I bought the audio cable to connect the iPhone 4S with the audio system a Ford Fiesta MK7. Unfortunately, the coupling works because with extremely poor quality. There is strong "buzz" in the compound, so that even extremely understanding audiobooks difficult. Annoyed I wanted to then return the same cable. However, the AUX input of the Fiesta is generally in order, because a coupling jack to jack showed no distortion (its just extremely quiet).
For safety, I have it on AUX input of cheap radios and the AUX input of a Ford Focus (BJ: 2010) tested. There, the cable worked, however, no loss of quality.
Conclusion: cable does not work only in the Ford Fiesta MK7. On other devices, the cable is very easy to use.