2002 Prius 155281miles: odometer not work, fuel gauge unstable, check engine light on

With all of the work around bearings, struts, brakes, etc., I think it might have been easy to disconnect one or more of the wheel speed sensors (there's one at each wheel) and either not remember to reconnect them all, or perhaps have a dirty or insecure connection at one or more of them.

I'd start with a careful visual reinspection of all four speed sensors and the connections to them. If that doesn't lead to the problem directly, I'd suggest following the speed sensor diagnosis procedures in the service manual volume 1. If you don't have the manual yet (either on paper from helminc.com or online at techinfo.toyota.com), for the amount of work you are doing on the car it will probably save you a lot of trouble.

Hope this helps,
-Chap

 

Comments inserted:

* * * quoted material * * *
I have a 2002 Prius, and I have been struggling trying to get it fix.

How long have you owned this car? Where did you get it?

But it's either one thing to the next without completely knowing what's what.

It is important to have your own copy of the two volume, Maintenance Manual, or subscribe to the TIS service.

Recently, the right front bearing and the left rear bearing, both front struts/shocks, right balljoint, and two front brakes were replaced.


Why?

Before these replacements, I had a P1436 code for the valve which was lube but nothing happened.

It can also happen if the vacuum mechanism that drives the valve is broken.

Then after replacing the front struts/shocks, turn the car on for a test drive, brake light and check engine light came on, speed odometer it not working. I used the OBII scanner from autozone and got P0500 said: vehicle speed sensor A malfunction.

You need a Prius-aware scanner. There are Prius specific codes an Autozone scanner can not read.


So far I unplug the 12v battery from the back for about an hour then plug it in and charge it up...nothing

What are the voltages? The reason is the battery itself could be bad.

the problem there, gas gauge up and down as I drive, speedometer still not working.

The gas gauge problem is associated with the 'level sensor' (search this forum) . Speedometer, remember I mentioned the Prius specific codes.

Please help!!! Thanks

Ohh I forgot to mention that we went to the dealership and they gave us a printout of the transmission to see which sensor is the A malfunction, so we bought a sensor and try couple days again but the problem still exit so we took the sensor back to the dealership. Any suggestions?

* * * end quoted material * * *

If this is a salvage car from an auto auction, the first thing to realize is a Prius is not an ordinary car. The driver is operating the control computers and a Prius-aware scanner is how you get the errors they are reporting.

This Prius has seven control computers of which three are critical to its operation: engine, battery, and hybrid vehicle. The others handle body, brakes, steering, air bags, e.t.c. Without the maintenance manuals and a Prius-aware scanner, this car will be frustrating to the point of impossible to repair. Thinking it is "A" when actually it is "B", a working part can be swapped out . . . not fixing the root cause. Worse, the root cause, likely known to the control computers, is ignored.

Bob Wilson

 

Comments inserted:

* * * quoted material * * *
Thank you for your help. Im the one that fixed the bearings and strut towers posting this reply.

Ahhh, this is a customer's car? Sometimes we get folks who buy broken cars from salvage thinking they can swap parts and voila, resell the car. They often learn more than expected.

I've been saying it needs to be scanned as well from the dealer or recalibrate the ecu. If im not mistaken the ecu runs both gas and speedo so seeing a problem start in both leads me to think its something in the ecu.

There are multiple ECUs and the schematics really need to be studied to trace and check the signals. Even after repairing one set of problems, others can be revealed. Having a Prius-aware scanner is the way to go.

I just cant understand why the speedo dropped out when i was nowhere near the sensors in transmission. shes missing an abs sensor ring on passenger side but wasnt there before. The only thing i can think of is the car was shifted into nuetral with one tire off the ground and when it was shifted i watched the wheel move forward and back like it was checking itself. You know if one wheel moves like that if it would error in the ecu and is there anything else i can check before taking it in .i can only think if that caused the problem jacking both wheels up and shifting it through?

That might work on other cars but the Prius is more complex. The transmission has two, very strong motors and trying to diagnose a problem by watching the wheel movement is not likely to work.

Shes ordering manual but carneeds inspection soon. Anyone besides the dealee have a scanner that would work?

The XHorse miniVCI works if you have a Windows XP, PC with USB interface. Another choice is AutoEnginuity, at $500, more expensive but it is supported and in production. A Scangauge can be used but requires adding XGAUGE programming, not difficult but time consuming.

* * * end quoted material * * *

Bob Wilson

 

I'm not convinced the speedometer even relies on a sensor the tranny. With one at each wheel required for ABS anyway, nothing more would be needed. (No mistake, the HV ECU always knows how fast MG2 is turning, which could be translated to road speed, but I'm pretty sure the speedometer relies on the wheel sensors.)

By the way, reading the codes from the brake ECU should give you an idea which wheel sensor(s) to check. C0200 for right front, C0205 for left front, C0210 right rear, C0215 left rear. Those are blink codes 31, 32, 33, 34 respectively if you don't have a Priusy scanner and don't mind counting light blinks.

-Chap

 

You could be right about 4 sensors in the tranny - if you're counting the MG1 and MG2 temperature sensors and the MG1 and MG2 resolvers, but I doubt any of those is what you're looking for. As I mentioned, the MG2 resolver signal could be used to derive road speed, but I don't think that's how the speedo does it.

I understand that you don't know any of us on this forum so it can be hard to judge whether we're giving you sound information or not. At this point probably your best bet is to sign on at techinfo.toyota.com for instant access to the manuals and follow the diagnostic steps in volume 1. It will tell you how to get brake system diagnostic codes blinked out at you without needing a special scanner. I recommend following up any problem for which a code is shown. For example if you already know of a problem with one wheel speed sensor, that is probably worth following up.

Good luck,
-Chap

 

I'm not sure I fully understand your question, but yes, there is a sensor at each wheel and they all generate signals (presumably at the same rate in straight-ahead driving with matched tires on dry pavement). There is something interesting I remember stumbling upon in the manual where one of the ECUs (or was it the combo meter itself) uses the raw wheel sensor inputs and generates its own conditioned pulse train that's then shared with other devices. It sounds like you now have access to the manuals so you can probably find that bit.

I'm still confident that if you pull diagnostic codes and correct whatever speed sensor issues they indicate, you'll be back on the road. Have you got any codes yet?

-Chap