How does the auto inhibit switch work?
 

I have an Auto that starts in Drive.

It was thought that the car may have had a manual ecu fitted at some time, but it has been T4’d by Jules who confirmed this is not the case. He has confirmed a correct auto ecu all correctly matched to the car, and suspects the auto inhibit switch may be faulty.

These are quite expensive so i wondered at first if anyone knows how they work, because the display in the message centre correctly shows the status of the gear lever, and knows that it is in Drive, yet still allows the engine to start.

So does the switch have 2 switch outputs in it? Does anyone know how to test one with a multimeter perhaps?

I believe this is the switch in question..

http://i.imgur.com/vWQpmqu.jpg

You should be able to see on T4 what gear is selected, back to Jules for a quick plug in I reckon!

It is going back to Jules soon to have the work finished, and i was suggested to obtain a new inhibit switch, but they are around £100 on ebay, and for that money i was hoping to test my switch somehow first to confirm it is faulty.

At the moment when i move the lever through each of the positions, the display on the instrument panel correctly changes to match, and yet the car will still start in all gears.

That is why i thought maybe the switch has more than one output. Maybe it can be cleaned or repaired?

I'd PM some of the traders here, I suspect you'll get a switch for considerably less than a hundred quid.

You may want to do a bit more investigation before forking out for another switch. My ZT 180 Auto suffers the same problem and I thought it must be the switch. Bought another one from a breaker for £70 (!) and had it fitted but it made no difference. OK, the second one might have been faulty, but seemed an unlikely coincidence. My investigations at the time seemed to show that they weren't available new anywhere, so I gave up and just take care about gear position when starting. It is annoying, though, and I'd love someone to be able to isolate exactly where the problem is.

Exactly my thoughts. Cheapest i found is £49. For that money i want to know its going to fix the problem. I would like to know how it works when it is clearly sending out a signal to the instrument panel correctly. Must be another signal that doesnt show somewhere that does the “inhibit” function.

It would be good to get hold of another one to open up and find out how it works. Maybe mine can be cleaned or repaired somehow.

Haynes manual says this fault may be either a faulty inhibitor switch or the selector cable needs adjustment .

Haynes manual also shows how to set the switch adjustment when fitting it

I believe that it is the ews that provides the starter inhibit.
It receives a signal on a pin to indicate the car is in park, and if that signal is present (along with the rest of the immobiliser inhibits) then the car can turn over.
On a manual this pin is not connected, and the ews is programmed not to check the state of this pin. This programming can be done using Toaf - may be worth checking to make sure the ews does not think it is a manual.

I don't have the wiring diagrams to hand to check where the signal to the ews originates though.
Hope this helps
Chris