ABNORMAL IMMOBILIZER COMMUNICATION
(DTC CODE B2799 / DIAGNOSIS MONITOR CODE 9)

1. Insert each ID-registered key into the key cylinder and check that the starter key can be turned "ON" and the engine can start running.
   
   
   
   

   Result of activation	Step
   The engine starts running with all of the keys.	Go to YES.
   The engine does not start running with any of the keys.	Go to NO.
   The starter key can be turned "ON" and the engine starts running with only some of the keys.	Go to each diagnosis code.

   

   In case of each diagnosis code, recheck diagnosis code with the HINO-DX and troubleshoot indicated diagnosis codes.

    

NO Go to [2] Checking the diagnosis code.	YES Normal

1. Use HINO-DX to check immobilizer ECU diagnosis codes.
   
   
   
   

   

   If communication with HINO-DX fails, check a fuse and a DC/DC converter or an immobilizer power supply and a GND harness.

   Standard: No immobilizer ECU diagnosis codes must be output (DTC codes B2780, B2784 and B2793-B2798).

NO Troubleshoot indicated diagnosis codes.	YES Normal

1. Check a history of immobilizer ECU replacements.
   
   

   Standard: There must be no history of immobilizer ECU replacements. Or communication ID codes of the engine ECU and immobilizer ECU must be re-registered after immobilizer ECU replacement.

   

   • If the immobilizer ECU has been replaced, the diagnosis code (DTC code B2799 / diagnosis monitor code 9) will be indicated because communication ID codes stored in the immobilizer ECU and engine ECU are no longer the same.
   • Not replaceable with an immobilizer ECU previously installed to another vehicle.

NO Re-register communication ID codes of the engine ECU and the immobilizer ECU.	YES Proceed to [4] Measuring voltage between terminals

1. Set the starter key to the "LOCK" position and connect the signal check harness.
   

   

   ECU terminal No.	Description of terminal
   V25	Immobilizer signal
   V40	GND

   Standard value: 12-16V
2. Turn the starter key "ON" and measure voltage between the terminals V25 and V40.

NO Go to [5] Measuring resistance between terminals.	YES Go to [6] Re-registering communication ID codes.

1. Set the starter key to the "LOCK" position and disconnect the signal check harness connectors from the ECU.
2. Disconnect the immobilizer ECU connector.
3. Measure continuity between the terminal V25 and the body GND/6th terminal of the immobilizer ECU connector (vehicle harness side).
   

   

   Standard value: Below 1 Ω (between engine ECU and immobilizer ECU)10 kΩ or more (between engine ECU and body GND)

NO Disconnection or short-circuit of harness between engine ECU (IMO) and immobilizer ECU (EFII). Repair or replace the harness.	YES Proceed to [6] Re-registering communication ID codes.

1. After replacement of the engine ECU, re-register communication ID codes.

NO Immobilizer ECU failure. Take the steps as instructed below. Replace the immobilizer ECU. Re-register keys and communication ID codes. Register communication ID codes for the engine ECU and immobilizer ECU.	YES End

1. Confirm the DTC B2799 is inactive

   • Start the engine and let it idling condition.
   • Verify the DTC B2799 is inactive.

   

2. DTC Clear

   • Clear the DTC with Hino DX
   • Confirm the same DTC is not reoccurred

   

B2799 is reoccur: Return to first process Other DTC appear: Refer to concerned Trouble shooting

Complete