There is also a sensor on the transmission (cant remember the name of it), that when it goes out, it causes hard shifting. Only issue is, the tranny needs to be dropped to get to it.

Transmission
 

Hey Beater, welcome to the forum! Please let us know if that relearn procedure works. There may also be a an adjustment to set the voltage of the sensor at closed throttle to 0.5 volts, not sure about your Ion. This may have nothing to do with your random trans. shift issues and harsh engagements. If you are checking codes with a code reader, it may not pull up trans codes. Sometimes the trans. controller will send a P0700 code to the eng. computer to let you know there are codes stored in the trans. controller. The computer is called a PCM (powertrain control module) but inside that module there is a separate controller for the transmission. In the old days, Dodge had two separate controllers, but since they work so close together, and share most of the data, it was more cost effective to combine the two controllers into one unit. With a scanner, not a code reader, you will need to access the transmission side and check for codes, current and history codes. I would imagine you will find a slip code, or a circuit code malfunction. When the trans. controllers sees a slip, based on rpm, input and output speeds, etc., the controller will boost line pressure to compensate for the slippage, to prevent further damage. That's why shutting of the key resets the trans. adapts, and it starts looking at data again. If it gets too bad, it will go into limp mode, usually second gear starts from a stop (no power on take off) and won't shift at all. Top speed of about 40 mph. The harsh engagements could be due to the TPS, or say...idle set too high, like a vacuum leak at the intake manifold. And erratic TPS data can effect shifting, but if turning the key off allows the trans. to start shifting normally again, you may have something else going on besides the TPS. I think Best to address the TPS, or APPS first, and go from there...

There IS a temperature sensor for the trans fluid. It looks a LOT like the ECTS. It's mounted on the front of the trans, under the ECTS as a matter of fact. A defective ECTS can and has caused a multitude of problems with the S series cars. DO NOT get one from Autovancerileynapa. Get one along with the pigtail (if you decide to replace them) from a Saturn friendly GM dealership. You want brass tipped, not resin.

I have yet to find one. I have 2 on the main highway by my house.
One told me my 03 is to old to work on, the other told me they didn't know Saturns were GMs.

Trans. Diag.
 

What??? Two GM Dealerships told you that, Goaliemo? Were you trying to get a temp. sensor, or have it diagnosed?

If it was the later, you can take your vehicle to any reputable repair shop. Now I'm not talking about Scooters Garage, Firestone or Wall Mart either, haha. Any good shop can check your vehicle for codes, and/or have the data for your sensors scanned. If they find a problem, you can order the part yourself from the Dealership, if they can still get it, or tell the shop service writer you want OEM (original equipment manufacturer) parts, or sensor installed. Most shops would rather use OEM parts, but usually with the customer, it's all about the cost of the part. OEM parts are most often more expensive than the aftermarket one's.

You can, if you like, Google shop's in your area, and read the reviews of past customers. When you find a shop, call them and see what they charge to read engine AND transmission codes. Then go from there. Just because they read the codes, or even do a diagnosis, that doesn't mean you have to have the repair done there too, if it is something you can do yourself. Yes, of course you could throw a part at it, like a TTS (Transmission Temp. Sensor) or an Engine coolant temp. sensor and it could very well fix the problem. Without a proper diagnosis, you may just be throwing money away that you could have spent to find the real problem in the first place...In my opinion.

In all my experience, I have never seen a bad temp. sensor (eng. or trans.) cause harsh transmission engagements from park to drive or reverse unless the engine idle speed is over 1,000 rpm's. A bad temp sensor will effect shift quality, but won't boost line pressure like a slip code, or electrical circuit code will...causing harsh engagements.

If you decide to have the codes read, let us know what they are. Perhaps you won't need a data scan for diagnosis. If there are no codes in the engine or transmission, you will most likely need some diagnostics performed.

Believe it or not, Scott, the early S series cars had a TAAT4 transmission that wasn't exactly the best on the market. A defective ECTS could and did cause shift problems with the trans. That along with a poorly designed valve body sent quite a few to the junkyard years ahead of their time. It's too bad too, because you can find replacement valve bodies online that take care of the issue. I did that with one of my coupes!

Taat4???
 

Hey there Charlie, thanks for the reply to my post! As you know, I'm new here and certainly not here to step on anyone's toes. You are correct Sir, the old TAAT's did have a host of issues with temp sensors, PRNDL switches, harsh delayed reverse engagements, EPC solenoids, poor line pressure, etc. I believe Billy stated his vehicle was a 2005 Saturn Ion 2, with a 2.2L. I'm pretty sure that is a 4T45E trans, not a TAAT4.

indeed

S car does not equal ION, and the trannys are of course different.
Let's get back on track.
-------------------------------

Any luck with the relearn, Beater?

Doh! I forgot about the trans change, Scott. Thanks for pointing that one out!

Beater?