Diagnosis code 42: IG1 Power Supply Circuit System (Fuse No.3 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.

DIAGNOSIS CODE SET CONDITIONS

This diagnosis code is set if the voltage between the IG1 terminals (fuse No.3 circuit) and earth is lower than a predetermined value for a continuous period of 5 second or more. However, if the vehicle condition returns to normal, diagnosis code number 42 will be automatically erased, and the SRS warning lamp will switch off.

PROBABLE CAUSES

Damaged wiring harnesses or connectors

Malfunction of the SRS-ECU

DIAGNOSIS PROCEDURE

STEP 1. Check junction block fuse number 3.

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-115.

Disconnect the negative battery terminal.

Disconnect SRS-ECU connector C-115.

Connect the negative battery terminal.

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.

Measure the voltage between C-115 harness side connector terminal 13 and body earth.

OK: 9 V or more

Q: Is the check result normal?

YES: Erase the diagnosis connector memory, and check the diagnosis code. If diagnosis code 42 sets, replace the SRS-ECU (Refer to

). Then go to Step 8

.
NO: Go to Step 3

STEP 3. Check the harness for open circuit between SRS-ECU connector C-115 (terminal No.13) and the ignition switch connector C-303 (terminal No.2).

NOTE: After inspecting intermediate connectors C-205 and C-203, inspect the wiring harness. If intermediate connectors are damaged, repair or replace them. Then go to Step 8

Q: Is the harness wire between SRS-ECU connector C-115 (terminal No.13) and the ignition switch connector C-303 (terminal No.2) in good condition?

YES: Go to Step 8

.
NO: Repair the harness wire between SRS-ECU connector C-115 and the ignition switch connector C-303. Then go to Step 8

STEP 4. Check a burned-out fuse.

Replace the fuse.

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.

Check the fuse.

Q: Is the fuse in good condition?

YES: Go to Step 8

.
NO: Go to Step 5

STEP 5. Check the SRS-ECU power supply circuit for short circuit to earth at the junction block connector C-205.

Disconnect junction block connector C-205, and measure at the wiring harness side.

CAUTION

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

Check for continuity between terminal 7 and body earth.
OK: Open circuit

Q: Is the check result normal?

YES: Check the other circuit, which flows through fuse number 3.
NO: Go to Step 6

STEP 6. Check the power supply circuit for short circuit to earth at the SRS-ECU connector C-115.

Disconnect SRS-ECU connector C-115, and measure at the wiring harness side.

CAUTION

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

Check for continuity between terminal 13 and body earth.

OK: Open circuit

Q: Is the check result normal?

YES: Erase the diagnosis code memory, and check the diagnosis code. If diagnosis code 42 sets, replace the SRS-ECU. (Refer to

). Then go to Step 8

.
NO: Go to Step 7

STEP 7. Check the harness for short circuit to earth between SRS-ECU connector C-115 (terminal No.13) and junction block connector C-205 (terminal No.7).

Q: Is the harness wire between SRS-ECU connector C-115 (terminal No.13) and junction block connector C-205 (terminal No.7) in good condition?

YES: Go to Step 8

.
NO: Repair the harness wire between SRS-ECU connector C-115 and junction block connector C-205. Then go to Step 8

STEP 8. Check whether the diagnosis code is reset.

Q: Is diagnosis code 42 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 GROUP 00 - How to Use Troubleshooting/Inspection Service Points


Diagnosis code 42: IG1 Power Supply Circuit System (Fuse No.3 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.
DIAGNOSIS CODE SET CONDITIONS This diagnosis code is set if the voltage between the IG1 terminals (fuse No.3 circuit) and earth is lower than a predetermined value for a continuous period of 5 second or more. However, if the vehicle condition returns to normal, diagnosis code number 42 will be automatically erased, and the SRS warning lamp will switch off.
PROBABLE CAUSES Damaged wiring harnesses or connectors Malfunction of the SRS-ECU
	DIAGNOSIS PROCEDURE

	STEP 1. Check junction block fuse number 3. 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-115. Disconnect the negative battery terminal. Disconnect SRS-ECU connector C-115. Connect the negative battery terminal. 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. Measure the voltage between C-115 harness side connector terminal 13 and body earth. OK: 9 V or more Q: Is the check result normal? YES: Erase the diagnosis connector memory, and check the diagnosis code. If diagnosis code 42 sets, replace the SRS-ECU (Refer to ). Then go to Step 8. NO: Go to Step 3.
	STEP 3. Check the harness for open circuit between SRS-ECU connector C-115 (terminal No.13) and the ignition switch connector C-303 (terminal No.2). NOTE: After inspecting intermediate connectors C-205 and C-203, inspect the wiring harness. If intermediate connectors are damaged, repair or replace them. Then go to Step 8 . Q: Is the harness wire between SRS-ECU connector C-115 (terminal No.13) and the ignition switch connector C-303 (terminal No.2) in good condition? YES: Go to Step 8. NO: Repair the harness wire between SRS-ECU connector C-115 and the ignition switch connector C-303. Then go to Step 8.
	STEP 4. Check a burned-out fuse. Replace the fuse. 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. Check the fuse. Q: Is the fuse in good condition? YES: Go to Step 8 . NO: Go to Step 5.
	STEP 5. Check the SRS-ECU power supply circuit for short circuit to earth at the junction block connector C-205. Disconnect junction block connector C-205, and measure at the wiring harness side.
	CAUTION Do not insert a test probe into the terminal from its front side directly as the connector contact pressure may be weakened. Check for continuity between terminal 7 and body earth. OK: Open circuit Q: Is the check result normal? YES: Check the other circuit, which flows through fuse number 3. NO: Go to Step 6.
	STEP 6. Check the power supply circuit for short circuit to earth at the SRS-ECU connector C-115. Disconnect SRS-ECU connector C-115, and measure at the wiring harness side.
	CAUTION Do not insert a test probe into the terminal from its front side directly as the connector contact pressure may be weakened. Check for continuity between terminal 13 and body earth. OK: Open circuit Q: Is the check result normal? YES: Erase the diagnosis code memory, and check the diagnosis code. If diagnosis code 42 sets, replace the SRS-ECU. (Refer to ). Then go to Step 8 . NO: Go to Step 7.
	STEP 7. Check the harness for short circuit to earth between SRS-ECU connector C-115 (terminal No.13) and junction block connector C-205 (terminal No.7). Q: Is the harness wire between SRS-ECU connector C-115 (terminal No.13) and junction block connector C-205 (terminal No.7) in good condition? YES: Go to Step 8 . NO: Repair the harness wire between SRS-ECU connector C-115 and junction block connector C-205. Then go to Step 8.
	STEP 8. Check whether the diagnosis code is reset. Q: Is diagnosis code 42 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 GROUP 00 - How to Use Troubleshooting/Inspection Service Points .