Difference? TPS/Transmission Input Sensor

Greetings all,

This is my first post on
I am a very proud owner of a '98 Cherokee Classic 2WD with over 200,000 miles. I've been a reader of your forums for some time now, but it has always been for all my pipe dreams like 4 wheel disc break conversions or that monster lift guide. Today though, I'm posting to see if the community can shed some light on my transmission sensor problem.

Well, I've had assorted transmission problems for some time now. I can trace the root of my problems to when i sank my XJ to its cup holders back in 2004. Since then, I've replaced sensors and solenoids on the trany and I've had fairly reliable performance out of the vehicle in between shop visits. I have a new issue that has been a pain in the neck to fix.

***MY ISSUE***:skull2:
-It started out as a minor annoyance where, when i would step on the gas, the vehicle would have some hesitation. It was almost as if it wasn't registering me stepping on the gas at all. The fix was easy enough though, I would pump the gas lightly when it would goof, and all would be well. This inconvenience has, in the past 5 months, become a safety issue. It is a daily occurrence now and can get quite severe in city driving situations.

It is almost like the engine and the transmission are having difficulty working together. It feels like the engine wants to rev, but the transmission wont let it.

***THE TRANSMISSION GUY***
-So i have a transmission guy that I've been going to for a couple of years. He replaced the solenoids on the transmission before and did the work at a fair price, and HE SPEAKS ENGLISH! :roll:

He ran a diagnostic on my transmission and pulled up that it needs an input sensor on the transmission replaced. He says his parts dealer sells them for $300 bucks!!! I go to auto zone and they sell them for like $115. He installs the part and guess what..? I still have the same issue. My transmission still has the same error code. He tells me that I bought the output sensor instead of the input. I go back and try again.

I go to auto zone again and they say that there is no such thing as an input sensor... They direct me to a local transmission shop for more assistance. I go the the local guy and he says the same thing. "no such thing as an input sensor," he even shows me a Chrysler transmission with only one sensor on it.

(Back story -My transmission guy had to leave for the weekend so his dad 'the old man' is running the shop)
I call up my transmission guy and tell the old man that no one has ever heard of an input sensor for that transmission. I guess he gets offended that I'm asking questions at another transmission shop and he tells me that if I want, I can pick up my jeep and take it there. I cool the old man down and say I'm not interested in that option. I ask when his son will be back. He says 3 weeks :bawl:

***THE SEARCH***
One of the last things the old man told me was to go to the dealership and they will have the part. In my mind, if this part is really $300, I'll just buy a couple used ones out of the junk yard and put them in myself if i can.

I go to the dealership, same thing; they tell me that they have nothing in their computer that says input sensor, but they have plenty of solenoids :-\ He gives me a print out... I begin my online research.

Online I find that my transmission is a AW-4 and that later versions of the AW-4 do in fact have an input speed sensor
http://www.naxja.org/forum/showpost.php?p=244762372&postcount=2
My searches for the part number have come up empty handed though.

I ran into this post where someone describes an issues that is very similar to mine. http://autorepair.about.com/library/a/1g/bl070g.htm
They were told that the issue was a TPS or throttle positioning sensor.

***THE QUESTION***
The locations for the TPS is suppose to be on the bell housing and the location of the input speed sensor is described as being on the left front portion of the transmission. Are these in fact the same sensor?!?! Have I been on this wild goose chase for 3 weeks now because I was told the sensor was by a different name?

Please, if anyone can help me figure out what I need to be looking for, I'd appreciate it. :dunno:

Thanks for reading!
-Fishouse

The TPS is on the side of the throttle body. It tells the computer how far open the throttle plate is and how much fuel to deliver.

The sensor it sounds like you are talking about is the crank position sensor. Its mounted in the top driverside of the bellhousing. They are known for crapping out but are a far cry from $300 bucks.

Stop going to IdiotZone for parts or for Tech info. The trained monkeys only know what the computer monitor tells them and there are proven errors in the IdiotZone and the Advance Auto Parts databases.


98-01 AW-4

0.75:1 OD ratio
23 spline output shaft
Electrical connections late model 8 pin wire connector
Two transmission speed sensors (input and output)

The Crankshaft Position Sensor (CPS) is on the Bell Housing and is really not involved with the transmission.

1998+ AW-4 have input and output sensors.

The Throttle Position Sensor (TPS) on the Throttle Body has input to the computers for shifting and shift points. If the TPS is failed you will have shifting issues.

Go here - ************************************* - for a complete AW-4 Service and Diagnostics manual.

I was looking into the possibility of Crankshaft Position Sensor (CPS/CKP) being the culprit, and I have to agree with TIM that the sensor is not associated with the transmission.

