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DTC Troubleshooting: B120A (I-B4), B120A (8A)
DTC B120A or DTC screen I-B4 or DTC indicator 8A: Climate Control Unit LIN Communication Bus Line Error
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DTC Description |
DTC |
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B120A Climate Control Unit LIN Communication Bus Line Error |
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1. |
Problem verification:
Problem verification
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?1. |
Clear the DTCs with the HDS.
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?2. |
Turn the vehicle to the OFF (LOCK) mode and then the ON mode. |
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?4. |
Check for DTCs.
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DTC Description |
DTC |
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B120A Climate Control Unit LIN Communication Bus Line Error |
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Is DTC B120A or Error on the DTC screen I-B4 (climate control panel without display) or 8A (climate control panel with display) indicated?
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Intermittent failure. Check for loose wires or poor connections on the climate control panel circuit.? |
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2. |
Fuse check:
Fuse check
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?1. |
Turn the vehicle to the OFF (LOCK) mode. |
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?2. |
Check the following fuse.
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Fuse |
No. D9 (10 A) |
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Location |
Under-dash fuse/relay box | |
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Is the fuse OK?
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Replace the fuse, and recheck. If the fuse blows again, repair a short in the No. D9 (10 A) fuse circuit.? |
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3. |
Determine possible failure area (BUS-DATA line, others):
Determine possible failure area (BUS-DATA line, others)
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?1. |
Disconnect the following connector.
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Climate control panel 20P connector | |
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?2. |
Turn the vehicle to the ON mode. |
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?3. |
Measure the voltage between test points 1 and 2.
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Test condition |
Vehicle ON mode |
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Climate control panel 20P connector: disconnected |
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Test point 1 |
Climate control panel 20P connector (female terminals) No. 13:  |
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Test point 2 |
Climate control panel 20P connector (female terminals) No. 19:  | |
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Is there battery voltage?
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4. |
Shorted wire check (BUS-DATA line):
Shorted wire check (BUS-DATA line)
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?1. |
Turn the vehicle to the OFF (LOCK) mode. |
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?2. |
Disconnect the following connector.
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Climate control unit connector A (32P) | |
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?3. |
Check for continuity between test points 1 and 2.
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Test condition |
Vehicle OFF (LOCK) mode |
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Climate control unit connector A (32P): disconnected |
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Climate control panel 20P connector: disconnected |
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Test point 1 |
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Test point 2 |
Body ground | |
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Is there continuity?
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Repair a short to ground in the BUS-DATA wire.? |
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The BUS-DATA wire is not shorted. Go to step 5. |
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5. |
Open wire check (BUS-DATA line):
Open wire check (BUS-DATA line)
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?1. |
Check for continuity between test points 1 and 2.
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Test condition |
Vehicle OFF (LOCK) mode |
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Climate control unit connector A (32P): disconnected |
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Climate control panel 20P connector: disconnected |
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Test point 1 |
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Test point 2 |
Climate control panel 20P connector (female terminals) No. 18:  | |
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Is there continuity?
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The BUS-DATA wire is not open. Go to step 6. |
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Repair an open in the BUS-DATA wire.? |
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6. |
Climate control panel check (substitution):
Climate control panel check (substitution)
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?1. |
Reconnect the following connector.
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Climate control unit connector A (32P) | |
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?3. |
Clear the DTCs with the HDS. |
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?4. |
Turn the vehicle to the OFF (LOCK) mode and then the ON mode. |
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?6. |
Check for DTCs.
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DTC Description |
DTC |
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B120A Climate Control Unit LIN Communication Bus Line Error |
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Is DTC B120A or Error on the DTC screen I-B4 (climate control panel without display) or 8A (climate control panel with display) indicated?
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7. |
Open wire check (IG2 A/C line):
Open wire check (IG2 A/C line)
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?1. |
Measure the voltage between test points 1 and 2.
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Test condition |
Vehicle ON mode |
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Climate control panel 20P connector: disconnected |
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Test point 1 |
Climate control panel 20P connector (female terminals) No. 19:  |
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Test point 2 |
Body ground | |
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Is there battery voltage?
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Check for an open in the GND wire. If the wire is OK, check for poor ground at G402.? |
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Repair an open in the IG2 A/C wire.? | |