B2798

ENGINE IMMOBILISER: ENGINE IMMOBILISER SYSTEM (w/o Smart Key System): B2796,B2798: No Communication in Immobiliser System
B2798 - Communication Malfunction No. 2

DESCRIPTION

When a key is inserted into the ignition key cylinder but no communication occurs between the key and transponder key ECU, DTC B2796 is output. When a key is inserted into the ignition key cylinder but a communication error occurs between the key and transponder key ECU, DTC B2798 is output.





WIRING DIAGRAM





INSPECTION PROCEDURE

PROCEDURE

1. READ VALUE USING TECHSTREAM (ENGINE IMMOBILISER SYSTEM)

(a) Connect the Techstream to the DLC3.

(b) Turn the ignition switch ON with a key that cannot start the engine.

(c) On the Techstream, enter the following menus: Body Electrical / Immobiliser / Data List / Immobiliser. Read the result.

Immobiliser:





OK:

Unset (key is in ignition key cylinder) appears on the screen.

NG -- CHECK WHETHER ENGINE STARTS WITH OTHER KEY

OK -- REPLACE TRANSPONDER KEY ECU Removal

2. CHECK WHETHER ENGINE STARTS WITH OTHER KEY

(a) Check whether the engine starts with the vehicle's other keys.

OK:

Engine starts.

NG -- REREGISTER OR REPLACE KEY THAT CANNOT START ENGINE
OK -- Continue to next step.

3. READ VALUE USING TECHSTREAM (TRANSPONDER KEY COIL)

(a) Connect the Techstream to the DLC3.

(b) Turn the ignition switch ON with a key that cannot start the engine.

(c) On the Techstream, enter the following menus: Body Electrical / Immobiliser / Data List / Antenna Coil Status. Read the result.

Immobiliser:





OK:

Normal (Transponder key coil is normal) appears on the screen.

NG -- CHECK HARNESS AND CONNECTOR (TRANSPONDER KEY ECU - TRANSPONDER KEY AMPLIFIER)

OK -- REPLACE TRANSPONDER KEY ECU Removal

4. CHECK HARNESS AND CONNECTOR (TRANSPONDER KEY ECU - TRANSPONDER KEY AMPLIFIER)





(a) Disconnect the E46 ECU connector.

(b) Disconnect the E5 amplifier connector.

(c) Measure the resistance of the wire harness side connectors.

Standard Resistance:





NG -- REPAIR OR REPLACE HARNESS OR CONNECTOR
OK -- Continue to next step.

5. CHECK TRANSPONDER KEY AMPLIFIER (OPERATION)

(a) Temporarily replace the transponder key amplifier with a new or normally functioning one Removal.

(b) Check that the engine starts normally.

OK:

Engine starts normally.

NG -- REPLACE TRANSPONDER KEY ECU Removal

OK -- END (TRANSPONDER KEY AMPLIFIER IS DEFECTIVE)