Transmission Control Unit, how to change it out?

Tiny
MIRIAM BROWN
  • MEMBER
  • 2003 HYUNDAI SANTA FE
  • 2.7L
  • 6 CYL
  • 2WD
  • AUTOMATIC
  • 164,027 MILES
Clunking sound going into reverse, initially. Mechanic test drove and said either tranny or engine bolts. Now, it jerks going into reverse so stopped driving it. My Autel diagnosed Transmission Control Unit problem. Bought a used one from Ebay and can't find a YouTube video to demonstrate how to change it out. Called different shops for an estimate but none called back. All too busy. I live in Lower Queen Anne and need it soon to move. Any suggestions? Thanks.
Tuesday, May 2nd, 2023 AT 8:28 PM

32 Replies

Tiny
KEN L
  • MASTER CERTIFIED MECHANIC
  • 51,710 POSTS
Sure, it looks like the TCM/PCM is by the throttle pedal here is the location in the images below. Please let us know if you need anything else to get the problem fixed. I would check the U joint is the driveshaft, transmission and engine mounts as well.
Images (Click to make bigger)
Thumb
Thumb
Was this
answer
helpful?
Yes
No
+1
Wednesday, May 3rd, 2023 AT 11:43 AM
Tiny
MIRIAM BROWN
  • MEMBER
  • 18 POSTS
Can you recommend a step-by-step instruction video or written explanation telling how to switch out the old with the "new"(used)? Do I need to remove the battery cable first to save the codes? Also, I can't find a mechanic near me (Lower Queen Anne). Can you refer me to one? Lastly, is it safe to drive it to the shop?
Thankfully, Miriam
Was this
answer
helpful?
Yes
No
Thursday, May 4th, 2023 AT 9:56 AM
Tiny
KEN L
  • MASTER CERTIFIED MECHANIC
  • 51,710 POSTS
Yep, sorry about that. Here is a guide to help you change the unit out, also you can get a preprogrammed unit by searching Google or Ebay. I am sorry we don't know of any shops in your area that can help. You can use google maps to find reviews and the locations of the shops and then call them.

Please go over this guide and report back.
Was this
answer
helpful?
Yes
No
Friday, May 5th, 2023 AT 9:42 AM
Tiny
MIRIAM BROWN
  • MEMBER
  • 18 POSTS
Thank you so much for the step-by-step instructions to replace the TCM. As soon as the rain lets up, I give it a try.
God bless you! Miriam
Was this
answer
helpful?
Yes
No
Friday, May 5th, 2023 AT 5:41 PM
Tiny
MIRIAM BROWN
  • MEMBER
  • 18 POSTS
Hi, again. As you know, I am not a mechanic, however, I am determined to fix what I can fix. To wit, I followed your instructions and discovered that 1) There is an insulated cable on top of the unit. Additionally, the bolt that needs to be removed from the right side of the bracket is unreachable. I assume that someone else needs to be removed to get at it. You can only see it on a cell phone. There is a yellow collapsible tube running to the back seat. Probably not necessary to remove, right?
I am so close, unhooked the battery cable, wore the wrist strap, bought the silicone grease, got the wiring harnesses off and now what? Do I need to remove something else in order to get at the bolt securing the TCM? I really appreciate your help!
70 yr. Old grandma Miriam. P.S. It sucks to be old and poor.
Was this
answer
helpful?
Yes
No
Friday, May 12th, 2023 AT 6:55 PM
Tiny
KEN L
  • MASTER CERTIFIED MECHANIC
  • 51,710 POSTS
I am sorry, please upload images of what you are seeing so I can help walk you through it.
Was this
answer
helpful?
Yes
No
Saturday, May 13th, 2023 AT 10:21 AM
Tiny
MIRIAM BROWN
  • MEMBER
  • 18 POSTS
Here are photos of the transmission unit and bracket with the bolt on the right bracket. It looks like the unit has to slide up vertically but there is an insulated cable above the unit and it is secured tight in the bracket.
Images (Click to make bigger)
Thumb
Thumb
Thumb
Was this
answer
helpful?
Yes
No
Sunday, May 14th, 2023 AT 8:19 PM
Tiny
KEN L
  • MASTER CERTIFIED MECHANIC
  • 51,710 POSTS
Yep, it looks like it is close good job so far, it looks like there are 10mm bolts holding the bracket down, but can you slide the unit toward the gas pedal, there might be hold down clips? Let me know.
Was this
answer
helpful?
Yes
No
Monday, May 15th, 2023 AT 10:04 AM
Tiny
MIRIAM BROWN
  • MEMBER
  • 18 POSTS
Hi again. Got the two bolts on the right side but can only lift the unit off the bracket on the right side. Can't see any bolts on the left side. The black insulated hose is tight on that side. Also, tried to pull it straight out towards the accelerator pedal but it has to be lifted off the right back remaining bolt. Only the nut came off. Could you send me a pic of any clips that may be holding it in on the left side? I really appreciate your assistance.
Was this
answer
helpful?
Yes
No
Saturday, May 20th, 2023 AT 7:30 PM
Tiny
KEN L
  • MASTER CERTIFIED MECHANIC
  • 51,710 POSTS
Hi Miriam,

