Vehicles Without A/C

DTC B1018: Temperature Control Dial SW Error [Vehicles without A/C]










DTC SET CONDITION

DTC B1018 will be set when the heater control module cannot receive the signal of temperature adjustment knob.

TECHNICAL DESCRIPTION (COMMENT)

Current trouble

- The heater control module, the heater control panel, or connector(s) or wiring between the two may be defective.

Past trouble

- If DTC B1018 is stored as a past trouble, carry out diagnosis with particular emphasis on wiring and connector(s) between the heater control module and the heater control panel. If the connectors and wiring are normal, and obviously the ECU is the cause of the trouble, replace the ECU. If in doubt, do not replace the ECU.

TROUBLESHOOTING HINT

- Malfunction of connector.
- Malfunction of the harness.
- Malfunction of the heater control panel.
- Malfunction of the heater control module.

DIAGNOSIS

Required Special Tool:

- 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


STEP 1. Using scan tool MB991958, diagnose the CAN bus line





(1)
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.

Connect scan tool MB991958. Refer to "How to connect the Scan Tool (M.U.T.-III) Scan Tool Testing and Procedures."
(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 2.

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

STEP 2. Recheck for diagnostic trouble code.

Recheck if the DTC is set.

(1)Erase the DTC.

(2)Turn the ignition switch to "ON" position.

(3)Check if the DTC is set.

Q. Is the DTC set?

YES Go to Step 3.
NO It can be assumed that this malfunction is intermittent. How to Cope With Intermittent Malfunctions.
STEP 3. Check heater control panel connector C-138 and heater control module connector C-53 for loose, corroded or damaged terminals, or terminals pushed back in the connector.

Q. Are heater control panel connector C-138 and heater control module connector C-53 in good condition?

YES Go to Step 4.
NO Repair or replace the connector. Harness Connector Inspection.
STEP 4. Check the wiring harness between heater control module connector C-53 (terminal 9) and heater control panel connector C-138 (terminal 9).

- Check the heater control panel signal line for open and short circuit.

Q. Is the wiring harness between heater control module connector C-53 (terminal 9) and heater control panel connector C-138 (terminal 9) in good condition?

YES Go to Step 5.
NO Repair the wiring harness.
STEP 5. Recheck for diagnostic trouble code.

Recheck if the DTC is set.

(1)Erase the DTC.

(2)Turn the ignition switch to "ON" position.

(3)Check if the DTC is set.

Q. Is the DTC set?

YES Replace the heater control panel. Then go to Step 6.
NO It can be assumed that this malfunction is intermittent. How to Cope With Intermittent Malfunctions.
STEP 6. Recheck for diagnostic trouble code.

Recheck if the DTC is set.

(1)Erase the DTC.

(2)Turn the ignition switch to "ON" position.

(3)Check if the DTC is set.

Q. Is the DTC set?

YES Replace the heater control module.
NO It can be assumed that this malfunction is intermittent. How to Cope With Intermittent Malfunctions.