Cellular Phone - Poor Bluetooth(R) Call Quality
91 Bluetooth Phone: poor call quality
91 12 50
2026888/3
August 1, 2012.
Supersedes Technical Service Bulletin Group 91 number 11 - 21 dated October 24, 2011 for reasons listed below.
Affected Vehicles
Condition
Customer complains of one of the following during a phone call:
- Echo effects
- Driver or other party cannot hear conversation
- Sound distortion or feedback
- The sound is distorted, hisses or scrapes
Technical Background
This bulletin provides guidelines for analyzing the call quality of the Bluetooth system in the vehicle.
There are several factors affecting call quality within a vehicle:
^ Interior noises
^ The quality of a Bluetooth call is directly related to the signal to noise ratio. Items that can affect this ratio are:
Different road surfaces/tires.
Open windows or sunroof.
Climate control fan speed and vent position.
^ Body Height/Seat position
^ Variations in customer height/seat position changes the distance to the microphones and thus the reception quality.
^ Phone reception and provider
Audi A4 Quattro Sedan (8K2) L4-2.0L Turbo (CAEB) Page 95
^ Reduced reception can introduce noise into the Bluetooth call. Reception display on the phone is an indicator, but not an accurate
representation of the actual reception.
^ Phone providers introduce noise suppression into their system to increase call quality. This suppression can make the call sound thinner, and in
conjunction with high interior noises, has a compounding negative effect on the sound quality.
^ Technical issues
Production Solution
Not Applicable
Service
1. When analyzing Bluetooth call quality complaints, attempt to gather as much information as possible from the customer to aid in diagnosis.
Questions to ask are:
^ Customer phone model and current software. Verify the phone and software is compatible at www.audiusa.com/bluetooth. If the phone is
not compatible, a known compatible phone can be used for diagnosis purposes to prove the system is functioning correctly.
^ What issue is the customer experiencing with the Bluetooth call?
Echoing?
No sound? Issue experienced by driver or other person?
Sound is too quiet? Issue experienced by driver or other person?
Distorted audio? Issue experienced by driver or other person?
^ How often does the complaint occur?
^ Does there seem to be any pattern to the customer actions before the complaint occurs?
2. Depending on the complaint information provided by the customer, proceed to the appropriate step.
^ Echoing
MMI 3G/3G+:
^ Test and/or replace mobile phone.
^ System architecture does not allow for echoing to occur. Do not replace a control unit for an echoing concern.
UHV CAN, MMI 2G:
^ Reduce call volume (on the mobile phone and/or the vehicle).
^ If echoing occurs during every call, reset the phone or replace if necessary.
^ If the echoing always occurs on the same stretches of road or always when calling the same person, this can be deduced as a reception or
carrier issue and not the vehicle.
^ If echoing cannot be reduced using above methods/explanations, test and/or replace the UHV control unit.
^ No Sound
For the other person on the line:
^ Test and/or replace microphone.
^ Test and/or replace mobile phone.
^ If sound cannot be corrected using above methods/explanations, test and/or replace the UHV control unit.
For the driver:
^ Microphones do not have an effect on sound volume/quality for driver, and can be ruled out.
^ Test and/or replace mobile phone.
Audi A4 Quattro Sedan (8K2) L4-2.0L Turbo (CAEB) Page 96
^ Verify wiring from UHV to Radio in CAN vehicles.
^ If sound cannot be corrected using above methods/explanations, test and/or replace the UHV control unit.
^ Calls are too quiet
For the other person on the line:
^ Have other person increase speaker volume.
^ Test and/or replace microphone.
^ For 3G & 3G+ vehicles: adjust microphone sensitivity.
Tip: Adjusting the microphone sensitivity on CAN vehicles is not advised, as this can impair other vehicle features, such as Voice
Recognition and Audio Pilot.
For the driver:
^ Increase volume in vehicle.
^ Increase volume on mobile phone (if allowed by phone model).
^ Calls are distorted
^ Reduce volume on mobile phone (if allowed by phone model).
^ Reduce speaker volume.
^ Delete Bluetooth connection on phone and vehicle and re-pair.
^ Reset microphone sensitivity.
^ Verify position of air vents and intensity of blower is not causing microphone interference.
Warranty
This TSB is informational only and not applicable to any Audi warranty.
Additional Information
The following Technical Service Bulletin(s) will provide additional information:
^ TSB 2026851, 91 Belt Microphone Overview
^ TSB 2026895, 91 Microphone Testing Tips
^ TSB 2027718, 91 Bluetooth Phone, call quality poor at other end
All parts and service references provided in this TSB are subject to change and/or removal. Always check with your Parts Department and service
manuals for the latest information.
