Control Panel Communication Error [Vehicles Without A/C]
DTC B1000: Control panel communication error [Vehicles without A/C]Heater Control Panel Circuit:
DTC SET CONDITION
DTC B1000 will be set when the communication between heater control unit and heater control panel cannot be per- formed.
TECHNICAL DESCRIPTION (COMMENT)
Current trouble
- The heater control unit, the heater control panel, or connector(s) or wiring between the two may be defective.
Past trouble
- If DTC B1000 is stored as a past trouble, carry out diagnosis with particular emphasis on wiring and connector(s) between the heater control unit 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 unit.
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.
Use scan tool MB991958 to diagnose the CAN bus lines.
1 Connect scan tool MB991958 to the data link connector.
2 Turn the ignition switch to "ON" position.
3. Diagnose the CAN bus line.
Q: Is the check result satisfactory?
YES : Go to Step 2.
NO : Repair the CAN bus lines.
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.
STEP 3. Check heater control panel connector C-136 for loose, corroded or damaged terminals, or terminals pushed back in the connector.
Q: Is heater control panel connector C-136 in good condition?
YES : Go to Step 4.
NO : Repair or replace the connector
STEP 4. Measure the voltage at heater control panel connector C-136.
1. Disconnect heater control panel connector C-136, and measure the voltage at the harness side.
2. Turn the ignition switch to the "ON" position.
3. Measure the voltage between terminal 6 and ground.
- The measured value should be approximately 12 volts (battery positive voltage).
Q: Is the measured voltage approximately 12 volts?
YES : Go to Step 6.
NO : Go to Step 5.
STEP 5. Check the wiring harness between heater control panel connector C-136 (terminal 6) and ETACS-ECU connector C-317 (terminal 5).
- Check the heater control panel power supply line for open circuit.
Q: s the wiring harness between heater control panel connector C-136 (terminal 6) and ETACS-ECU connector C-317 (terminal 5) in good condition?
YES : It can be assumed that this malfunction is intermittent.
NO : Repair the wiring harness.
STEP 6. Measure the resistance at heater control panel connector C-136.
1. Disconnect heater control panel connector C-136, and measure the resistance at the wiring harness side.
2. Measure the resistance value between terminal 7 and ground.
- The measured value should be 2 ohms or less.
Q: Does the measured resistance value correspond with his range?
YES : Go to Step 8.
NO : Go to Step 7.
STEP 7. Check the wiring harness between heater control panel connector C-136 (terminal 7) and ground.
- Check the heater control panel ground line for open circuit.
Q: Is the wiring harness between heater control panel connector C-136 (terminal 7) and ground in good condition?
YES : It can be assumed that this malfunction is intermittent.
NO : Repair the wiring harness.
STEP 8. Check heater control unit connector C-48 for loose, corroded or damaged terminals, or terminals pushed back in the connector.
Q: Is heater control unit connector C-48 in good condition?
YES : Go to Step 9.
NO : Repair or replace the connector.
STEP 9. Check the wiring harness between heater control unit connector C-48 (terminal 9) and heater control panel connector C-136 (terminal 9).
- Check the heater control panel signal line and ground line for open and short circuit.
Q: s the wiring harness between heater control unit connector C-48 (terminal 9) and heater control panel connector C-136 (terminal 9) in good condition?
YES : Go to Step 10.
NO : Repair the wiring harness.
STEP 10. 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 11.
NO : It can be assumed that this malfunction is intermittent.
STEP 11. 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 unit.
NO : It can be assumed that this malfunction is intermittent.