SRS-ECU
DTC B210D: Battery Abnormal Low VoltageIG1 Power Supply Circuit:
CAUTION: If the diagnostic trouble code B210D is set in the SRS-ECU, always diagnose the CAN main bus line.
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 No.12 circuit or fuse No.18 circuit) and ground is lower than a predetermined value for a continuous period of five second or more.
TROUBLESHOOTING HINTS
- Battery voltage drop
- Open circuit to power supply circuit
- Damaged wiring harnesses or connectors
- Malfunction of the SRS-ECU
DIAGNOSIS
Required Special Tools:
- MB991958: Scan Tool (M.U.T.-III Sub Assembly)
- MB991824: Vehicle Communication Interface (V.C.I.)
- MB991827: M.U.T.-III USB Cable
- MB991910: M.U.T.-III Main Harness A (Vehicles with CAN communication system)
STEP 1. Battery voltage check Check the battery voltage.
Q: Is the check result normal?
YES : Go to Step 2.
NO : Charge or replace the battery.
STEP 2. Using scan tool MB991958, diagnose the CAN bus line.
CAUTION: To prevent damage to scan tool MB991958, always turn the ignition switch to the "LOCK" (OFF) position before connecting or disconnecting scan tool MB991958.
1. Connect scan tool MB991958. Refer to "How to connect the scan tool". Scan Tool Connecting
2. Turn the ignition switch to the "ON" position.
3. Diagnose the CAN bus line.
4. Turn the ignition switch to the "LOCK" (OFF) position.
Q: Is the CAN bus line found to be normal?
YES : Go to Step 3.
NO : Repair the CAN bus line (Refer to Controller area network Diagnosis).
STEP 3. Using scan tool MB991958, diagnose the ETACS.
CAUTION: To prevent damage to scan tool MB991958, always turn the ignition switch to the "LOCK" (OFF) position before connecting or disconnecting scan tool MB991958.
1. Connect scan tool MB991958. Refer to "How to connect the scan tool". Scan Tool Connecting
2. Turn the ignition switch to the "ON" position.
3. Check if the DTC is set.
4. Turn the ignition switch to the "LOCK" (OFF) position.
Q: Is the DTC set?
YES : Diagnose the ETACS (Refer to Interior ETACS, Diagnosis).
NO : Go to Step 4.
STEP 4. Recheck for diagnostic trouble code.
Check again if the DTC is set.
1. Erase the DTC.
2. Turn the ignition switch to "ON" position.
3. Check if the DTC is set.
4. Turn the ignition switch to the "LOCK" (OFF) position.
Q: Is the DTC set?
YES : Go to Step 5.
NO : There is an intermittent malfunction such as poor engaged connector(s) or open circuit (Refer to general (body and chassis) How to Cope with Intermittent Malfunction).
STEP 5. Check ETAS-ECU fuse number 12 or 18.
Q: Is the fuse burned out?
YES : Go to Step 8.
NO : Go to Step 6.
STEP 6. Check the power supply circuit for open circuit. Measure the voltage at SRS-ECU connector C-30.
1. Disconnect the negative battery terminal.
2. Disconnect SRS-ECU connector C-30.
3. While pushing the part "A" indicated in the figure of the harness side connector, turn the lock lever to the direction of the arrow to release the lock lever, and disconnect the C-30 SRS-ECU connector.
4. Connect the negative battery terminal.
5. 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.
6. Measure the voltage between C-30 harness side connector terminal No. 61 or 62 body ground.
Voltage should measure 9 volts or more.
Q: Is the measured voltage within the specified range?
YES : Erase the data link connector memory, and check the diagnostic trouble code. If DTC B210D set, replace the SRS-ECU. Then go to Step 12.
NO : Go to Step 7.
STEP 7. Check the harness for open circuit between SRS-ECU connector C-30 (terminal No. 61 or 62) and the ETACS-ECU connector C-313 (terminal No.4 or 2).
Q: Is the harness wire between SRS-ECU connector C-30 (terminal No.61 or 62) and the ETACS-ECU connector C-313 (terminal No.4 or 2) in good condition?
YES : Go to Step 12.
NO : Replace the harness wire between SRS-ECU connector C-30 and the ETACS-ECU connector C-313. Then go to Step 12.
STEP 8. 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 12.
NO : It is possible that the circuit using fuse No.12 or 18 is shorted, go to Step 9.
STEP 9. Check the SRS-ECU power supply circuit for short circuit to ground. Measure the resistance at the ETACS-ECU connector C-313.
1. Disconnect ETACS-ECU connector C-313, 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.
2. Check for continuity between terminal No. 2 or 4 and body ground. It should be an open circuit.
Q: Does continuity exist?
YES : Check the other circuit, which flows through fuse No.12 or 18. Then go to Step 12.
NO : Go to Step 10.
STEP 10. Check the power supply circuit for short circuit to ground. Measure the resistance at the SRS-ECU connector C-30.
1. Disconnect SRS-ECU connector C-30, and measure at the wiring harness side.
2. While pushing the part "A" indicated in the figure of the harness side connector, turn the lock lever to the direction of the arrow to release the lock lever, and disconnect the C-30 SRS-ECU connector.
CAUTION: Do not insert a test probe into the terminal from its front side directly as the connector contact pressure may be weakened.
3. Check for continuity between terminal No.61 or 62 and body ground. It should be an open circuit.
Q: Does continuity exist?
YES : Go to Step 11.
NO : Erase the diagnostic trouble code memory, and check the diagnostic trouble code. If DTC B210D sets, replace the SRS-ECU Then go to STEP 12.
STEP 11. Check the harness for short circuit to ground between SRS-ECU connector C-30 (terminal No.61 or 62) and ETACS-ECU connector C-313 (terminal No.4 or 2).
Q: Is the harness wire between SRS-ECU connector C-30 (terminal No.61 or 62) and ETACS-ECU connector C-313 (terminal No.4 or2) in good condition?
YES : Go to Step 12.
NO : Replace the harness wire between SRS-ECU connector C-30 and ETACS-ECU connector C-313. Then go to Step 12.
STEP 12. Recheck for diagnostic trouble code.
Check again if the DTC is set.
1. Erase the DTC.
2. Turn the ignition switch to the "ON" position.
3. Check if the DTC is set.
4. Turn the ignition switch to the "LOCK" (OFF) position.
Q: Is DTC B210D set?
YES : Return to Step 1.
NO : The procedure is complete.