SRS Warning Light Drive Circuit System Fault 1 (Light Does Not Switch Off)
DTC 43 - SRS Warning Light Drive Circuit System (Light does not switch off.)DTC 43, 44 - SRS Warning Light Drive Circuit:
Connector - C-41, C-42, C-72, C-101, C-104:
CIRCUIT OPERATION
Power for the SRS warning light is supplied from the ignition switch (IG1) circuit.
The SRS warning light illuminates when the ignition switch is turned "ON", and goes out after approximately seven seconds if there is not a malfunction in the SRS system.
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
This diagnostic trouble code is output when an open circuit is detected for a continuous period of five seconds while the SRS-ECU is monitoring the SRS warning light and the light is OFF (transistor OFF.) However, if the vehicle condition returns to normal, diagnostic trouble code number 43 will be automatically erased, and the SRS warning light will go out.
This diagnostic trouble code is output when a short to ground occurs in the harness between the SRS warning light and SRS-ECU while SRS-ECU is monitoring the light and the light is ON.
This diagnostic trouble code is output under one of the following cases while the SRS-ECU is monitoring the warning light drive circuit:
- When a short circuit occurs in the warning light drive circuit.
- When a malfunction is detected in the output transistor inside the SRS-ECU.
However, if the vehicle returns to normal condition, diagnostic trouble code 44 will be automatically erased, and the SRS warning light will go out.
TROUBLESHOOTING HINTS
- Damaged wiring harnesses of connectors
- Blown bulb
- Malfunction of the SRS-ECU
- Malfunction of the combination meter
DIAGNOSIS
Required Special Tool:
MB991223 (MB991222): Harness set (Probe)
STEP 1. Check the SRS warning light line at SRS-ECU connector C-72.
1. Disconnect SRS-ECU connector C-72 and measure at the harness side.
2. Connect the negative battery cable.
3. Turn the ignition switch to "ON" position.
4. Use special tool MB991223 (MB991222) to connect terminal 4 to ground. The SRS warning light should illuminate.
If the light does not illuminate, go to Step 2.
If the light illuminates, replace the SRS-ECU.
Then go to Step 6.
STEP 2. Check the SRS warning light bulb.
If the SRS warning light bulb has blown, replace it. Then go to Step 6.
If the SRS warning light bulb has not blown, go to Step 3.
STEP 3. Check the harness wires between the ignition switch (IG1) and SRS-ECU connector C-72.
NOTE: After inspecting intermediate connectors C-42, C-41, C-104, C-101 inspect the wiring harness. If intermediate connectors C-42, C-41, C-104, C-101 are damaged, repair or replace them. Refer to General Information, Harness Connector Inspection.
Then go to Step 6.
If the harness wires are in good condition, go to Step 4. If any harness wires between ignition switch (IG1) and SRS-ECU connector C-72 are damaged, repair them. Then go to Step 6.
STEP 4. Check the ground line at the SRS-ECU connector C-72.
Use special tool MB991223 (MB991222) measure the resistance between terminal 3 and ground.
Should be less than 2 ohms.
If open circuit, go to Step 5.
If less than 2 ohms, go to Step 6.
STEP 5. Check the harness wires between SRS-ECU connector C-72 and ground.
If the harness wires are in good condition, go to Step 6. If any harness wires between SRS-ECU connector C-72 and ground are damaged, repair them. Then go to Step 6.
STEP 6. Check the diagnostic trouble codes.
Confirm that diagnostic trouble codes 43 and 44 are not output.