Little Known Inhibitor Switch

[KingSasanka]

This I came across in another forum and thought of sharing, in case if it will help another.

This is some technical info about cars with auto transmission gears . The story is directly related to something happened to me during last few days. Non of the four garages visited by me diagnosed the troubles of my car and I almost lost few laks of money due to wrongly diagnosing and actions done by mechanics. That is why I give this information to others. One of the garages is said to be operated by a BSc qualified Engineer. (not Mr Alawaththa)

The entire episode is related to a gadget called 'Inhibitor switch' and I found no one in those repair places knew correctly about it.
I write this because the know-how may help someone someday.

This is a long story.
If you are not interested in 'gadgematics' do not read it.

In auto geared (automatic transmission) cars you can see the gear position in the dash board. When you change the gear lever to P, N, D , R or 1/2 positions it is indicated by lighting the correspondent bulb in the dash board.

Power supply to the starting motor is also connected through the gear lever . Power to the starting motor is only connected when you place the lever in P or N positions. Hence in other positions you cannot start the car.

My problem started with erroneous indications in the dash board. When I changed to D to run the vehicle it shows N although the car runs at D. When the troubles continued I couldn't start the car at P but sometimes it get connected at R or even D.

At the same time when I change the gears the engine shake like doing it half clutch in manual cars.
When I changed from N to D to start running it made 'dug' sound with big shake in the engine and it jump forward with unusual high power.

At this stage I consulted garage people, two places.


One fellow had a test run and diagnosed 'gear cable malfunctioning' or kebal eka edila. So you have to replace the cable to get the correct indication in the dash board.

For the shaking of the engine , he suspected broken engine mounts .

I went to a reliable cable repair place near Subadrarama temple closer to Gram Sabha junction, Nugegoda . They correctly said no error in the cable and didn't charge me a cent and asked me to check the 'gear changing switch'. I did not know where is this switch initially. Later I found that is called the Inhibitor Switch and located externally at the top of the gearbox .

I went to another garage I know. They inspected and gave reasons for the shaking of the engine when changing from N to D.

Diagnosed: Engine mount failure. Some mounts broken or loosened. Replacement cost 6500 + 7500 x 2 = approx 30,000.00 He also suggested changing of the gear cable.
He almost started the job but fortunately, I had an important work and took the car away.

At this stage I could start the car at D or R positions and not P or N. Apart from the big shake at changing N to D or from N to R, I had no trouble when running. I was instructed by the both places if I can start at D and do the running there will be no problem at all, irrespective of what indicated in the dashboard. Sir, that is just to show you the lever position and nothing else, they said.


Within one week another major trouble started. I felt the gearbox is working only at 1 and 2 gears. Normally it should change 1 to 2 at pickup and then to 3 to top levels with the increasing speed, automatically.

Now it changes only once, from lowest to the next . I could not run beyond 35kmph and RPM was much higher than usual.

Again I took the car to the garages . Now the diagnosis was gearbox failure.

As per the experts, all the troubles I had before were signs of this final outcome. Some wheels or parts of the automatic gearbox has damaged and you can't run the car with it. Only Low gear wheels are not broken yet.

Repairing is not advised and what they do normally is fixing a new gearbox. Cost of a used imported gearbox is around 135-150,000.00

No other option now. I have to find two lakhs.

The total job:

Engine mounts : 30,000.00
Gearbox 150,000.00
Inhibitor switch 6000.00
labour cost 25,000.00 approx.

Total 211,000.00

I was not satisfied at all about these garage people in the whole drama. I asked them the functioning of the Inhibitor switch in deep buy they couldn't give me satisfactory answers.

As per them the switch is to track your lever position and indicate it in the dash board and cut the ignition power when you are not at Parked or at Neutral . Nothing else.

I felt suspicious. All started with wrong indication of gear positions at the dashboard . That means the inhibitor switch is broken.

After that the engine and the gearbox started malfunctioning.

Hence, without letting others to remove the broken gearbox I decided to check the inhibitor switch my self.

