[SAFETY] Inspect accelerator assembly

Please do not panic. I want to give the community a 'heads up' on a problem found with an accelerator assembly that had a bent follower arm:

As you can see, the arm from the potentiometers is bent so the nylon bushing is angled into the slide mechanism. From another angle:

I noticed it because after cleaning the potentiometer, I still had an abnormal resistance slope on the lower one. I also noticed that a full deflection, the 'spring' was weaker because the nylon bushing was beginning to jam into the slide mechanism. So I removed the potentiometer:



Once I straightened the arm so it made a 90 degree angle, the accelerator assembly worked smoothly and the resistance anomaly went away. I'm putting the repaired assembly in my Prius for field testing.

INSPECTION

I would recommend doing a quick inspection of your accelerator assembly. You will need someway to lay on your back and possibly a flashlight to see the assembly:


Lay down and shift yourself so you can see the accelerator assembly and the encoder shaft, the NHW11 uses dual potentiometers and the NHW20 uses a Hall effect device:

If the encoder arm looks like this, there is no problem. But if it looks to be at an angle, plan to take it into Toyota and ask that the problem be fixed. Alternatively, you can remove the accelerator assembly and try to fix the problem by bending the follower arm to be at a 90 degree angle.

I have no idea what a Toyota Service department will do since I am well beyond any Toyota warranty. However, I suspect after I send a note to Toyota America and a copy to the NHTSA this will be fixed.

If you have it, with the car powered off, press your accelerator to the floor and lift off. If the accelerator returns, do it several times, pushing hard each time, and if it always returns, you can probably drive the car safely to the dealer. If it sticks or 'feels funny,' I would not recommend driving the car if there is any chance you might have to stomp on the accelerator. For sure, get the accelerator assembly repaired.

Now what happens if Toyota gives you a 'ration of sh*t?' I would recommend having a copy of this note and ask to see the manager. Ask the manager his name and the owner of the dealership so if there is a run-away, the lawyers will know who refused to repair the defective part. Be polite but get their names and phone numbers. Make sure they have your contact information too, leave the note and ask their general manager to look at it and go home.

Now document the bent part with a photo and post your message to this thread with your mailing address contact information and that of the dealer. I suspect in a very short period of time, they will contact you and offer the repair for free. Be sure it includes them towing the car from your home to their shop and return or taxi fare for you to pick it up ... and for your time and effort, ask them to throw in having the transaxle oil changed and a sample of the old oil.

Did I mention, DONT PANIC. This is a potential problem and easily repaired once you know about it. But this would be a good time to 'do the right thing.'

Bob Wilson
625k Inc.

ps. Located on the backside of the accelerator pedal is: 78111-35030. Marked on the side is a three digit "198" and no other manufacturing code or stamp.

 

I have a 2003, 2001-03, NHW11 model. I have not seen an NHW20 accelerator assembly and do not know if they use the same mechanical configuration. This is a mechanical problem due to the angle of the nylon follower that can jam in the slider.

If you have trouble reaching the area, you might take a digital camera with flash and try to take photos of the area. It may take a few until you can be sure you have a photo of the mechanical part.

Does anyone have a photo of an NHW20 accelerator assembly?

The following comment was posted in the YahooGroup, Prius-stuff

It wasn't the bent, nylon cam follower arm that clued me to the problem. When it began to 'jam' in the slider, it would put enough stress on the potentiometer that I was seeing an abnormal resistance slope:


After correcting the bent follower arm:


I tend to have a narrow vision when looking at a problem: (1) diagnosis, and (2) fix it. But I realized after the fact that fixing the cam follower arm means that other than the photographic record, the original failed part no longer has the problem. All I can do is document what I found with the facts and data and ask folks to check their own vehicles.

If someone else finds a similar bend in the cam follower arm, this will be exactly the case needed to escalate the problem. But I was one person removed from the original owner and worse, I corrected the problem. This means we no longer have physical evidence of the problem and I'm not about to 'break it'. We need to find one that is already broken.

Now I do not know if the NHW20 uses the same accelerator mechanical configuration. To me it looks as if the designer needed a wider swing of the potentiometer and the cam follower mechanism does that. It works perfectly as long as the nylon cam is at a 90 degree angle relative to the slider. But when it goes 'off angle,' it can jam or put enough stress on the potentiometer to cause an abnormal slope in resistance curve.

Bob Wilson

 

I just checked a 2008 Prius accelerator and it is a different design with the interesting bits enclosed in a plastic housing. Since it was not my car, I thought better about taking a screw driver to it. However, the pedal arm is now a steel web, not the earlier rod, so hopefully the guts don't run the risk of a cam-follower problem.

This is just a problem that NHW11 owners should check.

Bob Wilson

 

Sorry, no. It had been sent to me as part of an accelerator refurbishment, a returned core. I hadn't really noticed it until after cleaning when there was a non-linear resistance on the lower pot. I went into 'debug' mode and had the "What is this?" moment.

Bob Wilson