2001 4R 2WD Error Code P 1120 and P 1121

I own a 2002 4R, bought new in late 2001 with no issues over the years but gave it to my wife to use. That vehicle runs great.

I purchased a used 2001 4R a year ago for work use and after a few months of ownership, I've had the issue with acceleration loss and/or just zero engine power other than idle. Initially my tech and I thought it was a loose connector on the TPS (or any other nearby connector). Now many months later, gathering knowledge from this forum (and other sources), I am a decision point. Here are my observations:

The issue occurs randomly after 10 +/- minutes of driving from a cold start, not associated with weather or other conditions. The "check engine" light comes on, and a later check with my Foxwell will show P1120/P1121.
When it does occur, I can drive with the pedal mashed to the floor, usually after a brief period of zero acceleration. This is the same as others have experienced.
If the engine is shut off and back on, this will usually restore full power/acceleration but with the "check engine" light until that code is erased.

So with the above in mind, is the TPS the device to replace first or am I looking at an ECM replacement? I've seen these YT guys with the same issue and after the TPS replacement, the demon returns.

Thank you.

 

Replace the TPS first. Only use a AISAN one. (W0133-2744128) Partsgeek.com sells it.

Toyota will only sell you the entire throttle body assembly. It is around $700 from an online Toyota parts dealer. You will get the Throttle Body and EVERYTHING attached to the Throttle Body (TPS\Pedal Position Sensor).

At 250k miles I got some goofy codes and weird acceleration and I just got the entire assembly. It fixed EVERYTHING that was causing weird driving issues. I bought my rig NEW in 2002 and she drives as the day I got her.

The only issue I see with replacing just the TPS, is that if the internal motors in the TB or the Pedal Position Sensor is bad, then there is no place to buy them. You have to go to TOYOTA and get the whole assembly. But for my issue, I actually think the TPS was the culprit.

The Pedal position sensor sits on the other side of the TB opposite the TPS and works much the same way.

This advice is for only 2001 and 2002 rigs as the earlier ones had different parts.

 

Thank you for that TPS part #. It has been ordered from Partsgeek. I should see it sometime next week. Stay tuned for more developments! Wish me luck!

 

Part arrived today, installed and started up. Engine went full throttle. Shut off. Tried a second time and the same thing.
I had read somewhere that this was due to the orientation of the inside mechanism but I don't see how that can be accomplished since it is spring loaded. What am I missing? Is there a procedure?

 

Replace with the old one and see what happens.

It's not supposed to go full throttle (red line). It may go up to 2500 RPM...which then it will take some time to relearn.

The only procedure that I read was to put the new TPS on and don't tighten it down fully. There are two screws holding it on. Loosen both where you can rotate it to where the RPMs near 1000 RPMs. Then the ECU should fine tune it after driving for a few days.

 

Negusm, good news! Had some spare time at work today. Reinstalled the new TPS (this time not rotating it 20 degrees CW-my error). Upon start up, engine now reved up to 2500 RPM and oscillated up and down for 15 minutes. Cleared the old error codes. Restarted-same thing. Made the adjustment/rotation on the TPS to get idle down to 1,000. The engine now settled down-no more oscillating up/down. Took a test drive. All good so far. Acceleration profile feels right (We have a 2002 4Runner we brought new back in late 2001-well cared for and thus, it runs great and a good vehicle to compare to). As time goes on, I'll give you and the group any updates needed but I thank YOU for the part # and suggestions!

 

Update on the TPS installation to solve (or to help solve) the loss of power issue and P1120/P1121:
After less than one day of driving tests over a period of one hour, power loss was experienced, a CEL illuminated and an error code appeared (P1120). Worth noting is the absence of code 1121 as in the past. Foxwell "Freeze Frame" readout says: "DTC that caused required freeze frame data storage".
What others have said on this forum is confirmed here: "Accelerator pedal position sensor is mounted on the throttle body and it has the 2 sensors to detects the accelerator position and a malfunction of the accelerator position’s own. The accelerator pedal position sensor is connected with the accelerator pedal by the accelerator wire and the voltage applied to the terminals VPA and VPA2 of the Engine Control Moduel (ECM) changes between 0 V and 5 V in proportion to the opening angle of the accelerator pedal.
The ECM judges the current opening angle of the accelerator pedal from these signals input from terminals VPA and VPA2 and the ECM controls the throttle motor based on these signals.
If the the P1120 code is stored, the ECM shuts down the power for the throttle motor and the magnetic clutch, and the throttle valve is fully closed by the return spring.
However, the opening angle of the throttle valve can be controlled by the accelerator pedal through the throttle cable"

I am coming to a conclusion that the issue may be the accelerator pedal position sensor which means (I believe) changing out the entire throttle body. But it is also worth noting that this issue manifests itself after engine warmup i.e. about 30 minutes (weather here today is around 70). Is it an intermittent cable harness? Is it the ECM warming up? I doubt it. I can say this: The acceleration improvement with the new TPS is good. Just have to figure out this loss of acceleration problem.

