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2008 - MX-5 - Body and Accessories

NO.2 NOISE FROM RADIO (AM ONLY) [AUDIO]



2

Noise from radio (am only) / Possible DTC: 09:Er22

POSSIBLE CAUSE

  • Antenna rod is not installed (standard part)

  • Jamming from aftermarket electronic equipment (two-way radio, navigation system, mobile phone, etc.)

  • Noise from electrical system on vehicle (e.g. fuel pump)

  • Battery malfunction

  • Charging system malfunction

  • Audio unit malfunction

  • Poor connection of antenna feeder plug

  • Antenna feeder malfunction

  • Open or short circuit in wiring harness between audio unit and manual antenna (antenna amplifier power supply system)

  • Electronic jamming from outside, or inferior condition of broadcasting station radio wave

  • Antenna installation loosened


Diagnostic procedure

STEP

INSPECTION

ACTION

1

  • Tune to a local broadcasting station and check the reception condition.

  • Is the reception normal?

Yes

Tune to the correct frequency for the broadcasting station.

If not preset, preset it.

No

Go to the next step.

2

  • Inspect the antenna rod condition.

  • Is the antenna rod installed?

Yes

Go to the next step.

No

Advise the customer to install the antenna rod when the radio is used.

(It the antenna rod is not a standard part, replace it.)

3

  • Is aftermarket electronic equipment (two-way radio, navigation system, mobile phone, etc.) installed?

NOTE:

  • A TV antenna located close to the audio antenna can be the cause of noise. Relocate the TV antenna.

Yes

Go to the next step.

No

Go to Step 5.

4

  • Remove aftermarket electronic equipment.

  • Turn the audio unit on and check the reception condition.

  • Does reception improve?

Yes

The system is normal. (Explain to the customer that aftermarket electronic equipment is the cause of the noise)

No

Go to the next step.

5

  • Measure the battery voltage.

  • Is battery voltage normal?

    Standard
  • With ignition switch ON: 11.5 V or more

  • At idling: 12.5 V or more

NOTE:

  • Verify that the battery cables are connected to the terminals securely.

Yes

Go to the next step.

No

Charge the battery. Inspect the charging system, and repair or replace if necessary.

6

  • Does the noise occur only when the vehicle electrical system (e.g. fuel pump) operates?

NOTE:

  • Identify the suspect electrical component by disconnecting fuses, turning switches on & off, or disconnecting and connecting connectors.

  • It is easier to use the simulation function on the M-MDS.

Yes

Go to the next step.

No

Go to Step 8.

7

  • Verify the condition of the power supply and ground of the electric components, and the noise prevention capacitor.

  • Is noise present after the inspection?

NOTE:

  • Inspect the following:

    • Power supply to electrical component for voltage drop (compare with battery voltage)

    • Resistance between ground of electrical component and body. (Should be close to 0 ohm)

    • Installation condition of noise prevention capacitor for fuel pump.

Yes

Go to the next step.

No

Troubleshooting completed.

NOTE:

  • The audio unit supplies 12 V battery power to the antenna amplifier for AM radio reception in the radio mode. The audio unit cannot receive AM signals without the 12 V battery power to the antenna amplifier. If the AM signals strengthen, the audio unit may receive the signals with noise.

8

  • Inspect the antenna feeder plug connection condition.

  • Is the connection normal?

Yes

Go to the next step.

No

Insert the antenna feeder plug securely.

9

  • Turn the ignition switch to the LOCK position.

  • Measure the continuity between the antenna the feeder axis and ground.

  • Is there any continuity?

Yes

Replace antenna feeder.

(See ANTENNA FEEDER LOCATION.)

No

Go to the next step.

10

  • Measure the voltage at audio unit terminal H (24-pin) to verify the antenna amplifier power supply .

  • Is the voltage B+?

Yes

Go to the next step.

No

Replace the audio unit.

(See CENTER PANEL UNIT REMOVAL/INSTALLATION.)

(See CENTER PANEL UNIT DISASSEMBLY/ASSEMBLY.)

(See AUDIO UNIT DISASSEMBLY/ASSEMBLY.)

11

  • Turn the ignition switch to the LOCK position.

  • Inspect the continuity between audio unit terminal H (24-pin) and manual antenna terminal A.

  • Is there any continuity?

Yes

Go to the next step.

No

Repair or replace the wiring harness between the audio unit and the manual antenna (antenna amplifier power supply system), then verify the reception conditon.

If the reception has improved, troubleshooting is completed.

If the reception has not improved, go to the next step.

12

Compare the reception with another audio unit on same model (model/unit) under the same problem conditions.

  • Is the reception equivalent to the customer’s unit?

NOTE:

  • Due to the following differences, you may sense a difference in reception efficiency.

    • (Vehicle factor)
    • Antenna installation location, height, feeder wiring routing, optional electrical equipment

      (Audio unit factor)
    • High-tone setting: Decreases effective volume range when signals become weak. (Noise is easy to be conspicuous)

    • Noise restraint setting: Widens effective volume range when signals become weak. (Noise is not conspicuous.)

Yes

The system is normal (It is caused by electronic jamming from outside, or inferior broadcasting station signal condition).

No

Go to the next step.

13

  • Retighten the ground for the antenna and antenna amplifier. Retighten the antenna rod.

  • Is the noise present after retightening?

Yes

Replace the audio unit.

(See CENTER PANEL UNIT REMOVAL/INSTALLATION.)

(See CENTER PANEL UNIT DISASSEMBLY/ASSEMBLY.)

(See AUDIO UNIT DISASSEMBLY/ASSEMBLY.)

No

Troubleshooting completed.




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