I removed the battery and its underneath panel to open inhibitor switch area. Normally it is placed under battery at the top of gearbox. (see image)

There was a lever to connect it to the gear cable. The cable is connected to the hand stick inside the car. Inhibitor switch rotates when you change the gears and connect particular wires to send current to dashboard and other places.

I removed and dismantled the switch and found the plastic 'hand' inside was broken.
Hence bought a new one paying 5,500/- with 15% discount.

I connected the new one to the wires and then fixed it to the gearbox .

The correct positioning of gearbox and the switch can be achieved using indicator holes. They are aligned at N position. Then you have to place the gear lever (inside the car) at N position and connect the cable to the lever at top of the switch . In this way you place N inside the gearbox, N at the switch and N at the gear lever fixed to each other.

Connecting current wires to the switch was the most difficult job. It has 9 connectors.

After fixing everything I started the car.

Changed to D. Nothing happened. For a second I thought even first gear is not functioning.
Within second car started to move. I accelerated and had a run .
Amazingly everything became normal . Gear changing is as good as or even better than a new car, done at correct speeds very smoothly . No shakes. No wrong indicator lights. RPM much lover .
No mount problems. Gearbox is perfect.

All the trouble was due to disconnected Inhibitor switch.
Not only to the dashboard, it connects power to reverse light and connects some lines to the car computer.
Actually gear controlling computer 'sees' the gear position using the signal from Inhibitor switch. Without the correct signal the controller cannot guide the gearbox to change the gears smoothly.
That makes it behave badly.

If anybody get this type of problems better to check and replace this switch before going for big work or replacements.

Later I realized there is a designers laziness involved here.
Instead of getting feed back from the gearbox to 'show' the gear position to the controller, the designers has done it in a very bad way.

They fixed a switch in between the the hand gear lever and gearbox and monitor the gear cable to determine what inside the gearbox. If the gear cable elongated or some connectors in the switch weathered or broken its signals become not tallying with actual position. As the controller is blind to see the actual gear box and they made it to 'think' the signal from the switch is from the gearbox it guides the gearbox wrong way.

My total cost was 5,500/- +travelling.
By doing it myself I saved approx 200,000.00.

http://investorsentiment.forumotion.net/t4788-technical-stuff-not-stocks-inhibitor-switch#35939

[Kavvz]

Nice write up, and thanks for sharing

[Crosswind]

See... if the guy had come to autolanka first, he wouldnt have had all this hassle :-)

[Davy]

This is commonly referred to as the "Neutral Safety Switch" and is the first point to check when your vehicle does not seem to be responding according to the gear selector. I believe the mechanical switches tend to give more trouble as opposed to other types of Neutral Safety Switches (electronic ones for example).

Anyway, glad you managed to fix it yourself without blindly replacing the entire gearbox. Good work!

[VVTi]

DIY, FTW.!!!!

Great work!

I had a similar situation with the Forester. Car refuses to start or would not engage properly, like yours. Finally traced the problem to a loose/worn connector from the Inhibitor to the gearbox control unit.

Edited April 3, 2015 by VVTi

[TechHater]

thanks for sharing the info. i have a kia sportage 2013, with 30,000km on the clock. one morning when im trying to take out the car from my awkwardly placed garage which needs lot of twists and turns with multiple gear changes, i felt the vehicle is sluggish on D. when i looked at the dash, the gear position was not displaying, the gear position by the side of the lever was not lit too. i stopped the engine and restarted. every thing was fine.

same day at the work place, it happened again. this time the gearchange made a "dug" sound with slight rattle. same remedy and everything was fine. infact, about 3 weeks are gone and it never happened again.

but i called kia and the advisor told me it has a simple solution and come by for a checkup which i couldnt turn up still

but i went through the internet to find out similar symptoms attributed to " transmission range switch" which gives the correct information to the computer about the correct gear position.

i expect the seniors to put some light on this matter. is it the same thing here also?

