Throttle Position Sensor (TPS) Adventure

[Philbo]

Hmm I will have to try tomorrow and see.

 

Bu I have had where I go to drive and it is working then while cruising I can tell when it cuts off because the RPMs jump back up.  But have never gotten a code for it.  The only TCC code I've ever gotten was the one that came on when I got the E022 for the TPS. (The two could be unrelated) 

 

Strange.

[Padgett]

Sounds like something is telling it to shut off. One of the things that can is if it thinks the TPS goes over 50% (about 2v) This should not happen in level cruise at any sane speed. It also turns on around 50 and off a 45ish. I'd need to know what prom you have to know the precise speeds.

[Philbo]

7 hours ago, Padgett said:

Sounds like something is telling it to shut off. One of the things that can is if it thinks the TPS goes over 50% (about 2v) This should not happen in level cruise at any sane speed. It also turns on around 50 and off a 45ish. I'd need to know what prom you have to know the precise speeds.

Hmm the TPS is definitely not reading 2v at curise. Probably is more like 0.8V. Also based on the diagnostic, it starts indicating the TCC for me at 40mph, which seems low.

[Philbo]

Ok the E039 (TCC Circuit) code did come back but was only listed as historic.  Maybe it has come on in the past and I never noticed because it has not caused the check engine light to come on.

 

I drove this morning in diagnostic mode and learned a couple things. The TCC is being called for at speeds as low as 39mph.  It did work again for the firs about 8 min of driving and operated consistent with the indicator (med light) on the diagnostic (including coming on at 39 mph).  Then it ceased to work but diagnostic continued to show that it was calling for the TCC. It ran in closed loop for the whole trip into work this morning.

[2seater]

Regarding the mph where the TCC will engage: I am pretty sure I saw something in the FSM that stated it may engage in third gear or even second gear depending on the programming. I can’t check that on mine because I have modified the lockup point. 
When it is working, what is your rpm at highway speed? With the standard 2.97 axle ratio it should be about 2000rpm at 72mph

[Philbo]

5 minutes ago, 2seater said:

Regarding the mph where the TCC will engage: I am pretty sure I saw something in the FSM that stated it may engage in third gear or even second gear depending on the programming. I can’t check that on mine because I have modified the lockup point. 
When it is working, what is your rpm at highway speed? With the standard 2.97 axle ratio it should be about 2000rpm at 72mph

Hmm how did you change your lockup point?

 

And 2000rpm is about right for those conditions.

[Padgett]

Assuming an ATYH bin (90) here is the stock table.

 

To extract and modify requires a bunch of stuff, stock PROMs are getting to old to reflash (do not reliably erase) so use new 27C256s and a Moates adapter. Not hard once you have everything.

 

[Philbo]

Interesting.  So the 39 mph seems correct then.

 

I will have to do some flipping through the manual about the TCC. I am guessing it will boil down to a bad actuator.

 

Honestly though, I don't really mind driving without it.

[Philbo]

1 hour ago, Padgett said:

so use new 27C256s and a Moates adapter.

Btw, where would one acquire said new PROM and adapter?

 

This is getting into uncharted territory for me.

[Ronnie]

49 minutes ago, Philbo said:

Honestly though, I don't really mind driving without it.

Most of my driving is through the mountain roads of East Tennessee for pleasure. I have a switch on my car that allows me to turn off the TCC to prevent it from locking up. It think it makes the car feel more responsive without the converter locked. If I drive on a major road or Interstate where I cruise at speeds over 60 I flip the switch and allow the converter to lock up.

[2seater]

1 hour ago, Padgett said:

Assuming an ATYH bin (90) here is the stock table.

 

To extract and modify requires a bunch of stuff, stock PROMs are getting to old to reflash (do not reliably erase) so use new 27C256s and a Moates adapter. Not hard once you have everything.

 

Nice chart! Nothing better than an illustration to clarify things. 

 

You are way ahead of me on the programming front and agree completely about old EEPROMS and have done as suggested. Adapter in place and just change the actual chip, or operate engine from a laptop, until a satisfactory tune is arrived at before trying to load into the stock piece

[2seater]

2 hours ago, Philbo said:

Hmm how did you change your lockup point?

 

And 2000rpm is about right for those conditions.

I did a quick and dirty program change in the chip to not allow lockup below 55mph. It does look like you may have an actuator failure impending, likely from heat. Did you remove and clean the contacts in the big plug at the top front of the trans. as suggested by Ronnie?

[Philbo]

1 hour ago, Ronnie said:

Most of my driving is through the mountain roads of East Tennessee for pleasure. I have a switch on my car that allows me to turn off the TCC to prevent it from locking up. It think it makes the car feel more responsive without the converter locked. If I drive on a major road or Interstate where I cruise at speeds over 60 I flip the switch and allow the converter to lock up.

I would be interested in learning how you did this some day.

[Philbo]

1 hour ago, 2seater said:

Did you remove and clean the contacts in the big plug at the top front of the trans. as suggested by Ronnie?

Not yet.  That is the next step.

[Padgett]

All of this was a lot more common a few decades ago, many were interested in reprogramming ALDL cars but since OBD-II took over, interest has been dropping and Tuners emerged. I have a Pocket Programmer III USB but not sure these are still available. Are other PROM readers/programmers but need to make sure a 27C256, 27C512,  and 2816 are in their capabilities. Understand some use flash memories but never bothered. Flash is good for on-the-go tuning.