Electronic Control

DTC C2100: Abnormal battery voltage (Too low)





CAUTION: If there is any problem in the CAN bus lines, an incorrect DTC may be set. Prior to this diagnosis, always diagnose the CAN bus lines.

OPERATION
AWD-ECU detects a power supply voltage abnormal drop, and if any abnormality occurs, it interrupts the system.

DTC SET CONDITIONS
If the following conditions are met when the system is activated, AWD-ECU gradually switches the control from AWD to FWD, flashes the AWD/LOCK indicators alternately, and sets the DTC No. C2100.

^ IG1 voltage: Less than 8 V
^ Voltage between the battery and ETACS-ECU: Less than 8 V
^ Engine speed: more than 1500 r/min

TROUBLESHOOTING HINTS

Current trouble
^ Damaged wiring harness and connectors
- Short to earth or open circuit between the battery and AWD-ECU

Past trouble
^ Intermittent wiring harness or connector failure

NOTE: For diagnosis procedures, refer to "How to treat past trouble".

DIAGNOSIS
^ MB991958: Scan Tool (M.U.T.-III Sub Assembly)
^ MB991824: Vehicle Communication Interface
^ MB991827: M.U.T.-III USB Cable
^ MB991910: M.U.T.-III Main Harness A

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. Voltage measurement 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 earth.

OK: Battery voltage

Q:Is the check result normal?
YES: Go to Step 11.
NO: Go to Step 3.

STEP 3. Wiring harness check
Check the wiring harness between the battery and the C-309 ETACS-ECU connector for damage or other problem.

Q:Is the wiring harness in good condition?
YES: Go to Step 4.
NO: Repair damage or other problem in the wiring harness. Then go to Step 11.

STEP 4. Scan tool MB991958 CAN bus diagnostics
Use scan tool MB991958 to diagnose the CAN bus lines.

Q:Is the check result normal?
YES: Go to Step 6.
NO: Repair the CAN bus line. On completion, go to Step 5.

STEP 5. Check whether the DTC is reset after repairing the CAN bus line.
(1) Erase the DTC.
(2) Turn the ignition switch from the LOCK (OFF) position to the ON position.
(3) Start the engine, and continue to run at 1500 r/min or more.
(4) Check if the DTC is set.

Q:Is the DTC No. C2100 set?
YES: Go to Step 6.
NO: This diagnosis is complete.

STEP 6. Check the following connector:
Check the connectors below for improper engagement, terminal damage or terminal drawn in the connector case.

^ C-128 AWD-ECU connector
^ C-309, C-315 ETACS-ECU connector
^ C-31 intermediate connector

Q:Are the connectors and terminals in good condition?
YES: Go to Step 7.
NO: Repair the connector(s) or terminal(s). Then go to Step 11.

STEP 7. Wiring harness check
Check the wiring harness between the C-128 AWD-ECU connector and the C-315 ETACS-ECU connector for damage or other problem.

Q:Is the wiring harness in good condition?
YES: Go to Step 8.
NO: Repair damage or other problem in the wiring harness. Then go to Step 11.

STEP 8. Voltage measurement at the AWD-ECU connector
(1) Disconnect the C-128 AWD-ECU connector.
(2) Measure the voltage between the C-128 wiring harness side connector terminals No. 4 (Ignition switch "ON") and No. 10.

OK: Battery voltage

Q:Is the check result normal?
YES: Go to Step 9.
NO: Go to Step 11.

STEP 9. Wiring harness check
Check the wiring harness between the C-128 AWD-ECU connector (terminal No. 4) and the C-309 ETACS-ECU connector (terminal No. 1) for damage or other problem.

Q:Is the wiring harness in good condition?
YES: Go to Step 10.
NO: Repair the wiring harness. Then go to Step 11.

STEP 10. Check whether the DTC is reset.
(1) Erase the DTC.
(2) Turn the ignition switch from the LOCK (OFF) position to the ON position.
(3) Start the engine, and continue to run at 1500 r/min or more.
(4) Check if the DTC is set.

Q:Is the DTC No. C2100 set?
YES: Replace AWD-ECU. Then go to Step 11.
NO: The trouble can be an intermittent malfunction.

STEP 11. Check whether the DTC is reset.
(1) Erase the DTC.
(2) Turn the ignition switch from the LOCK (OFF) position to the ON position.
(3) Start the engine, and continue to run at 1500 r/min or more.
(4) Check if the DTC is set.

Q:Is the DTC No. C2100 set?
YES: Diagnose again from Step 1.
NO: This diagnosis is complete.