TPS and Tranny cant get along under load!

[TacosnBeer]

I have a 98 GMC... orig a 305 but it was swapped with a carbed 350 and a B&M Throttle Position Sensor to talk to the computer/tranny. It runs, drives, and shifts perfectly for flat ground and not getting into it.

Under load, like hard pedal or while climbing a hill, it seems like the overdrive is acting weird shifting up and down... not sure if it is in conjunction with the shifting but my gauges tend to bounce around at the same time.

I have a lot of codes for things that arent hooked up but specifically, I do get P0122 GEN TPS LOW Circuit Input.

It has done this since I got the truck soon after the swap... one of the issues the PO never worked out.

Could this be the problem? What can I check to find out why I am getting that code? Could it be the TPS is bad?

 

[RichLo]

is it only under constant load like when towing up a hill or is it also when under intermittent load like passing a car?

If its towing, it may just be that you need to keep it in 3rd for those occasions

 

[TacosnBeer]

is it only under constant load like when towing up a hill or is it also when under intermittent load like passing a car?

If its towing, it may just be that you need to keep it in 3rd for those occasions

Its under any load... heavy throttle or driving up a grade. I live up a mountain and not the way down, if I drive normally.. its fine. On the way home, it is all over the place. If I am hard on the gas pedal it shifts funny too.

It is something to do with the TPS or overdrive I think... I don't know but it sucks and I want to figure it out. I have tried to adjust the cable on the TPS a little both ways and it doesn't help it any. Just makes the shift points all over the place.

 

[WB23]

Having the same problem on my 98

 

[thegawd]

ya I second that! use 3rd when towing or under heavy load when going up a hill. this one thing dictates how long a tranny will survive. haha also do you have a cooler? when that tps code is activated you need to find out why.

I assume that the tps can still be read by the vehicles computer since it appears that the original 4L60E is still there and functioning. therefore you can plug an obd2 scanner in and do a simple test of the tps. my cheap innova shows the tps in graph form. the line should rise smoothly as the throttle is opened. if there are any breaks, jumps or any anomalies then it has failed. the vehicles computer wont always set codes for a failed TPS because it just believes the incorrect data and makes adjustments accordingly.

Al

 

[TacosnBeer]

ya I second that! use 3rd when towing or under heavy load when going up a hill. this one thing dictates how long a tranny will survive. haha also do you have a cooler? when that tps code is activated you need to find out why.

I assume that the tps can still be read by the vehicles computer since it appears that the original 4L60E is still there and functioning. therefore you can plug an obd2 scanner in and do a simple test of the tps. my cheap innova shows the tps in graph form. the line should rise smoothly as the throttle is opened. if there are any breaks, jumps or any anomalies then it has failed. the vehicles computer wont always set codes for a failed TPS because it just believes the incorrect data and makes adjustments accordingly.

Al

I don't even know where to start to trouble shoot at this point. yes, the tranny is connected to the computer so, the code pops. I have an innova reader too... never saw the function to see the graph for TPS... I have to look into that.

Even on flat ground, if I am doing like 50+ and its in OD, it will bounce around a little - but, like I mention, up a hill or harder pedal... it feels like it goes in and out of OD.

What can I check? Should I just take it to a tranny shop? (Ugh)

 

[thegawd]

hit Live data and scroll down to the tps and hit the arrow button to enter.... then you can see the graph. you dont need the truck running for the test but the key has to be in the run position. then you don't have to redline the engine to completely open the throttle. be aware that it will drain the battery though...

You must be registered for see images attach

 

[TacosnBeer]

hit Live data and scroll down to the tps and hit the arrow button to enter.... then you can see the graph. you dont need the truck running for the test but the key has to be in the run position. then you don't have to redline the engine to completely open the throttle. be aware that it will drain the battery though...

You must be registered for see images attach

Mine is the INNOVA 3100e - I looked at the manual and it doesn't have the live function option.... oh well. That is a super cool function though.

 

[Dropped88]

You also Dont have a MAF and it uses that for calculated load which messes with shift points and pressures

 

[TacosnBeer]

You also Dont have a MAF and it uses that for calculated load which messes with shift points and pressures

You are absolutely correct. There has to be a way to bypass this for my set up though. I am sure I am not the only one with a carb motor and factory computer control tranny. I guess that is the information I am looking for. Hopefully, this isn't damaging my transmission right now.