Apparent APPS issue... P1121 code... now looking for replacement part and install photos (1 Viewer)

Joined
Jul 10, 2020
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Monterey, CA
Hi, 2001 LC here with 173,000 miles, 100% stock.
We were driving along this evening in the family truckster, almost home, going up a slight incline, when the check-engine light came on. Accompanied by a "clunk" sound (just one). From there, the car could move a little, but not enough to get through an intersection at the top of the hill. So, we put it into reverse. That was accompanied by another, louder, clunk, and a bit of a lurch backwards. From there,the car could shift into any gear (P, R, N, D, 2, L) but each shift was accompanied by another somewhat forceful clunk and a little bit of a lurch. The car could move forward or backward as needed, but with very little power. Kind of like if you were to try to go around in "Drive" but without applying any throttle.
I tried reversing up the hill and through the intersection (I know, I know, but this is a quiet area with nobody around)... again, not enough power to make it all the way through that steepest part of the hill right before our house.
Throughout this time, the engine was idling high, about 1500 RPM.
At this point, I backed down the hill, put it in Park and turned off the ignition. Waited a second, started it back up... and everything was fine. Drove back home without incident.
Went straight to the OBD2, which yielded a "p1121" fault code (APPS).
I used the OBD to clear the check engine light. It did not come back on.
I have put the car in and out of gear (drive and reverse) and puttered around in the driveway. Everything "seems" fine at the moment. But have not had the courage to drive it on the street. For that, I'll wait until daylight tomorrow at the earliest.
Maybe I should mention here that for the last few years there has been a very slight clunk when shifting from any gear into Reverse. We never did anything about it, but maybe we should have.

***EDIT July 10: I really appreciate the replies thus far. Upon further research, the APPS issue that I got from my OBD2 sensor definitely appears to be what is going on here.
At this point, I'm looking to get the replacement part (22060-50011) and am hoping not to pay retail (starting at $300+)... the only other alternatives I've seen so far, on eBay, seemed a little sketchy in terms of overseas shipping and whatnot.
Lastly, if anyone knows of any step-by-step installation photos that would be great! The three photos on this thread An illustrated guide to replacing your APPS - Part 1 are good but the 11-year-old link to the Picasa page with the rest of the photos is now dead. I have looked under the hood of our LC and I'm somewhat confident that I could install the new APPS without the rest of the photos... but I would feel a lot better if I could find those additional pics.
Thanks again...
 
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MJK

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When you were having this 'no power' problem, did the engine rev freely or not?

You checked driveline fluids (trans, t-case)? Level / color ok?

Edit: I see you added the P1121 code to the description. Check this thread out:
 
Joined
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Messages
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Monterey, CA
When you were having this 'no power' problem, did the engine rev freely or not?

You checked driveline fluids (trans, t-case)? Level / color ok?

Edit: I see you added the P1121 code to the description. Check this thread out:
Thank you for your reply!
I think it did not idle freely, but am not 100% sure.
Transmission fluid seemed OK, but am not sure about the transfer case fluid. I'll have to check that tomorrow. Note: To be honest, I'm not very knowledgeable about cars.
Yes, I discovered the thread that you linked, just a few minutes before I saw your reply. That all seems pretty consistent with what we experienced this evening.
I had noticed the p1121 fault code before I wrote my original post, but I had dumb-ly assumed that because I had never heard of an accelerator pedal position system, then it must be something minor and irrelevant to the seemingly major problem we experienced this evening. But now I see that was wrong, and this APPS issue might very well be exactly what's going on.
Thanks again.
Ironically, we sold our trusty old 2005 Prius just two days ago, after 15 years of service, so I really hope we resolve this new issue with our beloved family truckster soon. We do actually have another, newer car, so are doing OK for transportation... but still, terrible timing!!
 

MJK

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Arizona
If it is throwing the P1121 code, don't worry about the t-case fluid yet.

It seems likely you have APPS issue, which could explain the high idle and/or lack of throttle response. It would explain what failed you on the hill and also why a restart temporarily fixed it. If you shifted between reverse/drive at a 1500 RPM idle speed, that would certainly exacerbate any driveline clunks. I don't know if it explains the initial one or not.

The smaller clunks you've been having for years are likely unrelated. They could be worn hubs/axle teeth, shot diff bushings, driveshafts that need lubed and/or any number of other things that probably won't leave you stranded. I'd still get it looked at when you can.
 
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Eyedaho

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I just had something similar this evening after I put my rig back together from starter etc replacement. Mine was a P0120 on my '99, but there was basically no input when the throttle moved, which meant no power even though I was parked in the driveway. Mine ended up being that the sensor connection wasn't plugged in quite all the way on the bottom of the throttle body. Maybe you have something similar with a loose connection or sensor failure?
 