The images above all they show, can you access the TCM from the other side of the dash to see what's going on? Please upload images of what you see so I can help.
Was this
answer
helpful?
Yes
No
Sunday, May 21st, 2023 AT 11:36 AM
Tiny
MIRIAM BROWN
  • MEMBER
  • 18 POSTS
Sorry, don't know if these will help. The unit seems to be dislodged, but couldn't lift the left side up enough to move it out, towards the accelerator pedal. I felt around the left side, and it felt like there is a bolt in the front. Could that be holding the unit to the left. Bracket?
Images (Click to make bigger)
Thumb
Thumb
Thumb
Thumb
Thumb
Was this
answer
helpful?
Yes
No
Sunday, May 21st, 2023 AT 2:28 PM
Tiny
KEN L
  • MASTER CERTIFIED MECHANIC
  • 51,710 POSTS
Yep, that looks like the PCM needs to come out first which is the box on the top of the TCM. Can you see how to remove it? There should be a clip or hold down bolt.
Was this
answer
helpful?
Yes
No
-1
Monday, May 22nd, 2023 AT 11:10 AM
Tiny
MIRIAM BROWN
  • MEMBER
  • 18 POSTS
I finally got the nut off the front left bracket of the TCU. Couldn't get it out of the driver's side so removed the panel off the passenger side. Then I pushed the unit towards the pass. Side and was able to jiggle it out from that side. Hurrah! Now, how do I get it off the brackets?
Was this
answer
helpful?
Yes
No
Wednesday, May 24th, 2023 AT 7:38 PM
Tiny
KEN L
  • MASTER CERTIFIED MECHANIC
  • 51,710 POSTS
Good job! Please upload an image of what you are talking about
Was this
answer
helpful?
Yes
No
Thursday, May 25th, 2023 AT 5:12 PM
Tiny
MIRIAM BROWN
  • MEMBER
  • 18 POSTS
Sent three pics. I can't slide them out, even using a large screwdriver. Do I need to try to find brackets for the replacement unit?
Images (Click to make bigger)
Thumb
Thumb
Thumb
Thumb
Was this
answer
helpful?
Yes
No
Saturday, May 27th, 2023 AT 4:55 PM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 110,114 POSTS
Hi,

I noticed it has been a couple of days since we made contact with you. Have you been able to make any progress?

As far as the brackets, take a thin straight screwdriver and slide it down into where I have an arrow pointing to depress the locking tab I circled. That should release the bracket.

Let me know.

Take care,

Joe

See pic below.
Image (Click to make bigger)
Thumb
Was this
answer
helpful?
Yes
No
+1
Monday, May 29th, 2023 AT 9:09 PM
Tiny
MIRIAM BROWN
  • MEMBER
  • 18 POSTS
Yes, I used a thinner screwdriver, and the bracket flew across the room. Installed the "newer" TCU from the passenger side. Couldn't get the front bolt to line up, so I wiggled the unit and it was immoveable. Forgot to use the silicon on the plugs, but they went in easily. The ck. Engine light wasn't on and no clunking sounds when I took it for a test drive! Should I disconnect the three plugs and put the silicon on or not? Tomorrow, I'll test it again with the Autel diagnostic tester.
Thanks for all your help; I feel ok driving again.
Miriam
Was this
answer
helpful?
Yes
No
Tuesday, May 30th, 2023 AT 7:22 PM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 110,114 POSTS
Hi,

That is good news. I'm glad to hear it is running well again. As far as using dielectric grease on the spark plug boots is concerned, it is a good idea. It keeps moisture out and prevents the boot from being damaged when it is removed.

Regardless, thank you for the update. If anything changes, let us know. Also, feel free to come back anytime in the future.

Take care,

Joe
Was this
answer
helpful?
Yes
No
Wednesday, May 31st, 2023 AT 8:51 PM
Tiny
MIRIAM BROWN
  • MEMBER
  • 18 POSTS
I asked if I needed to grease the three wiring harnesses that I plugged into the TCU, not the the spark plug boots. Wanted to know if it's necessary before putting the trim back on.
Was this
answer
helpful?
Yes
No
Thursday, June 1st, 2023 AT 1:43 PM
Tiny
MIRIAM BROWN
  • MEMBER
  • 18 POSTS
And, do I spread a small amount of the dielectric grease on the male plugs?
Was this
answer
helpful?
Yes
No
Thursday, June 1st, 2023 AT 1:45 PM

Please login or register to post a reply.

Related Transmission Computer TCM Replace/Remove Content

VIEW MORE