CKP syptoms almost always seem to be related to starting or idleing issues. Although, I do have issues from time to time where my vehicle does not idle properly when at an idle for over 10 minutes, I think it may be associated to my other sensor in question.

1998+ AW-4 have input and output sensors.

The Throttle Position Sensor (TPS) on the Throttle Body has input to the computers for shifting and shift points. If the TPS is failed you will have shifting issues.

Click to expand...

Thanks!

I found two sensors that could be it:
page 94

page 111


Can anyone verify which one it probably is? I'm leaning more towards the second one because it looks easier to install on my own

I'm pretty sure that this is the sensor that I made the mistake of buying last time:
http://www.autopartswarehouse.com/d...apwcid=P1135867996W43b3f85c7ab9e&apwidP91ZDma


I think i found it in the PDF, but it looks like it has a slightly different style. The PDF one has a pigtail attached. Both are located at the rear of the transmission.

uhh... upon inspection of my posts, it looks like they are all the output sensor. Where the heck is that darn input sensor :banghead:

So after looking on the internet for hours and not finding the elusive input sensor, I got off my ass and rolled underneath the cherokee. Low and behold, it seems as if the input and output sensor are actually the same style sensor.



The input is next the the bell housing midway up and the output is on the extension housing. Both of them have the same style connector. Without pulling them off, i can't tell if they are the same part. Can anyone confirm if they are infact the same part?

I believe they are the same- or at least I only see one part number listed, and no mention of input/output. Check RockAuto.com - they often have better prices than the stores, and sometimes more detailed info- OEM part numbers, other manufacturer numbers to cross reference, applications, etc.

SirFishouse,

The $300 item that you referred to is probably the Transmission Control Module, P/N 5601386AA. It is indeed a $300 item. Enter this part number in the red box search window.

http://www.autoecms.com/search/search.cfm

This P/N TCM was used in the '98-01 XJ if you want to search the bone yards for one. It's located under the dashboard - the little silver mother located just above the gas pedal.

As a note: The 'input' and 'output' speed sensors are the same part number for either position - a $38 item. If the tranny shop said the input speed sensor is bad they must of checked it with an Ohmmeter while spinning the transmission some way. The transmission has a 16 pole shaft gear inside the tranny that passes by the sensor, which generates a pulse voltage signal sent to the TCM. The output has a 4 pole output shaft gear inside the tranny that functions the same as the input.

A couple notes:

I agree with Tim_MN, the TPS does provide the TCM and the PCM with thottle plate position signals. If you can get someone that has a scanner that shows live TCM and PCM TPS outputs it will show if the TPS signal to the TCM is dead. The TPS is a problem child. It will create havoc with driveablity. Most people just shotgun a new TPS and see if it fixes anything.

I believe your '98 is the same as my '99, in terms of wiring. There is two ground posts for various functions designated as G106, one of which is TCM ground. The grounds are located below, and at the wire harnesses that go to the PCM on the left fender. If you think it's a TCM problem you should remove the ground bolts and inspect/clean the wire ends at the ground points and try it out before changing another part.

I would agree with Sidewinder here.

The input and output sensors on the 98 and later AW-4 are a reluctance/coil style sensor however, not a reed switch sensor like the older ones. Put your meter on voltage and watch as it spins, I'm not sure what you are looking for in terms of peak voltage but really an oscilloscope would be best for testing these sensors. You can also try just replacing the input speed sensor.

Another thing to keep in mind - since the issues are due to your behavior as a submarine captain, the sensor may not actually be at fault. Try disconnecting and cleaning the following connectors and see if it helps:
* connector for input speed sensor
* 7 pole black connector near transmission dipstick tube (this is the wiring harness to the input and output speed sensors as well as the transmission solenoids)
* bulkhead connector on firewall below the brake booster (toward the fender side)
* the connector at the TCU itself (the silver box mentioned by someone further up, above the gas pedal)

Since it was drowned... the TCU may indeed be at fault, which is actually fairly rare. Try a junkyard, you are looking for the part number mentioned by Sidewinder in post 9. Any 98 to 01 should have the one you are looking for; it should have 98 or later marked on its sticker (my guinea pig for a TCU project I am working on says 98M.) At most junkyards this part will run you under 50 bucks, my local yard charges me 10 or 20 depending on who is at the counter that day.

SirFishouse said:

He ran a diagnostic on my transmission and pulled up that it needs an input sensor on the transmission replaced. He says his parts dealer sells them for $300 bucks!!! I go to auto zone and they sell them for like $115. He installs the part and guess what..? I still have the same issue. My transmission still has the same error code. He tells me that I bought the output sensor instead of the input. I go back and try again.

