Code No.B2421 Radio tuner

caution

If there is any problem in the CAN bus lines, an incorrect diagnosis code may be set. Prior to this diagnosis, always diagnose the CAN bus lines.
Before replacing the audio unit, be sure to check that the power supply circuit, earth circuit, and communication circuit are normal.

TROUBLE JUDGMENT

If the communication cannot be established consecutively for 10 times between the incorporated tuner of audio unit and the microcomputer, the diagnosis code is set.

COMMENTS ON TROUBLE SYMPTOM

The audio unit or CAN bus line may have a problem.

PROBABLE CAUSES

Malfunctions of audio unit
Malfunction of CAN bus line wiring harness and connector

DIAGNOSIS PROCEDURE

STEP 1. M.U.T.-III CAN bus diagnostics

Use the M.U.T.-III to diagnose the CAN bus lines.

Q. Is the check result normal?

	Go to Step 2.

	Repair the CAN bus line (Refer to GROUP 54C - Troubleshooting ).

STEP 2. Check whether the diagnosis code is reset.

Check again if the diagnosis code is set to the audio unit.

(1)Erase the diagnosis code.

(2)Turn the ignition switch from "LOCK" (OFF) position to "ON" position.

(3)Check if diagnosis code is set.

Q. Is the diagnosis code set?

	Replace the audio unit.

	The trouble can be an intermittent malfunction (Refer to GROUP 00 - How to use Troubleshooting/inspection Service Points - How to Cope with Intermittent Malfunction ).