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KIA TRS/Inhibitor Switch Replacement (Fix for OBD Code P0705 or missing gear display)

59K views 16 replies 11 participants last post by  Bcsmitty  
#1 · (Edited)
I recently had a CEL on my 2011 Kia Optima and also weird behavior with the A/T (gear indicator on dash was blank and sometimes the A/T wouldn’t automatically shift all the way down to 1 at stops sometimes). I bought my own code reader (only cost ~$30 on Amazon) and the code I got was P0705 which indicated a problem with the Transmission Range Sensor (TRS) which is also sometimes referred to as the Automatic Transmission Inhibitor Switch or the Neutral Safety Switch. This appears to be a pretty common problem on both Kia and Hyundai. Fortunately, the fix is really simple – all you have to do is swap out the TRS. On all these vehicles (Kia Optima, Kia Sorrento, Hyundai Elantra) the TRS is located in the front driver-side quadrant of the engine bay (the bottom-right if you are looking under the hood). To replace it, you simply need to remove the air intake, battery and battery holder and the TRS is right there just underneath the battery holder. If you know what you are doing and fast, this can be done in as little as 20 minutes although I really took my time and triple-checked everything.

The TRS is basically just a device which senses what position/gear the car is in and sends that information back to the computer. This allows the car to display the current gear on the dashboard and it may also prevent the car from starting if the computer believes that the car is not in Park/Neutral. I bought mine from kiapartsnow.com and it only cost ~$50 shipped. Aside from that part, the only tools you need are a ratcheting socket wrench (or driver) with 10mm, 12mm and 14mm sockets and also a small flat-head screwdriver (just to pop off the wire connecting the TRS).

For my vehicle, the current version of the part is 4270026700. The current version has metal housing and looks a lot more robust than the older version. The holes and connections all go in the same way. (Note that the OLD version of this is 4270026000 or -45956B. Do not use the older version as I believe those are more prone to have this problem again in the future.)

*** SAFETY WARNING ***

Absolutely make sure that you set the parking break AND chock the tires before starting. The reason why is that the TRS connects to the AT gear shift and it is easy to switch gears on accident while you are working on the vehicle and knock it out of park. In fact, that happened to me while I was working on mine.

*** STEPS ***

Image


Image


1) Remove the air intake. Unscrew 2x 10mm bolts. Then lift the unit slightly up and pull it straight towards you. It will slide right out.

2) Disconnect the battery. Terminal connections are 2x 10mm. Remove negative first. Make sure you cover the terminals so that you don’t accidentally touch or short the battery.

3) Remove the battery. There is a retainer at the front of the base. 1x 12mm bolt.

Image


4) Remove the battery tray. 4x 12mm in the tray and 2x 10mm at the top. After removing the bolts, I just rested the battery tray out of the way towards the front.

Image


Image


5) Remove the old TRS. 1x 14mm nut in the center. 2x 10mm bolts on the sides. Do NOT touch the nut on the right side of the arm – only the 1 nut and 2 bolts on the TRS itself. Once you remove those, lift off the arm and then lift off the TRS. Then disconnect the wire from the TRS – you will probably need a flat-head screwdriver to release the wire.

Image


6) Install new TRS. If it doesn’t slide right back on, you might need to either wiggle it on or turn the hole in the center to line up with the bolt. Also, if the metal arm does not slide right back on the bolt, you may have bumped the center bolt (which controls the AT gear). Just use a vice grip or wrench to turn the gear back to the correct position. As long as the gear selection bolt is in the correct position, the arm should slide right back on. Once the TRS and arm are on, screw back in the 2 bolts and 1 nut. You might need to screw on the 2 bolts before attaching the arm.

7) Re-install battery tray. 6 bolts(4x 12m + 2x 10mm).

8) Re-install battery. 1 retaining clip and bolt. Then re-connect both wires – I attach positive first.

9) Re-install intake. Slide it back on and then 2 bolts.

10) When everything is done, take a test drive around the block to make sure everything is working. All gears should work and show up on the dashboard.

