B1551

DTC B1551: Serial Communication Circuit Malfunction

Wiring Diagram










DTC Detecting Condition and Trouble Area






DTC Troubleshooting



1.
Was "Air Conditioning System Check" performed?
YES
Go to Step 2.
NO
Go to Air Conditioning System Check:Auto A/C.

2. Backup power supply circuit fuse check

Check backup power supply circuit fuse for blowing.

Is fuse(s) blown?
YES
Replace blown fuse and check for short in backup power supply circuit.
NO
Go to Step 3.

3. Wire harness check

Turn ignition switch to OFF position.
Disconnect connectors from BCM and HVAC control module.
Check for proper connection to serial communication circuit terminal of BCM and HVAC control module connectors.
If OK, check that serial communication circuit is as follows.
- Wiring harness resistance of serial communication circuit is less than 3 ohms
- Insulation resistance between serial communication circuit terminal and vehicle body ground is Infinity
- Circuit voltage of serial communication circuit is 0 - 1 V with ignition switch turned ON

Are they in good condition?
YES
Go to Step 4.
NO
Serial communication circuit is open, short or high resistance.

4. Communication data check

Connect connectors to BCM and HVAC control module with ignition switch turned OFF.
Check that serial communication signal is output from BCM referring to "Voltage Check" under Inspection of BCM and Its Circuits Inspection of BCM and Its Circuits.

Is serial communication signal output?
YES
Substitute a known-good HVAC control module and recheck.
NO
Substitute a known-good BCM and recheck.