Wheel Alignment

The rear wheels should have a certain amount of negative camber (they should lean towards the center of the car a bit). The red indicates your left rear doesn't lean as much as it should.

At -0.8 deg, it is only 0.2 deg beyond the -1.0 to -2.0 deg lean in spec.

The rear camber isn't normally considered adjustable by Toyota but can be adjusted with the use of shims. You could get it adjusted be a competent shop, but I doubt it will adversely effect tire wear or cause other problems as is.

 

The alignment is fine. My main concern is that the Hunter printout is not showing that a zero-point calibration was done using Hunter code link.

The effects of not doing a zero-point calibration can vary widely. I had my steering wheel reentered recently and without doing a zero-pt calibration the steering suddenly started feeling unusually sloppy. I just did a zero-point calibration tonight and now the steering is much more solid...not sure why.

 

How do you perform the zero point calibration?

I had my alignment done by Hunter. They did not provide a printout, but I was there and they did not do anything other than adjust the tie rod.

The Hunter alignment video instructs the techs to perform the steering angle sensor reset, so I don't know why they didn't do it on OP and mine.
Hunter Alignment Racks Are Now Able to Perform Zero-Point Calibration Without Factory Scantool | PriusChat

 

Zero point calibration is used for the power steering, and the VSC. The VSC needs to know the angle that the steering is at so that it can calculate what each wheel speed should be calculated against each other. If the car begins to slide in a bend the mismatch in wheel speed can be used to calculate along with the yaw sensor which wheel or wheels to brake to bring the car back into line.

John (Britprius)

 

Thanks John, Do you know the steps to perform the procedure?

My car took a direct hit on the tire, got new tie rods, but now the wheel is slightly off center after alignment. The zero point calibration was not done and I suspect that is causing my skid warning to alarm.

 

If the wheel is off center the alignment needs to be re done. One track rod needs to be shortened the other lengthened by the same amount until the steering wheel is straight for straight running on the road. Do not re position the steering wheel to accomplish this as this can damage the clock spring and will further upset the zero point calibration. Plus you will end up with more steering lock in one direction than the other.
The zero point calibration can be done with Techstream or with suitable alignment equipment.

John (Britprius)

 

So there is no DIY procedure to reset the steering angle sensor?
The shop couldn't align the steering wheel b/c the tie rods were rusted tight on one side. I suppose I could replace them. Even though it's a Hunter shop, they don't have the Codelink to reset the calibration. I was hoping to find a DIY method for zero-point calibration, since I know it exists for other vehicles.

 

Maybe John can comment on this, but there's really no point to reset the calibration without getting the alignment correct and straightening the steering wheel (via the tie rods). Maybe you will get lucky and the correct alignment will have the zero point correct (or at least close enough to stop the skid alarm for the time being). Even if it did, it still would be worth having done after the parts are replaced, as I am one who was saved from a sure accident in the snow by this system, working properly.

 

Thanks Joe, I had thought that perhaps replacing the other tie rods and getting the steering straight might solve the skid alarm problem (IF it lines up exactly where it is calibrated). But I don't know how finicky the sensor is. Right now the alignment is great, but the steering wheel is off by just 5 degrees or so. Not enough to bother me, but apparently enough to set off the alarm. If I could DIY the sensor reset and solve my problem, at least that would let me know for certain what is causing the alarm. If I can't, I'll just replace the rusty tie rods and then take it to Toyota for an alignment and calibration.

 

I came across this article:

Alignment & Suspension Specs: 2001-2009 Toyota Prius: Brake and Front End

It mentions something about disconnecting the negative battery terminal to reset the sensor, so I tried that. I parked the car on flat, level road, made sure my wheels were lined up straight, unhooked the black cable from the trunk battery for a few minutes, hooked it back up and what do you know, it worked! It's been a few days, I've driven about 30 miles and the skid alert has not come back.

So I'm hypothesizing that it was caused by a lack of zero-point calibration after alignment, and that disconnecting the battery reset the sensors.

 

Joe I am a little concerned after reading through the article posted above by Crockettor that there will still be no way of knowing if the system is set correctly. It does appear that the by disconnecting the battery it will reset the zero point but you have know way of checking the rest of the vehicle stability control system is set correctly. This could possibly get you into more trouble if it took the wrong corrective action in a situation "having the wrong information fed into the ECU's" such as you came across in the snow.
I would treat the method outlined as a temporary measure after tracking without the correct equipment to do a complete reset.

The mini VCI with Techsream on Ebay at around $30 is a great investment for those wishing to do as much DIY work as they can on there Prius. It is capable of almost anything needed apart from security related work but will program extra fobs. This will savemore than it's cost the first time it is used.

John (Britprius)