11) Reset the OBD “Permanent DTC”. If you don’t do this, the trouble code might stay in the computer (even if the CEL is gone) and you will NOT pass SMOG/Inspection. To do this you need to do the “Universal Trip Drive Pattern”: Start Car. Idle for 30+ seconds. Drive for 5+ minutes at normal speed (total drive time should be 10+ minutes). Idle car for 30+ seconds. Turn off. To verify that the “Permanent DTC” is removed, you will need to use a code reader.


*** RESOURCES and REFERENCES ***

OBD Code P0705:
https://www.obd-codes.com/p0705

This is the part that you need:
KIA TRS/AT Inhibitor 4270026700: https://www.kiapartsnow.com/genuine/kia-switch-inhibitor~4270026700.html

Optional if you want to replace these:
NUT: 1311FA https://www.kiapartsnow.com/genuine/kia-nut~1311110007k.html
WASHER: 1360CF https://www.kiapartsnow.com/genuine/kia-washer-spring~1360210006k.html
2 BOLTS: 1140EP https://www.kiapartsnow.com/genuine/kia-bolt~1140306226k.html

TSB: https://f01.justanswer.com/mbrauto/0db6607f-35cd-4cda-ad06-8296853b1864_2015_Kia_Sorento.pdf

Video showing replacement on Hyundai Elantra:

Pictures showing replacement on Kia Sorrento: https://www.kia-forums.com/2011-2013-xm-sorento-forum/208177-2011-kia-sorento-p0705.html

Another related thread: https://www.optimaforums.com/forum/170-service-center/166979-trs-warranty.html

How to remove Permanent DTC from computer: https://www.autoserviceworld.com/carsmagazine/taking-a-first-look-at-permanent-dtcs/

Image Gallery: https://imgur.com/gallery/6DEAaqd
 
#2 ·
Excellent excellent DIY! Well done!
 
#4 ·
NOTE: Additional symptoms which may require the replacement of the TRS / Neutral Safety Switch include intermittent No Start condition. When this happens, the starter just clicks like a bad battery but the battery will test fine and the car may start fine on a subsequent attempt or it may be necessary to re-seat the car in park (move the shifter). The reason why this happens is because part of the function of the TRS is to ensure that the car is in the proper gear before starting up for safety.

Also, there is an additional DIY here for more information:
 
#5 ·
Hi, we have 2013 Kia Optima SXL and we replaced our Neutral Safety Switch about 4 months ago. Unfortunately when removing the old from the electrical plug clip one of the little plastic pieces broke that helps secure the plug to the part broke. We were still able to install it since we purchased the one and only available switch in our area that day and it started fine and has been running fine. By the way, ours would not start at all until we replaced the switch. Anyway, a week ago I could not start my car and noticed if I pressed the brake and put in any gear and then back to park it would start. This is obviously very dangerous. So, we checked and while it still appears completely seated into the plug possibly it is not a secure fit. We have done and exhausted research and cannot determine which wiring plug to order to replace. Does anyone know the correct wiring plug (harness) to purchase? Many thanks for any help. I don't want to be stranded somewhere! This should be a factory recall!
 
#8 ·
This will be our 3rd replacement. I am baffled as to why this TRS or Neutral Safety Switch would continue to go bad. The first one I replaced with a switch from Autozone. It went bad in 4 months! The 2nd one I bought directly for Kia thinking I needed an OEM possibly. Now, 10 months later, bad again! I have a 2013 Kia Optima SXL. Of course my local Kia dealer does not stock it so they have to reorder one. Takes two days but will be under the 12 month part warranty. No car for two stinken days!! Why did this part go bad? I have to be super careful when reinstalling because my husband broke one of the plastic pins on the wiring harness but it seated tightly. So frustrating!!!! Kia wants $150 to try and diagnose the reason but I think they will not be able to tell me why. This should be a recall all day long!
 
