Code No.18: Ignition switch circuit B open (open circuit or short circuit)








caution If the battery voltage drops or rises while making this check, Diagnosis code No.16 is set as an existing problem, making it impossible to perform correct trouble diagnosis. Before carrying out the following diagnosis, test the battery and charge it if necessary.

OPERATION


The ABS-ECU has two power supply lines. One of the lines supplies the power to the ABS-ECU terminal No. 31 from the ignition switch (IG2) through fuse No. 22. Another line supplies the power to the ABS-ECU terminal No. 13 from the ignition switch (IG2) through the fuse No. 12 in the junction block and through joint connectors (4) and (5).

DIAGNOSIS CODE SET CONDITIONS


The diagnosis code is set if the ABS-ECU power supply circuit {ignition switch (IG2) to ABS-ECU terminal No. 31{ is open or short, or if the ABS-ECU internal circuit malfunction occurs.

PROBABLE CAUSES



DIAGNOSIS

STEP 1. Check ABS-ECU connector D-250 for loose, corroded or damaged terminals, or terminals pushed back in the connector.

Q. Is the check result normal?
Go to Step 2.
Repair or replace it. Then go to Step 5.

STEP 2. Check the power supply circuit at ABS-ECU harness connector D-250.

  • Disconnect ABS-ECU connector D-250 and measure at the harness connector (harness side).
  • Start the engine.
  • Measure the voltage between terminal 31 and body earth.
OK: Approx. 12 volts (battery positive voltage)

Q. Is battery positive voltage (approx. 12 volts) present?
Go to Step 5.
Go to Step 3.

STEP 3. Check intermediate connector D-231 for loose, corroded or damaged terminals, or terminals pushed back in the connector.

Q. Is the check result normal?
Go to Step 4.
Repair or replace it. Then go to Step 5.

STEP 4. Check the harness wires between ABS-ECU connector D-250 (terminal 31) and ignition switch (IG2).

Q. Is the check result normal?
Go to Step 5.
Repair or replace it. Then go to Step 5.

STEP 5. Recheck for diagnosis code.
(1)Erase the diagnosis code.
(2)Recheck for diagnosis code.

Q. Is code No.18 set?
Replace the ABS-ECU (Refer to GROUP 35B, ABS Control Unit ).
The procedure is complete.