TPS limp mode, now OK, fix or not?

[hoser]

Rusty_tlc did have a good thought about this: Since the APPS is being controlled by the accelerator pedal shouldn't the cruise control function as a crude throttle in an emergency situation such as when the APPS goes south? Good question: Next one that has their APPS go south give it a try and report back ...please .

Good idea but most vehicles have a minimum and maximum speed at which you can engage the cruise control. Ever try to set the cruise control at 100 mph? hehe. So if you can't even get up to 35 mph (I don't know the exact speed), the CC won't engage. Maybe the better band-aid is an in-cabin hand throttle wheel.

Question: Didn't the LC go with a drive by wire set-up on the later models (year?). If so wouldn't this eliminate the need for the APPS altogether?

Slee's guide says "2003 The throttle position sensor was changed to a no-contact unit" but there might have been a change/superceded replacement part earlier than that. Sincity100?

 

[SINCITY100]

Slee's guide says "2003 The throttle position sensor was changed to a no-contact unit" but there might have been a change/superceded replacement part earlier than that. Sincity100?

I will check tomorrow on the TPS/APPS units, but I am sure that the entire TB assy has been upgraded to a newer part# on the earlier (98-99) 100 models.

Yeah.. a recall would be nice, but unless an item is mandated by the National Traffic Safety Commission , you usually wont see an actual "recall" from a vehicle manufacturer.


BTW.. I was just blowing smoke when I asked if I should trade in my 100 for a Tacoma , its just frustrating to me seeing so many different failures on the 100 models that shouldnt have occurred at all ( even though the newer-generation Tacoma has proven itself to be 99% bulletproof.. even by Toyota standards ! )

 

[SINCITY100]

Oh yeah.. I forgot.

parts to carry list will always grow larger with vehicle age, you know that lee.

Geez !! Can`t I get fired up ONCE in a while Loud ??

 

[rusty_tlc]

Lee, I'll be calling you tomorrow.

I think I'll be replacing the APPS, TPS, O2 sensors, and the PS front window regulator that took a crap in DV this weekend.

comment after the window got stuck half way down was "I guess these weren't designed to be used like this."
She was a trooper, we had a pretty high pass to go over on the way out and it got damn cold. She laughed it off and pulled a bienie hat on.
If the APPS had failed on our trip last week we would have been screwed.

Pulling the APPS took about 10 or 15 minutes. All you need is a 10mm socket and a phillips. I may give the cruise control throttle fix a try.
I'm also going to give fixing the APPS a whirl.

 

[Travis351]

Good idea but most vehicles have a minimum and maximum speed at which you can engage the cruise control. Ever try to set the cruise control at 100 mph? hehe. So if you can't even get up to 35 mph (I don't know the exact speed), the CC won't engage. Maybe the better band-aid is an in-cabin hand throttle wheel.

Slee's guide says "2003 The throttle position sensor was changed to a no-contact unit" but there might have been a change/superceded replacement part earlier than that. Sincity100?

My cruise will let me set it at 25MPH and up. Haven't tried it at triple digits though. Maybe those of us addicted to cruise control save wear and tear on the TPS?

 

[rusty_tlc]

My cruise will let me set it at 25MPH and up. Haven't tried it at triple digits though. Maybe those of us addicted to cruise control save wear and tear on the TPS?

It might save wear on the APPS. The TPS still moves, it monitors the throttle control motor shaft. I think the cruise uses the throttle position motor to govern speed, which is why I was thinking you could use cruise to by-pass a failed APPS.

 

[rusty_tlc]

After looking at the schematics of the TPS and APPS I can see where it might cause a CEL then go away for miles and miles. All it would take is a bit of crud on the potentiometer wiper. It makes sense that Toyota would go to a rotary digital encoder in later designs.

I tested my APPS tonight and it failed open. Either something is wedged between under the wiper holding it off the resistor, or one of the wires is open.

 

[SINCITY100]

Lee, I'll be calling you tomorrow.

I think I'll be replacing the APPS, TPS, O2 sensors, and the PS front window regulator that took a crap in DV this weekend.

Sounds like I`m gonna have to make you a "package deal" on this order !