#9 ·
Holy crap! Digging up an old post. I am ready to trade in my Optima due to something along these lines! I ripped out my remote start, thinking that was the problem. Battery would act dead or read dead.. Went through three batteries thinking it was the battery. I would get the Immobilizer logo constantly and car wouldn't start. Or it would "act" like it is starting but not actually turn over then the dash/radio would act like it started(but not start). I'm wonder if this is actually my issue. It can be two weeks with ZERO issues and then BAM car is dead/won't start! Is there anyway to actually test the TRS? I'm not throwing any codes.
 
#10 ·
I also had to replace mine but did so with the improved OEM version (this was in 2019). No issues since then. I posted about it at the time on these forums.
 
#11 · (Edited)
I have a 2011 Sorento and found this wonderful post! Old I know but nicely done. Only one thing I didn't realize I was reading about and Optima and not a Sorento. My Bad. I purchased the part # given as new and improved and car would not start no mater what. Looking closer the original switch had 5 pins in the plug and switch. The new #4270026700, stated above, has more. Like 8. . Trying to return a $70 part, hopefully, and buy what Kia says is the most recent superseded part, #42700-3B010. Hope this save someone some grief.
 
#12 ·
I also have a 2011 Sorento and found this wonderful post! Old I know but nicely done. Only one thing. I purchased the part # given as new and improved and car would not start no mater what. Looking closer the original switch had 5 pins in the plug and switch. The new #4270026700, stated above, has more. Like 8. I'm not sure how this could have worked for the original poster even though it plugs in fine. Trying to return a $70 part, hopefully, and buy what Kia says is the most recent superseded part, #42700-3B010. Hope this save someone some grief.
Hey sorry, 4270026700 was the latest part number for the Optima specifically. Sounds like the Sorento uses a different one.

Check here and use the part checker function on the product page. Fortunately, most of them are $35-50.
 
#13 ·
Does anyone know if this would cause the battery to randomly drain as well? I'm not throwing any codes but I am having issues getting my optima to start randomly. The key immobilizer dash light comes up blinking. I've replaced the car battery, I've replaced the battery in the remote. The car will be fine for a week and then randomly just not start. Sometimes disconnecting and reconnecting the battery lets me start it.
 
#14 ·
Did the battery actually drain (ie you tested it and it had low voltage)? The TRS problem won't drain the battery itself. However - it can have no start as a symptom. That was the first obvious symptom that I had. My car would just randomly not start (felt like a dead battery) but then I would try a few more times and it would work. My battery was fine when tested though.
 
#16 ·
I recently had a CEL on my 2011 Kia Optima and also weird behavior with the A/T (gear indicator on dash was blank and sometimes the A/T wouldn’t automatically shift all the way down to 1 at stops sometimes). I bought my own code reader (only cost ~$30 on Amazon) and the code I got was P0705 which indicated a problem with the Transmission Range Sensor (TRS) which is also sometimes referred to as the Automatic Transmission Inhibitor Switch or the Neutral Safety Switch. This appears to be a pretty common problem on both Kia and Hyundai. Fortunately, the fix is really simple – all you have to do is swap out the TRS. On all these vehicles (Kia Optima, Kia Sorrento, Hyundai Elantra) the TRS is located in the front driver-side quadrant of the engine bay (the bottom-right if you are looking under the hood). To replace it, you simply need to remove the air intake, battery and battery holder and the TRS is right there just underneath the battery holder. If you know what you are doing and fast, this can be done in as little as 20 minutes although I really took my time and triple-checked everything.

The TRS is basically just a device which senses what position/gear the car is in and sends that information back to the computer. This allows the car to display the current gear on the dashboard and it may also prevent the car from starting if the computer believes that the car is not in Park/Neutral. I bought mine from kiapartsnow.com and it only cost ~$50 shipped. Aside from that part, the only tools you need are a ratcheting socket wrench (or driver) with 10mm, 12mm and 14mm sockets and also a small flat-head screwdriver (just to pop off the wire connecting the TRS).