[Davy]

thanks for sharing the info. i have a kia sportage 2013, with 30,000km on the clock. one morning when im trying to take out the car from my awkwardly placed garage which needs lot of twists and turns with multiple gear changes, i felt the vehicle is sluggish on D. when i looked at the dash, the gear position was not displaying, the gear position by the side of the lever was not lit too. i stopped the engine and restarted. every thing was fine.

same day at the work place, it happened again. this time the gearchange made a "dug" sound with slight rattle. same remedy and everything was fine. infact, about 3 weeks are gone and it never happened again.

but i called kia and the advisor told me it has a simple solution and come by for a checkup which i couldnt turn up still

but i went through the internet to find out similar symptoms attributed to " transmission range switch" which gives the correct information to the computer about the correct gear position.

i expect the seniors to put some light on this matter. is it the same thing here also?

Not an expert when it comes to automatic transmission, but your issue also could be due to a faulty Neutral Safety Switch. To ensure, you can get the switch tested. It's pretty easy to test the switch (especially if it's a mechanical one).

"Transmission Range Switch" refers to the Neutral Safety Switch/Inhibitor Switch. It's the same thing.

[KingSasanka]

Thank guys and it was enlightening.

[maheshw]

Super work excellnt man...

[terrabytetango]

It's been a while since I've had a good read on the AL forums. Well done indeed, now I know what to look for when this eventually happens to the Vios.

[devonpmb]

Good explanation. My Mazda 3 also having same problem some times. Thanks

[JanithC]

On 4/3/2015 at 12:58 AM, KingSasanka said:

This I came across in another forum and thought of sharing, in case if it will help another.

This is some technical info about cars with auto transmission gears . The story is directly related to something happened to me during last few days. Non of the four garages visited by me diagnosed the troubles of my car and I almost lost few laks of money due to wrongly diagnosing and actions done by mechanics. That is why I give this information to others. One of the garages is said to be operated by a BSc qualified Engineer. (not Mr Alawaththa)

The entire episode is related to a gadget called 'Inhibitor switch' and I found no one in those repair places knew correctly about it.
I write this because the know-how may help someone someday.

This is a long story.
If you are not interested in 'gadgematics' do not read it.

In auto geared (automatic transmission) cars you can see the gear position in the dash board. When you change the gear lever to P, N, D , R or 1/2 positions it is indicated by lighting the correspondent bulb in the dash board.

Power supply to the starting motor is also connected through the gear lever . Power to the starting motor is only connected when you place the lever in P or N positions. Hence in other positions you cannot start the car.

My problem started with erroneous indications in the dash board. When I changed to D to run the vehicle it shows N although the car runs at D. When the troubles continued I couldn't start the car at P but sometimes it get connected at R or even D.

At the same time when I change the gears the engine shake like doing it half clutch in manual cars.
When I changed from N to D to start running it made 'dug' sound with big shake in the engine and it jump forward with unusual high power.

At this stage I consulted garage people, two places.


One fellow had a test run and diagnosed 'gear cable malfunctioning' or kebal eka edila. So you have to replace the cable to get the correct indication in the dash board.

For the shaking of the engine , he suspected broken engine mounts .

I went to a reliable cable repair place near Subadrarama temple closer to Gram Sabha junction, Nugegoda . They correctly said no error in the cable and didn't charge me a cent and asked me to check the 'gear changing switch'. I did not know where is this switch initially. Later I found that is called the Inhibitor Switch and located externally at the top of the gearbox .

I went to another garage I know. They inspected and gave reasons for the shaking of the engine when changing from N to D.

Diagnosed: Engine mount failure. Some mounts broken or loosened. Replacement cost 6500 + 7500 x 2 = approx 30,000.00 He also suggested changing of the gear cable.
He almost started the job but fortunately, I had an important work and took the car away.

At this stage I could start the car at D or R positions and not P or N. Apart from the big shake at changing N to D or from N to R, I had no trouble when running. I was instructed by the both places if I can start at D and do the running there will be no problem at all, irrespective of what indicated in the dashboard. Sir, that is just to show you the lever position and nothing else, they said.


