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

id0903e3804400

2 | Noise from radio (AM only)
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Possible DTC | Using the M-MDS | U3000:04
Without using M-MDS (On-board diagnostic test mode) | 09:Er22
Possible cause | • Jamming from aftermarket electronic equipment (two-way radio, navigation system, mobile phone, etc.) • Battery malfunction • Noise from electrical system on vehicle (e.g. fuel pump) • Charging system malfunction • Electronic jamming from outside, or inferior condition of broadcasting station radio wave • Antenna plug poor connection • Antenna feeder malfunction • Antenna installation loosened • Audio unit malfunction

Diagnostic procedure

STEP | INSPECTION | ACTION
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1 | • Can the location where the noise occurs be specified? | Yes | The system is normal. (Explain to the customer that the noise is caused by radio wave disturbances or broadcast wave conditions from the outside.)
No | Go to the next step.
2 | • Tune to local broadcasting station and check reception condition. • Is reception okay? | Yes | Tune to correct frequency of broadcasting station. If not preset, preset it.
No | Go to the next step.
3 | • Is aftermarket electronic equipment (two-way radio, navigation system, mobile phone, etc.) installed? Note • TV antenna located closely to audio antenna can be cause of noise. Relocate TV antenna. | Yes | Go to the next step.
No | Go to Step 5.
4 | • Remove aftermarket electronic equipment. • Turn audio unit ON and check reception condition. • Is reception improved? | Yes | The system is normal. (Explain to customers that aftermarket electronic equipment is cause of noise)
No | Go to the next step.
5 | • Measure battery voltage. • Is battery voltage okay? Specification: With ignition switch ON: 11.5 V or more At idling: 12.5 V or more Note • Inspect that battery cables are connected to terminals securely. | Yes | Go to the next step.
No | Charge battery. Inspect charging system, and repair or replace if necessary.
6 | • Is noise occurring only when vehicle electrical system (e.g. fuel pump) operates? Note • Identify subject electrical component by disconnecting fuse, turning switch ON & OFF, or disconnecting & connecting connector. • It will be easy when simulation function on M-MDS is used. | Yes | Go to the next step.
No | Go to Step 8.
7 | • Inspect power supply, ground condition, and noise prevention capacitor for electrical component. • Is noise present after inspection? Note • Inspect 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 etc. | Yes | Go to the next step.
No | Troubleshooting completed. Note • The audio unit supplies 12 V battery power to the antenna amplifier for the AM radio reception in the radio mode. The audio unit cannot receive the AM signals without the 12 V battery power to the antenna amplifier. If the AM signals become strong, the audio/unit car-navigation unit may receive the signal with noises.
8 | • Inspect antenna plug connection condition. • Is connection okay? | Yes | Go to the next step.
No | Insert antenna plug securely.
9 | • Turn the ignition switch to the OFF position. • Measure continuity between antenna feeder axis and ground. • Is there any continuity? | Yes | Replace antenna feeder.
No | Go to the next step.
10 | • Compare reception with other audio unit on same model (model/unit) under same problem conditions. • Is reception equivalent between customer’s unit and compared unit? Note • Due to following differences, you may feel difference in reception efficiency. (Vehicle side factor) ― Antenna installation location, height, feeder wiring routing, optional electrical equipment (Audio unit factor) ― Volume concern type: It decreases change of volume when signals become weak. (Noise is easily noticed) ― Noise decrease type: It decreases volume when signals become weak, so that noise is not noticeable. | Yes | The system is normal (It is caused by electronic jamming from outside, or inferior broadcasting station signal condition).
No | Replace audio unit. (See AUDIO UNIT REMOVAL/INSTALLATION.)