 

So here is the latest and the news is encouraging. There is a YT video talking about the same "limp mode" on the Lexus with P1120/P1121. It involves disassembly of the accelerator pedal position sensor and a re-solder of the 4 pins due to heat prostration and vibration over time (the same exact problem I have encountered). I don't know if the moderator will approve of the link but here it is:

https://www.youtube.com/watch?v=L7urUVFx4Dg&t=151s

On the 2001 4 Runner throttle body, the 4 Phillips screws securing the accelerator pedal position sensor are easily accessible. I removed the sensor, took it to the work bench and followed what the video did. The joints did look questionable. After resolder, it was put back together and reinstalled. I took about a 50 mile torture test on LA City streets for vibration and a longer drive on the freeway. I'm happy to report that I had zero power loss issues and no codes. Now only time will tell if this fix is permanent so no victory lap yet. But, the scenario lines up with my experience: The P1120 appeared in the past after warm up and was aggravated by vibration and/or exercising the throttle. If this "fix" holds up, I may go back and permanently repair the white cover over the soldered area.

 

I wish we could buy that part.

I know the TPS that you got was MIA for years and the Taco guys were screaming to be able to source it. They tried all kinds of options but mostly just scavanged junkyards. I'm hoping the Pedal Position sensor becomes available soon too.

I took apart the old Throttle Body I replaced with a new one from TOYOTA and it's quite a complicated thing inside. I can see why TOYOTA probably didn't want to screw with parts of it and just wanted to replace the whole unit. For someone like you with 2 or more issues with the assembly, the cost of labor and diagnosis will outweigh the part cost.

For me, the complete assembly fixed so many issues, that while I think the TPS was really my issue, it very well may have had other problems. So while I think it was worth it, $700 is hard for some people to spend.

If I were you, I'd scavenge the junkyards too for another PPS just for a backup if your fix fails.

 

Hello Negusm,
Perhaps some day that accelerator pedal position sensor will be available. But at least for today, the removal of the APPS from the throttle body was effortless and although the removal of the white dust cover was a bit scary, doing so with care does get you where you need to be. This is my own journey with this APPS and I don't recommend this surgery to anyone. They do it on their own. But I can tell you this: So far..., I have had zero "limp mode" issues.

Just to summarize my problems and how I came to this conclusion (with help from that Lexus YT video):
1) My "limp mode" issue basically started with a big bump in the parking lot of a truck stop in Lordsburg New Mexico in 2022. From that point forward, I've been wondering why something physical was apparently causing this problem. Wiring i.e. intermittent grounding or open circuit? Loose connectors on the throttle body?
2) Many efforts were made to tighten up all connectors on the throttle body and on the MAF. Nothing worked.
3) Was it the ECM? ECM was failing after a 30 minute warmup? Doubtful.
4) Going back to vibration as a catalyst for failure i.e. sudden "limp mode", I was leaning again towards something physical. Also, another important observation was that any extreme accelerator deflection that would be (possibly) stressing the APPS area was asking for an immediate "limp mode".
5) The "gift of the week" was that Lexus YT video showing the four possible failure points with cold solder joints. This made perfect sense (I've been working in television engineering/maintenance all my adult life). Getting into the APPS was a no brainer as I was out of ideas.

So only time will tell if this is the solution. Changing the TPS has also really helped with smooth and predictable acceleration, so thank you for that part #. Now hopefully, the cold solder joint "fix" will be a long term return to normalcy.

 

Man am I happy I found this thread. I have been having these same exact issues for about 4 months now and I'm starting to get annoyed lol. I replaced the TPS with that same AISAN pn and replaced the O2 sensors, cleaned throttle body and main air intake, check sensor voltages, everything! I've never soldered in my life but its worth giving it a shot before buying a new throttble body. Wish me luck The ECM circuit is mentioned in all of the codes I get, so I'm scared it might be the wiring itself...but I haven't read any examples of someone having to rewire so I'm still holding out hope.

PS when you go into limp mode, does your transmission shift poorly from 1-2 and 2-3? I live in the city so coming off a red light is terrible, I can feel the trans jump underneath me if I am slowly pulling forward, its not as bad if I'm pedal to the floor. I'm no trans expert but it feels like it shifts before it should, like the solenoid is not fully pressurized at the time of shifting. It is fishy that I performed my own trans flush only a few weeks before I started having these issues, but I followed everything on youtube and the manual to a T. Before I go into limp mode it shifts and rides beautifully. So imo if I had a mechanical issue with the trans, it would occur all the time, not just after entering limp mode.

I would appreciate any feedback, thanks guys!

 

C_hopp,

Welcome to this thread! Yes, when mine went into "limp mode", the transmission shiftily roughly with a thump. Now all of that is in the past.

Yes, I too had contemplated a wiring issue and a full throttle body replacement. I even considered an ECU swap. I am happy that I did not go down those routes.

I have roughly 1,000 miles since my APPS solder fix. All codes are gone, acceleration is good or even better now (perhaps also due to the TPS replacement) and gasoline mileage is above average (to me). No intermittent loss of power what so ever.