Joined
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Messages
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Location
Monterey, CA
If it is throwing the P1121 code, don't worry about the t-case fluid yet.

It seems likely you have APPS issue, which could explain the high idle and/or lack of throttle response. It could explain what failed you on the hill and also why a restart temporarily fixed it. If you shifted between reverse/drive at a 1500 RPM idle speed, that would certainly exacerbate any driveline clunks. I don't know if it explains the initial one or not.

The smaller clunks you've been having for years are likely unrelated. They could be worn hubs/axle teeth, shot diff bushings, driveshafts that need lubed and/or any number of other things that probably won't leave you stranded. I'd still get it looked at when you can.
Thanks again for your time and responses.
The more I read about the APPS, it all seems to check out with what happened this evening.
As for the hill we were driving on, it's a gentle incline for quite a while and then really steep for a very short distance (like 50 feet), and then goes back to a gentler slope for a few hundred feet and then we're home. It was that steep 50 that we couldn't do in the APPS issue's "limp home" mode. I'll keep researching, but this all seems to be consistent with what went down today.
 
Joined
Jul 10, 2020
Messages
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Location
Monterey, CA
I just had something similar this evening after I put my rig back together from starter etc replacement. Mine was a P0120 on my '99, but there was basically no input when the throttle moved, which meant no power even though I was parked in the driveway. Mine ended up being that the sensor connection wasn't plugged in quite all the way on the bottom of the throttle body. Maybe you have something similar with a loose connection or sensor failure?
Thank you for responding... In my research this evening I've seen some info about a loose connection in the APPS being a potential culprit. I'll try to look further into that possibility tomorrow.
 

flintknapper

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Thank you for responding... In my research this evening I've seen some info about a loose connection in the APPS being a potential culprit. I'll try to look further into that possibility tomorrow.

Possible, but the symptoms are classic APPS issue. Typically, turning the engine off and restarting will temporarily fix things, but it will do it again.
 
Joined
Jul 10, 2020
Messages
8
Location
Monterey, CA
Hi, 2001 LC here with 173,000 miles, 100% stock.
We were driving along this evening in the family truckster, almost home, going up a slight incline, when the check-engine light came on. Accompanied by a "clunk" sound (just one). From there, the car could move a little, but not enough to get through an intersection at the top of the hill. So, we put it into reverse. That was accompanied by another, louder, clunk, and a bit of a lurch backwards. From there,the car could shift into any gear (P, R, N, D, 2, L) but each shift was accompanied by another somewhat forceful clunk and a little bit of a lurch. The car could move forward or backward as needed, but with very little power. Kind of like if you were to try to go around in "Drive" but without applying any throttle.
I tried reversing up the hill and through the intersection (I know, I know, but this is a quiet area with nobody around)... again, not enough power to make it all the way through that steepest part of the hill right before our house.
Throughout this time, the engine was idling high, about 1500 RPM.
At this point, I backed down the hill, put it in Park and turned off the ignition. Waited a second, started it back up... and everything was fine. Drove back home without incident.
Went straight to the OBD2, which yielded a "p1121" fault code (APPS).
I used the OBD to clear the check engine light. It did not come back on.
I have put the car in and out of gear (drive and reverse) and puttered around in the driveway. Everything "seems" fine at the moment. But have not had the courage to drive it on the street. For that, I'll wait until daylight tomorrow at the earliest.
Maybe I should mention here that for the last few years there has been a very slight clunk when shifting from any gear into Reverse. We never did anything about it, but maybe we should have.

***EDIT July 10: I really appreciate the replies thus far. Upon further research, the APPS issue that I got from my OBD2 sensor definitely appears to be what is going on here.
At this point, I'm looking to get the replacement part (22060-50011) and am hoping not to pay retail (starting at $300+)... the only other alternatives I've seen so far, on eBay, seemed a little sketchy in terms of overseas shipping and whatnot.
Lastly, if anyone knows of any step-by-step installation photos that would be great! The three photos on this thread An illustrated guide to replacing your APPS - Part 1 are good but the 11-year-old link to the Picasa page with the rest of the photos is now dead. I have looked under the hood of our LC and I'm somewhat confident that I could install the new APPS without the rest of the photos... but I would feel a lot better if I could find those additional pics.
Thanks again...
***EDIT July 10: I really appreciate the replies thus far. Upon further research, the APPS issue that I got from my OBD2 sensor definitely appears to be what is going on here.
At this point, I'm looking to get the replacement part (22060-50011) and am hoping not to pay retail (starting at $300+)... the only other alternatives I've seen so far, on eBay, seemed a little sketchy in terms of overseas shipping and whatnot.
Lastly, if anyone knows of any step-by-step installation photos that would be great! The three photos on this thread An illustrated guide to replacing your APPS - Part 1 are good but the 11-year-old link to the Picasa page with the rest of the photos is now dead. I have looked under the hood of our LC and I'm somewhat confident that I could install the new APPS without the rest of the photos... but I would feel a lot better if I could find those additional pics.
Thanks again...
 

