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Toyota Sienna Service Manual: Identification of noise source

Toyota Sienna Service Manual / Navigation / Navigation system / Identification of noise source

1. Radio Description

  1. Radio frequency band

Radio Description

  1.  Radio broadcasts use the radio frequency bands shown in the table below
  1. Service area

Radio Description

  1. The service areas of AM and FM broadcasts are vastly different. Sometimes an AM broadcast can be received very clearly but an FM stereo cannot. FM stereo has the smallest service area, and is prone to pick up static and other types of interference such as noise.
  1.  Radio reception problems

HINT: In addition to static, other problems such as "phasing", "multipath", and "fade out" exist. These problems are not caused by electrical noise, but by the radio signal propagation method itself.

Radio Description

  1. Phasing
    AM broadcasts are susceptible to electrical interference and another kind of interference called phasing. Occurring only at night, phasing is the interference created when a vehicle receives 2 radio wave signals from the same transmitter. One signal is reflected off the ionosphere and the other signal is received directly from the transmitter.

Radio Description

  1. Multipath
    Multipath is a type of interference created when a vehicle receives 2 radio wave signals from the same transmitter. One signal is reflected off buildings or mountains and the other signal is received directly from the transmitter.

Radio Description

  1. Fade out
    Fade out is caused by objects (buildings, mountains, and other large obstacles) that deflect away part of a signal, resulting in a weaker signal when the object is between the transmitter and vehicle. High frequency radio waves, such as FM broadcasts, are easily deflected by obstructions. Low frequency radio waves, such as AM broadcasts, are much more difficult to deflect.
  1.  Noise problem
    Technicians must have a clear understanding about each customer's noise complaint. Use the following table to diagnose noise problems.

Radio Frequency

Noise Occurrence Condition

Presumable Cause

AM Noise occurs in a specified area Foreign noise
AM Noise occurs when listening to an intermittent broadcast An identical program transmitted from multiple towers can cause noise where the signals overlap
AM Noise occurs only at night Music beat from a distant broadcast
FM Noise occurs while driving in a specified area Multipath or phasing noise resulting from a change in FM frequency

HINT: If the noise does not match the examples above, refer to the descriptions about phasing and multipath.

How to proceed with troubleshooting
1 VEHICLE BROUGHT INTO A WORKSHOP 2 DIAGNOSTIC QUESTIONING AND SYMPTOM CONFIRMATION Ask the customer about symptoms and confirm malfunctions. 3 CONFIRM THE SYSTEM NORMAL CONDITION 4 CHECK D ...

System normal condition check
1. CHECK NORMAL CONDITION  If the symptom is applicable to any of the following, it is intended behavior, and not a malfunction. Symptom Answer A longer route ...

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