Supplemental Restraint System ECU

DTC B210D: Battery Abnormal Low Voltage

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 fusible link (34).
- The SRS-ECU power is supplied from two circuits. Even if one circuit is shut off, the air bag can inflate.

DTC SET CONDITIONS

The code is set when the battery voltage becomes low or when the open circuit occurs to the power supply circuit.

TROUBLESHOOTING HINTS

- Battery voltage low voltage
- Open circuit to power supply circuit
- Damaged wiring harnesses or connectors
- Malfunction of the SRS-ECU
- Malfunction of ETACS-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. Power supply fuse number 12,18 check.

Q. Is the fuse in good condition?

YES Go to Step 3.
NO Go to Step 2.
STEP 2. Wiring harness check between the C-313 ETACS-ECU connector terminal No. 4/2 and the C-30 SRS-ECU connector terminal No. 61/62.

- Short circuit check for SRS-ECU power supply wire

Q. Is the check result normal?

YES Replace the power supply fuse.
NO Repair the wiring harness. And than replace the power supply fuse.
STEP 3. Battery check.

Battery Test.

Q. Is the check result normal?

YES Go to Step 4.
NO Charge or replace the battery.
STEP 4. Measure the voltage at the ETACS-ECU connector.

(1)Disconnect the C-309 ETACS-ECU connector.

(2)Measure the voltage between the C-309 harness side connector terminal No. 1 and the body ground.

- The voltage should measure 12 volts (battery positive voltage).

Q. Is the measured voltage approximately 12 volts (battery positive voltage)?

YES Go to Step 6.

NO Go to Step 5.

STEP 5. Wiring harness check between the fusible link (34) and the C-309 ETACS-ECU connector terminal No. 1.

- Open circuit check for ETACS-ECU power supply wire

Q. Is the check result normal?

YES Go to Step 11.
NO Repair the wiring harness.
STEP 6. 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 Reading and Clearing Diagnostic Trouble Codes."
(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 8.

NO Repair the CAN bus line CAN Bus Diagnostics Chart).

STEP 8. 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 9.
NO There is an intermittent malfunction such as poor engaged connector(s) or open circuit How to Cope With Intermittent Malfunctions).
STEP 9. Check the harness for open circuit between SRS-ECU connector C-30 (terminal No.61 and 62) and the ETACS-ECU connector C-313 (terminal No.4 and 2).

(1)Disconnect the negative battery terminal.

(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.
(3)Disconnect the ETACS-ECU connector C-313.

(4)Check for continuity between the following terminals. It should be less than 2 ohms.
[Fuse No.12]

- SRS-ECU connector C-30 (terminal No.62) and the ETACS-ECU connector C-313 (terminal No.2)
[Fuse No.18]

- SRS-ECU connector C-30 (terminal No.61) and the ETACS-ECU connector C-313 (terminal No.4)

Q. Does continuity exist?

YES Go to Step 10.

NO Repair the harness wire between SRS-ECU connector C-30 and the ETACS-ECU connector C-313.

STEP 10. Measure the voltage at the C-30 SRS-ECU connector.

(1)Disconnect the negative battery terminal.

(5)Take the measurements below at the C-30 harness side connector.

- Voltage between terminal No. 61/62 and body ground
OK: 9 V or more

Q. Is the measured voltage within the specified range?

YES Go to Step 11.

NO Replace the ETACS-ECU Electronic Time and Alarm Control System (ETACS)-ECU Removal and Installation).

STEP 11. 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 Replace the SRS-ECU (Refer to Service and Repair).
NO There is an intermittent malfunction such as poor engaged connector(s) or open circuit How to Cope With Intermittent Malfunctions).