Eyedaho

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Boise, Idaho
Interestingly, it looks like new OEM entire throttle assemblies are available for under $450. Probably a good option for people dealing with similar issues if individual sensors are a couple hundred bucks.
 
Joined
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Interestingly, it looks like new OEM entire throttle assemblies are available for under $450. Probably a good option for people dealing with similar issues if individual sensors are a couple hundred bucks.
Yeah, I noticed that too last night. It does seem like a good option, especially if the throttle body has potential to be an easy DIY installation. Do you happen to know if that's the case? I've had trouble finding any info on self-installing a whole new throttle body.
 

MJK

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Amayama.com has 22060-50011 for about $200 delivered. I've had good luck with them and Partsouq.com in the past.

If the throttle body is 22030-50142 (?) that looks like it is $800 new.
 
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Eyedaho

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Messages
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Yeah, I noticed that too last night. It does seem like a good option, especially if the throttle body has potential to be an easy DIY installation. Do you happen to know if that's the case? I've had trouble finding any info on self-installing a whole new throttle body.
There's some stuff in the FSM about adjustments for individual components, but I'm guessing the OEM replacement would already be adjusted? I had mine totally removed this week, and it was easy. Just the two cooling lines, vacuum line(s) and a couple electrical connectors. It's held on with two bolt and two nuts, and just pulls right off of the front of the manifold. It would be like a fifteen minute job on its own I think. The replacement looks like it comes with new cooling lines, so I think you'd just want a fresh throttle body gasket, which is like $15-20.
 
Joined
Jul 10, 2020
Messages
8
Location
Monterey, CA
Hi, 2001 LC here with 173,000 miles, 100% stock.
We were driving along this evening in the family truckster, almost home, going up a slight incline, when the check-engine light came on. Accompanied by a "clunk" sound (just one). From there, the car could move a little, but not enough to get through an intersection at the top of the hill. So, we put it into reverse. That was accompanied by another, louder, clunk, and a bit of a lurch backwards. From there,the car could shift into any gear (P, R, N, D, 2, L) but each shift was accompanied by another somewhat forceful clunk and a little bit of a lurch. The car could move forward or backward as needed, but with very little power. Kind of like if you were to try to go around in "Drive" but without applying any throttle.
I tried reversing up the hill and through the intersection (I know, I know, but this is a quiet area with nobody around)... again, not enough power to make it all the way through that steepest part of the hill right before our house.
Throughout this time, the engine was idling high, about 1500 RPM.
At this point, I backed down the hill, put it in Park and turned off the ignition. Waited a second, started it back up... and everything was fine. Drove back home without incident.
Went straight to the OBD2, which yielded a "p1121" fault code (APPS).
I used the OBD to clear the check engine light. It did not come back on.
I have put the car in and out of gear (drive and reverse) and puttered around in the driveway. Everything "seems" fine at the moment. But have not had the courage to drive it on the street. For that, I'll wait until daylight tomorrow at the earliest.
Maybe I should mention here that for the last few years there has been a very slight clunk when shifting from any gear into Reverse. We never did anything about it, but maybe we should have.

***UPDATE July 10: I really appreciate the replies thus far. Upon further research, the APPS issue that I got from my OBD2 sensor definitely appears to be what is going on here.
At this point, I'm looking to get the replacement part (22060-50011) and am hoping not to pay retail (starting at $300+)... the only other alternatives I've seen so far, on eBay, seemed a little sketchy in terms of overseas shipping and whatnot.
Lastly, if anyone knows of any step-by-step installation photos that would be great! The three photos on this thread An illustrated guide to replacing your APPS - Part 1 are good but the 11-year-old link to the Picasa page with the rest of the photos is now dead. I have looked under the hood of our LC and I'm somewhat confident that I could install the new APPS without the rest of the photos... but I would feel a lot better if I could find those additional pics.
Thanks again...
***UPDATE July 16: Thanks again to everyone who replied.
To date, I have:
1) Cleaned out the throttle body,
2) Cleaned the MAF sensor, and
3) Put a dab of dielectric grease in the APPS electrical clip.
No recurrence of the APPS issue so far. We'll see what happens!
 

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