ABS

DTC C1860/C1861: Power Supply High Voltage/Power Supply Low Voltage

ABS-ECU Power Supply And Ground Circuit Connector: A-02, C-24:

Connectors: C-202, C-203, C-308:

CAUTION: If there is any problem in the CAN bus lines, an incorrect diagnostic trouble code may be set. Prior to this diagnosis, diagnose the CAN bus lines. Refer to Diagnostic Trouble code diagnosis.

CIRCUIT OPERATION
The ABS-ECU is energized by the ignition switch (IG1) through multi-purpose fuse 23 and the ABS-ECU terminal 20.

ABS DTC SET CONDITIONS
^ C1861 will be set when the power supply voltage to the ABS-ECU has decreased to a predetermined value or lower.
^ C1860 will be set when the power supply voltage to the ABS-ECU has increased to a predetermined value or higher.

TROUBLESHOOTING HINTS (THE MOST LIKELY CAUSES FOR THESE DTCs ARE TO SET ARE:)

Correct trouble
^ Excessive electrical load
^ Defective battery
^ Damaged wiring harness or connector
^ Malfunction of the hydraulic unit (integrated with ABS-ECU)
^ Charging system failed

PAST TROUBLE
Carry out diagnosis with particular emphasis on connector(s) or wiring harness in the power supply circuit (terminal 7) to the ABS-ECU. For diagnosis procedures, refer to "How to treat past trouble".

DIAGNOSIS

Required Special Tools:
^ MB991958: Scan Tool (M.U.T.-III Sub Assembly)
^ MB991824: V.C.I.
^ MB991827: M.U.T.-III USB Cable
^ MB991910: M.U.T.-III Main Harness A
^ MB991974: ABS Check Harness

STEP 1. 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 to the data link connector.
(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 Diagnosis. Then go to Step 2.

STEP 2. Recheck for diagnostic trouble code.

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) Turn the ignition switch to the "ON" position.
(2) Erase the DTC.
(3) Turn the ignition switch to the "LOCK" (OFF) position.
(4) Turn the ignition switch to the "ON" position.
(5) Check if the DTC is set.
(6) Turn the ignition switch to the "LOCK" (OFF) position.
Q: Is DTC C1860 or C1861 set?
YES: Go to Step 3.
NO: The procedure is complete.

STEP 3. Check the battery.
Check the battery, refer to Battery test.
Q: Is the battery in good condition?
YES: Go to Step 4.
NO: Charge or replace the battery. Then go to Step 8.

STEP 4. Check the charging system.
Check the charging system, refer to Charging system diagnosis.
Q: Is the charging system in good condition?
YES: Go to Step 5.
NO: Repair or replace the charging system component(s). Then go to Step 8.

STEP 5. Measure the voltage at ABS-ECU connector A-02.

(1) Disconnect the connector A-02, and connect special tool MB991974 to the wiring harness-side connector.

NOTE: Do not connect special tool MB991974 to the ABS-ECU.

(2) Turn the ignition switch to the "ON" position.
(3) Measure the voltage between terminal 7 and ground. It should be approximately 12 volts (battery positive voltage).
Q: Is the voltage approximately 12 volts (battery positive voltage)?
YES: Go to Step 7.
NO: Go to Step 6.

STEP 6. Check ABS-ECU connector A-02, intermediate connector C-24, junction block connectors C-202, C-203 and ignition switch connector C-318 for loose, corroded or damaged terminals, or terminals pushed back in the connector.

^ ABS-ECU connector A-02

^ Intermediate connector C-24

^ Junction block connectors C-202 and C-203

^ Ignition switch connector C-308

Q: Are the connectors and terminals in good condition?
YES: An open or short circuit may be present in the power supply line to the ABS-ECU. Repair the wiring harness between ABS-ECU connector A-02 terminal 7 and ignition switch connector C-308 terminal 4. Go to Step 8.
NO: Repair or replace the damaged component(s). Refer to Harness Connector Inspection. Then go to Step 8.

STEP 7. Recheck for diagnostic trouble code.

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. Check again if the DTC is set.

(1) Turn the ignition switch to the "ON" position.
(2) Erase the DTC.
(3) Turn the ignition switch to the "LOCK" (OFF) position.
(4) Turn the ignition switch to the "ON" position.
(5) Check if the DTC is set.
(6) Turn the ignition switch to the "LOCK" (OFF) position.
Q: Is DTC C1860 or C1861 set?
YES: Replace the hydraulic unit (integrated with ABS-ECU). Then go to Step 8.
NO: It can be assumed that this malfunction is intermittent. Refer to How to Use Troubleshooting/Inspection Service Points - How to Cope with Intermittent Malfunction.

STEP 8. Recheck for diagnostic trouble code.