For my vehicle, the current version of the part is 4270026700. The current version has metal housing and looks a lot more robust than the older version. The holes and connections all go in the same way. (Note that the OLD version of this is 4270026000 or -45956B. Do not use the older version as I believe those are more prone to have this problem again in the future.)

* SAFETY WARNING *

Absolutely make sure that you set the parking break AND chock the tires before starting. The reason why is that the TRS connects to the AT gear shift and it is easy to switch gears on accident while you are working on the vehicle and knock it out of park. In fact, that happened to me while I was working on mine.

* STEPS *

Image


Image


1) Remove the air intake. Unscrew 2x 10mm bolts. Then lift the unit slightly up and pull it straight towards you. It will slide right out.

2) Disconnect the battery. Terminal connections are 2x 10mm. Remove negative first. Make sure you cover the terminals so that you don’t accidentally touch or short the battery.

3) Remove the battery. There is a retainer at the front of the base. 1x 12mm bolt.

Image


4) Remove the battery tray. 4x 12mm in the tray and 2x 10mm at the top. After removing the bolts, I just rested the battery tray out of the way towards the front.

Image


Image


5) Remove the old TRS. 1x 14mm nut in the center. 2x 10mm bolts on the sides. Do NOT touch the nut on the right side of the arm – only the 1 nut and 2 bolts on the TRS itself. Once you remove those, lift off the arm and then lift off the TRS. Then disconnect the wire from the TRS – you will probably need a flat-head screwdriver to release the wire.

Image


6) Install new TRS. If it doesn’t slide right back on, you might need to either wiggle it on or turn the hole in the center to line up with the bolt. Also, if the metal arm does not slide right back on the bolt, you may have bumped the center bolt (which controls the AT gear). Just use a vice grip or wrench to turn the gear back to the correct position. As long as the gear selection bolt is in the correct position, the arm should slide right back on. Once the TRS and arm are on, screw back in the 2 bolts and 1 nut. You might need to screw on the 2 bolts before attaching the arm.

7) Re-install battery tray. 6 bolts(4x 12m + 2x 10mm).

8) Re-install battery. 1 retaining clip and bolt. Then re-connect both wires – I attach positive first.

9) Re-install intake. Slide it back on and then 2 bolts.

10) When everything is done, take a test drive around the block to make sure everything is working. All gears should work and show up on the dashboard.

11) Reset the OBD “Permanent DTC”. If you don’t do this, the trouble code might stay in the computer (even if the CEL is gone) and you will NOT pass SMOG/Inspection. To do this you need to do the “Universal Trip Drive Pattern”: Start Car. Idle for 30+ seconds. Drive for 5+ minutes at normal speed (total drive time should be 10+ minutes). Idle car for 30+ seconds. Turn off. To verify that the “Permanent DTC” is removed, you will need to use a code reader.


* RESOURCES and REFERENCES *

OBD Code P0705:
P0705 Transmission Range Sensor Circuit Malfunction (PRNDL input)

This is the part that you need:
KIA TRS/AT Inhibitor 4270026700: 4270026700 Genuine Kia Inhibitor Neutral Safety Switch

Optional if you want to replace these:
NUT: 1311FA 1311110007K Genuine Kia Nut
WASHER: 1360CF 1360210006K Genuine Kia Washer-Spring
2 BOLTS: 1140EP 1140306226K Genuine Kia Bolt

TSB: https://f01.justanswer.com/mbrauto/0db6607f-35cd-4cda-ad06-8296853b1864_2015_Kia_Sorento.pdf

Video showing replacement on Hyundai Elantra:

Pictures showing replacement on Kia Sorrento: 2011 Kia Sorento p0705

Another related thread: TRS warranty

How to remove Permanent DTC from computer: Taking A First Look At Permanent DTCs - Auto Service World

Image Gallery:
One of the best responses I've seen on this website! Kudos!!!
 
#17 ·
So o was able to do everything and then went to put the metal arm on, went on but doesn’t line up with bolt hole on piece. The arm that the metal arm is attached to it extended so I can’t really adjust it so it works. What should I do?