After looking at the schematics of the TPS and APPS I can see where it might cause a CEL then go away for miles and miles. All it would take is a bit of crud on the potentiometer wiper. It makes sense that Toyota would go to a rotary digital encoder in later designs.

I tested my APPS tonight and it failed open. Either something is wedged between under the wiper holding it off the resistor, or one of the wires is open.

Rusty... Spress... Are you looking for jobs by any chance ? You guys would be invaluable in our service department... Thank God you just tell me what you need and dont ask me to figure it out for ya !!

 

[hoser]

Rusty_TLC, when the APPS fails, are you dead in the water or is there a fail safe, crawl home mode? And if it can crawl home, how slow is slow?

 

[spressomon]

Rusty_TLC, when the APPS fails, are you dead in the water or is there a fail safe, crawl home mode? And if it can crawl home, how slow is slow?

No crawl on his. I think the TPS gives you a second opportunity to get along...but not the APPS. That's why I'm buying one for "the kit" .

 

[hoser]

Looks like we need to start a new thread... "What to put in the spares kit."

 

[spressomon]

Looks like we need to start a new thread... "What to put in the spares kit."

Yeah maybe...but the front diff issue just raised a bunch o'nay sayers . And since it appears the APPS failure might be even more rare than the front diff failure it might go over like a lead balloon . But since my rig takes me into some fairly remote/desolate places on a regular basis I need to shore up my odds...so I'll be adding this to my kit since limping home on a failed APPS doesn't work per rusty.

 

[i4c4lo]

I had this issue for a long time, I even got a OBD II Scanner because of it. I've replaced both pieces.

In a pinch - take out your EFI fuse for a few minutes and it will reset or you can unplug your battery.

What you don't want is merging on the freeway and have it fail and you can't accelerate to merge or get out of the way.

 

[i4c4lo]

Hoser,

To add to your "what to put in the spares kit" is the kind of fuses we have - the small bladed ones. The 80's and most other cruisers come with the larger bladed type.

 

[spressomon]

I had this issue for a long time, I even got a OBD II Scanner because of it. I've replaced both pieces.

In a pinch - take out your EFI fuse for a few minutes and it will reset or you can unplug your battery.

What you don't want is merging on the freeway and have it fail and you can't accelerate to merge or get out of the way.

Amando: Your tip works for the APPS?

 

[Landpimp]

mine was the APPS range problem, there is another code for APPS failure(this is the one it looks like is seen more often), I was able to limp but then it "fixed" itself

No crawl on his. I think the TPS gives you a second opportunity to get along...but not the APPS. That's why I'm buying one for "the kit" .

 

[spressomon]

mine was the APPS range problem, there is another code for APPS failure(this is the one it looks like is seen more often), I was able to limp but then it "fixed" itself

I thought your issue emanated from the TPS? Which code did your's display?

PO120: TPS
PO121: TPS

P1120: APPS
P1121: APPS

 

[rusty_tlc]

Rusty_TLC, when the APPS fails, are you dead in the water or is there a fail safe, crawl home mode? And if it can crawl home, how slow is slow?

I had it to the floor and barely made it up the driveway. That was nerve wracking, I was afraid it would suddenly take off through the door.

 

[NMuzj100]

I had it to the floor and barely made it up the driveway. That was nerve wracking, I was afraid it would suddenly take off through the door.

I am pretty sure this is why resetting the "limp mode" requires a shut down.

If Sin can confirm that there are updated parts available then replacement makes a lot more sense. But replacing a poorly designed part with a single intermittent failure for an identical poorly designed part with no performance history is less appealing.

 

[rusty_tlc]

I am pretty sure this is why resetting the "limp mode" requires a shut down.

If Sin can confirm that there are updated parts available then replacement makes a lot more sense. But replacing a poorly designed part with a single intermittent failure for an identical poorly designed part with no performance history is less appealing.

Replacing a part with 145K miles on it with a new part makes sense to me. In my case it isn't an intermittent failure, as I mentioned earlier it fails the FSM bench test.

I don't think the part design is at fault. I think it is a system design problem. There really shouldn't be a part with that low of a service life in such a critical application unless there is a redundant or back up system. This is why I said I wouldn't be surprised if Toyota went to a rotary encoder on later models.