If you have any hesitancy with a soldering iron on this surgery, take the APPS unit to someone who has soldering experience and follow the Lexus YT video. I did not use a solder sucker and a re solder each of the four posts. I just touched them up with renewed solder flow. Maybe this will be a long term solution or maybe not but for a cold solder joint fix, I am confident.

We look forward to a good report once your APPS "retouch" is done and hopefully, you will have fixed your problem!

 

Thanks for the update. This is great info.

So few people ever post back that they've fixed the issue.

 

Negusm,

I guess I was lucky with that APPS fix. but this success has encouraged me to fix other things. one of which was the electric antenna. One job I'm not looking forward to is the transmission shifter bushing replacement. Stay tuned for that!

 

David, has your fix held up? I have the same vehicle, same issues, waiting on my new TPS to arrive but fear it may be the APPS. Thank you

 

Miguel, yes the "fix" has 100% held up. Absolutely zero error codes or loss of power. I have put on about 10K miles since the "fix" and all is well. If something goes wrong, this forum will be the first to be notified. If you repair yours in the same manner, you will be very happy I guarantee. I just hope what you are experiencing is the same as mine was originally.

 

Thats great! And I appreciate the update. For me it's still worth replacing the TPS first, the truck drives perfectly right now actually. The silver lining to this issue is that it forced me to remove and clean the TB, and address some leaks, torn intake boot, etc..... But I have a feeling the code will pop up again soon. Incidentally I came across some postings of ppl replacing our TB's with a newer model probably designed for the 02-04 Tacomas w/ the 3.4. It seems to be a couple of hundred bucks cheaper. I wonder if it's fully compatible with our 01 and 02s.

 

My apologies for the delayed reply. My APPS fix is still going strong. Not one code thrown yet.
Now one other thing that is a possible side effect of the time when the P1120 and P1121 codes were going and the transmission was shifting rough while "driving by wire". And that is, I suspected that during these times that the stress that the transmission was putting on the U-joints and drive train was eventually going to lead to pre-mature loss of at least one of the U-joints and maybe even the transmission. Indeed the front U-joint failed over the weekend to the point of severe vibration and grinding noise. After a lot of calling around yesterday, I finally found a driveshaft specialist up in Santa Clarita that could take the car in today and replace the U-joints. The front one was really torn up. But now it's all fixed up and the 4 Runner is smooth as silk.
The lesson here is: If you are having P1120 and P1121 codes and the transmission is shifting very roughly (kerchunking), you may end up with a stressed U-joint or two. I'm not a specialist in that matter but I'm just reporting my own experience $350 later.

 

Hey David, I've been reading this thread with interest, as my 2002 4Runner is exhibiting the exact same things. I'm about to replace TPS, but wanted to ask about the acceleration pedal position sensor. The part shown in the video is pulled off the ACTUAL pedal assembly inside the cab right?

EDIT: never mind, I realized it was in the engine compartment. I have it off and now I'm going to try and break that white piece off to access the solder points.

 

Hey David,

I read this entire thread and I am pretty certain I have the same issue on my 01 4Runner, actually for a few years now. I stopped using the car a couple years back due to this and finally got around to wanting to fix it and have been slowly doing work to it and this is the final step for me to be able to use it as a (basically) daily driver. I have been buying everything OEM from my local dealership (ordering online is cheaper, then doing store pickup) and somehow got lucky enough to be in the middle of this project during Black Friday/Cyber Monday as my dealer had a 25% off deal going on and was able to buy the entire throttle body assembly with new sensors for $415 so I had to pull the trigger. My question is, from your experience and assuming this is the same exact issue, do you believe a brand new throttle body assembly will fix this issue? At this point I am hoping this will be a 100% fix since this issue has been haunting me for a few years now and would like to use this car daily again without having to worry about it coming back and/or end up being something else. Just wondering if I am understanding that the APP is part of the throttle body and replacing the entire unit would be a solid fix. Would appreciate any advice.

 

It should. That tb assembly comes with both a new tps and pps.

If you still get those codes, you're looking at a wiring or ecm problem. There really isn't anything else that's going to cause those errors.

When you put the TB on, use a new gasket and let the computer relearn for 30 minutes or so. It will idle high for a bit.

 

negusm, appreciate the quick response! Will likely add the new TB (also got a new gasket as it is not included) in the next week and hoping that would be the fix. I do not have a code reader, do you happen to know if this is a code that would clear up on its own after driving multiple times?
I did see that I need to perform the idle relearn procedure when replacing the TB. I will update the thread with results after replacing and testing for a few days. Thanks again

 

Get. A. Code. Reader.

They are like $25 for the simple ones. You won't know what is broken otherwise.

Yes, it should reset after a while.

 

Just wanted to reply to this thread that I have had COMPLETE SUCCESS fixing my problems (same error codes thrown) but following the video to resolder the points. Car drives perfectly and has for a couple months now. THANK YOU SO MUCH!!!