Click to expand...

Which error code did he pull up?

What a Dildo.

First find a different transmision guy that knows what he's doing. Guessing and sending you out for parts and then blaming you is absolutely inexcusable. Did you ever get a check-engine light? If so, what codes were pulled.

It's highly unlikely that the speed sensors or the Trans computer (TCU) are at fault. Your hesitation and odd shifting are classic bad Throttle Position Sensor (TPS) symptoms. They really hate to get wet and power washing them is the easiest way to kill them.

I'd also second Kastein that you really need to start unplugging and cleaning up and connections to the tranny. Bad connections there could mimic bad solenoids, bad sensor inputs, etc.

Well i ended up putting in an order for another transmission sensor a couple days ago at my local autozone and installed it myself today. There is a very big improvement on the shifting, but I am still getting that hesitation. I think I'm just going to go for it and get a new TPS too.

1 Day Ago 11:06 Sidewinder CC
As a note: The 'input' and 'output' speed sensors are the same part number for either position - a $38 item.

Click to expand...

AHHHH! LOL, I saw a price online close to what i payed at autozone ($140 with tax) and thought that was the going rate. Oh well...

As for the error code, the old man was starting to clam up with the questions about part numbers. I figured the error code wasn't worth writing down. Come Monday though, hopefully his son will be back at work, and I can see about working out a deal with some other fixes i need. I have a serious-ish oil leak. I leak about a quart every 3-4 weeks.

I have legal insurance, and I asked the attorney about possible compensation for the messed up install. Basically, I was told that it wasn't really possible to pursue because, i was not returned the original part. There is no way to test whether or not the part was bad, so who is to say that the output sensor didn't need replacing too. Sucks...

kastein said:

Another thing to keep in mind - since the issues are due to your behavior as a submarine captain, the sensor may not actually be at fault. Try disconnecting and cleaning the following connectors and see if it helps:
* connector for input speed sensor
* 7 pole black connector near transmission dipstick tube (this is the wiring harness to the input and output speed sensors as well as the transmission solenoids)
* bulkhead connector on firewall below the brake booster (toward the fender side)
* the connector at the TCU itself (the silver box mentioned by someone further up, above the gas pedal)

Click to expand...

I dug up this picture a friend of mine had snapped with his camera phone. Yeah, I made a little mistake that day I was doing some rally racing in a freshly rained on construction site. Perfect 1 inch layer of water on level substrate for the parking lot that had not yet been paved. A friend of mine pointed out a nice stretch of water and I went for it. Turns out that that strech of water was the unfinished foundation of the building. I remember vividly the feeling of my car floating... and then the water began to rush in. Still paying for it years later, lol.

lawsoncl said:

It's highly unlikely that the speed sensors or the Trans computer (TCU) are at fault. Your hesitation and odd shifting are classic bad Throttle Position Sensor (TPS) symptoms. They really hate to get wet and power washing them is the easiest way to kill them.

Click to expand...

After about 4 years of driving with my check engine light, THE LIGHT FINALLY TURNED OFF TODAY!!!

The price of the TPS was not much at all, so I went for it. I don't know why, but the bolts for the sensor had loc-tite on them. I messed up two torx wrenches trying to get one of the bolts off, metal breaking off and everything. Luckily, I did not strip the bolt.

Anyways, after I installed the TPS and cranked up the engine, almost immediately, the check engine light turned off I have driven it about 20 miles since the sensor was installed, and I have had no trace of hesitation in acceleration.

I would really like to thank everyone who contributed to this thread. I am now driving a vehicle that is safe to take my son around in and not worry about getting T-boned at every intersection

After about 45 minutes of driving with my check engine light off, THE LIGHT TURNED BACK ON TODAY!!!
:flame::flame::flame:
I know I said the hesitation stopped, but it was still slightly present. I figured the computer was trying to adjust for the new sensor still. Well, on one of those hesitations, instead of letting off the gas, I punched through it. Light came on immediately.

I wonder if I should have let the computer take its course and be gentle on the driving, or if I have a short somewhere (which is very possible.) I have a two year parts warrenty on the TPS, so I'm going to swap it out again. I'll drive it gentle this time and see what happens.

Before you do anything else, read the DTCs and see if it tells you anything. You could have two issues causing you problems at once.

kastein said:

Before you do anything else, read the DTCs and see if it tells you anything. You could have two issues causing you problems at once.

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Yeah, you really need to get the codes check. Autozone does it for free, btw. When you check the codes, keep in mind that it also stores recent codes so may still see a TPS code even though that's been replaced already. Clear the codes after you check them, then if the light comes back on its will have the codes for and remaining problems.