Transmission shift hard when fan is on

You nailed it I got a used one for $100.00 plugged it in the car has never run better. :) I love this site.

Okay I have the 2.2 liter. Never had any problems until recently.

I can tell exactly when the problem is going to happen. Both fans on the radiator/AC come on and are at 100% running great. If in drive it hard shifts like crazy as if I am in some sort of limp mode. I can hand shift it and get stopped somewhere safe.

Now if I restart the car two or three times, the fans will on one of those tries will turn off and everything is fine, smooth shifting, the same perfectly good car as I have always known and will drive normally for a week perfectly. Then it does it again and I have to go through the routine of limping to a stop somewhere.

I got nothing, I have gone through the wiring harness, I hope to it is not a BCM maybe a TPS? Has anyone heard of this?

Absolutely no codes, not a single one. I did clean the battery terminals so I may have erased what was there. But even before then there was nothing there, no check engine light ever comes on.

Okay replaced the TPS today and drum roll please.

Wow, that changed things, over the past few weeks I have been super sensitive to every shift point and sound the car makes. One of the alternate problems was a random high idle at stop lights. So changed the TPS and what happened.

1) Transmission shifting is 15% smoother. Downshifts are normal.
2) More power, She moves like she should. Throttle is more responsive.
3) High Idle issues are completely gone.

As for (D) transmission hard shifts /limp mode/fans at 100% this will take time, but if we are good over the next couple of weeks I will say it is fixed. Replacing the TPS ($30.00 at Autozone) made a real and tangible difference.

Apparently the TPS can confuse the PCM and cause the car to go into a limp mode. It is scary and does not throw a proper code for it. People have dropped their transmissions to put in new pressure solenoids, only to have the problem crop back up.

Overall, If you are having the "fans on high/ hard shift" issue. I would say change your TPS (only $30.00 and easy to replace) and see if if things get better. Overall since this problem does not throw a code (or a proper one) it could not hurt and could save you a trip to the transmission shop.

I will update here if the problem persists with hard shifting. Or at least post if the problem has gone away for a minimum of two weeks.

I am working on a car that recently started shifting hard and getting code p0742.
Shifts hard from park to drive and all of the forward gears, like the accumulator was bad.

But after it is in drive and I come to a stop in D and take off again in D it shifts fine through 1-2 and 2-3.

But if I come to a stop and put it in park then D it will jump hard into D and go through the gear hard.

I replaced PC and TCC solenoid and it does not seem to stall when coming to a stop.
I just need to work with the hard shifting. Maybe I need to do a pressure test.

So far so good, none of the other problems I was having such as the high idle have shown up. The transmission problem was an intermittent one, so we are in wait and see mode. So far so good.

I only got that one code. There is no slipping in any gear. And 1-2 shift will clear up after a few take offs when it is left in D. Hard shifting comes when leaving park going into D and then followed by a hard 1-2 shift before it clears up again.

Well, it has been two weeks and not a single hiccup or problem since I replaced the TPS.

Bonus is that gas milage has gone up as well.

My transmission shifts very hard only when the cooling fan is running.

Hey there, I seem to have a similar problem. Did you do any tests on your old TPS to see if it was defective? (With a voltmeter testing for bad spots.)

Also, has the hard shifting come back at all?