ECU. Then go to Step 5.

NO: Go to Step 4.




STEP 4. Check the harness wire between SRS-ECU connector C-72 and ground.

Q: Is the harness wire between SRS-ECU connector C-72 and ground in good condition?

YES: Go to Step 5.

NO: Repair it. Then go to Step 5.

STEP 5. Check for DTC.

Q: Is any of DTC 41 or 42 output?

YES: Replace the SRS-ECU.

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.)