Aux audio input fault on Gen II Prius - A Cheap Repair that works (Part 86190-53010)

I have a 2007 Prius T Sprit, which has been developing an annoying fault over a few years. It’s nice that this model came with an aux socket for the stereo into which you can plug iPods, phones etc.. The socket sits in the centre console, alongside a 12v ‘cigarette lighter’ socket.

To listen to whatever is plugged into the socket you press the CD/AUX button on the stereo head unit. If there’s nothing plugged into the socket, the system doesn’t even offer you the option of selecting Aux. It’s just a CD button. Once you stick a jack plug in the socket, the head unit’s CD/Aux button switches between the CD and the Aux input.

The Fault

The car has been gradually ignoring the fact that I had inserted a jack plug into the socket. In the early days a quick jiggle would fix it. Latterly it became harder to make the head unit appreciate that something was plugged in. Then recently it’s actually never worked.

I lifted out the centre console (not hard but there are some tricks, which I won’t go into here), and identified the part number as 86190-53010.



Replacements can be bought on eBay - for about £50! In fact there’s a replacement part that Toyota issued as part of a warranty repair, (Toyota Service Bulletin TSB2810). My Toyota dealer said he couldn’t even get me all three parts, and the two which he could supply totalled more than £100. Seriously?

Thanks

I must thank Robinhood4x4 on the Toyota120 forum, for giving me some ideas. He actually had a 4th gen 4runner, but the part that caused him problems was the same as in my Prius.

The solution (Needs a soldering iron)
First you need to take the unit apart



Just push on the retaining tabs (1) on each side whilst pulling the end part (2) off, as shown.

You should then be able to extract the circuit board, and have three main parts



The circuit board does some fancy switching when there’s a plug in the jack socket. The plug that connects this unit to the stereo head unit has 4 wires; the usual three for the stereo signal, plus one that’s used to signal that there’s a jack plugged in (I’ll call this the ‘jack-signal’ wire).

When the jack socket goes bad, it fails to open the necessary contact, so the wire never receives the signal. In a working unit the resistance presented between the audio ground wire and the jack-signal wire changes:

No jack in the socket: 14.8 kilohm
With a jack in the socket: 2.6 kilohm

I noticed that the two resistors on the board would have a combined resistance of 2.6 kilohm if they were in parallel.

I figured that – without having to try to repair or replace the little jack socket – I could convince the head unit there was always a jack plug in the socket if I connected the two resistors in parallel permanently.
Here's the circuit board as I found it, with the resistor connections highlighted:



Below you can see what I did. It could be neater – but who’s ever going to see it!?



This now works. Your mileage may vary – so beware that this fix may not work for you. However, if the part number on your faulty unit is 86190-53010, it ought to work.