Within one week another major trouble started. I felt the gearbox is working only at 1 and 2 gears. Normally it should change 1 to 2 at pickup and then to 3 to top levels with the increasing speed, automatically.

Now it changes only once, from lowest to the next . I could not run beyond 35kmph and RPM was much higher than usual.

Again I took the car to the garages . Now the diagnosis was gearbox failure.

As per the experts, all the troubles I had before were signs of this final outcome. Some wheels or parts of the automatic gearbox has damaged and you can't run the car with it. Only Low gear wheels are not broken yet.

Repairing is not advised and what they do normally is fixing a new gearbox. Cost of a used imported gearbox is around 135-150,000.00

No other option now. I have to find two lakhs.

The total job:

Engine mounts : 30,000.00
Gearbox 150,000.00
Inhibitor switch 6000.00
labour cost 25,000.00 approx.

Total 211,000.00

I was not satisfied at all about these garage people in the whole drama. I asked them the functioning of the Inhibitor switch in deep buy they couldn't give me satisfactory answers.

As per them the switch is to track your lever position and indicate it in the dash board and cut the ignition power when you are not at Parked or at Neutral . Nothing else.

I felt suspicious. All started with wrong indication of gear positions at the dashboard . That means the inhibitor switch is broken.

After that the engine and the gearbox started malfunctioning.

Hence, without letting others to remove the broken gearbox I decided to check the inhibitor switch my self.

I removed the battery and its underneath panel to open inhibitor switch area. Normally it is placed under battery at the top of gearbox. (see image)

There was a lever to connect it to the gear cable. The cable is connected to the hand stick inside the car. Inhibitor switch rotates when you change the gears and connect particular wires to send current to dashboard and other places.

I removed and dismantled the switch and found the plastic 'hand' inside was broken.
Hence bought a new one paying 5,500/- with 15% discount.

I connected the new one to the wires and then fixed it to the gearbox .

The correct positioning of gearbox and the switch can be achieved using indicator holes. They are aligned at N position. Then you have to place the gear lever (inside the car) at N position and connect the cable to the lever at top of the switch . In this way you place N inside the gearbox, N at the switch and N at the gear lever fixed to each other.

Connecting current wires to the switch was the most difficult job. It has 9 connectors.

After fixing everything I started the car.

Changed to D. Nothing happened. For a second I thought even first gear is not functioning.
Within second car started to move. I accelerated and had a run .
Amazingly everything became normal . Gear changing is as good as or even better than a new car, done at correct speeds very smoothly . No shakes. No wrong indicator lights. RPM much lover .
No mount problems. Gearbox is perfect.

All the trouble was due to disconnected Inhibitor switch.
Not only to the dashboard, it connects power to reverse light and connects some lines to the car computer.
Actually gear controlling computer 'sees' the gear position using the signal from Inhibitor switch. Without the correct signal the controller cannot guide the gearbox to change the gears smoothly.
That makes it behave badly.

If anybody get this type of problems better to check and replace this switch before going for big work or replacements.

Later I realized there is a designers laziness involved here.
Instead of getting feed back from the gearbox to 'show' the gear position to the controller, the designers has done it in a very bad way.

They fixed a switch in between the the hand gear lever and gearbox and monitor the gear cable to determine what inside the gearbox. If the gear cable elongated or some connectors in the switch weathered or broken its signals become not tallying with actual position. As the controller is blind to see the actual gear box and they made it to 'think' the signal from the switch is from the gearbox it guides the gearbox wrong way.

My total cost was 5,500/- +travelling.
By doing it myself I saved approx 200,000.00.

http://investorsentiment.forumotion.net/t4788-technical-stuff-not-stocks-inhibitor-switch#35939

After 4 years time, this help me a lot. Thank you Kingsasanka. I found the error now. Many Garages working without proper knowledge. OBD code is P0706