What to do with my car? please help

liliananz, Dec 30, 9:40am
i have toyota vitz 2001. the engine light on sometimes while i am driving. I went to have it check. the problem code is po500. says speed sensor malfunction. The code was cleared. Then the light went on again while i was driving. I went to back to get further check with scope (is it right!)
The computer analysis says there is nothing wrong with the speed sensor. The car went on rode test. it was noticed that when the engine light on, the diagram states that speed sensor made some noise regularly.
well. i had two suggestions by the mechanic. the one is doing transmission flush service to see if clean will help. the other is replaced the speed sensor. However, there will be no guarantee that problem will be solved.
which solution shall i do! i want to choose the most economic way.
I know nothing about the car. any advice will be helpful
regards

00quattro00, Dec 30, 10:05am
Well its worth doing the trans service as it will need to be done anyway, and a new sensor should not cost much either

franc123, Dec 30, 10:05am
Going to a Toyota agent for a proper analysis and testing by a tech that knows what they are doing and has access to the correct info would be a good start, it may well be a known problem. Fault codes are only generated when the particular ECU involved has detected a signal that it doesn't understand, or is outside what it expects to see, this can be a sensor or circuit fault or even another operating condition causing odd behaviour from the sensor. They don't log for no reason, deleting the code isn't going to solve anything if there is an underlying issue. Has there been any odd readings from the speedo or has the trans been shifting at the wrong time or anything like that! The idea that a trans flush might solve an electrical issue is funny to say the least.

farnortherner, Dec 30, 10:23am
Well try this link
http://www.obd-codes.com/p0500
Symptoms of a P0500 DTC may include:
loss of anti-lock brakes
the "anti-lock" or "brake" warning lamps on the dash may be lit
the speedometer or odometer may not work properly (or at all)
your vehicle's RPM limiter may be decreased
the shifting of an automatic transmission may become erratic
other symptoms may also be present

farnortherner, Dec 30, 10:24am
Causes
also on link above:
A code P0500 may mean that one or more of the following has happened:
The Vehicle Speed Sensor (VSS) is not reading (functioning) properly
There is a broken/frayed wire leading to the vehicle speed sensor
The vehicle's PCM is not correctly configured for the actual tire size on the vehicle

farnortherner, Dec 30, 10:25am
also on that link
Possible Solutions
The simplest thing to do is to reset the code and see if it comes back.

Next, check all wiring and connectors that lead to the speed sensor. The location of the sensor depends on your vehicle. The sensor could be on the rear axle, transmission, or perhaps the wheel hub (brake) assembly.

If the wiring and connectors are OK, then check the voltage at the speed sensor. Again, the exact procedure wil depend on your make and model of vehicle.

If everything looks OK, replace the sensor.

farnortherner, Dec 30, 10:26am
Hope that helps, Im no expert at all but found that on the net

liliananz, Dec 31, 1:06am
Thank all of your advice. I just have no idea about the car. I wrote this thread because i don't want to be tricked by the mechanic to waste some unnecessary money at the moment. It seems like that I will not do the transmission flush service now. and I will ask a few mechanics to see what they say. anyone in the north shore can recommend some decent ones!
thanks and happy new year!

intrade, Dec 31, 1:09am
go to the main toyota agent they are on north sore i think.thats all i can say if you go round asking loads of mechanics then they either rip you off or they think you want everything for free and tell you to bugger off.

meathead_timaru, Dec 31, 1:13am
Keep going to different mechanics, wasting their time, until you get the answer you want.

firemansgirl, Dec 31, 1:19am
Well you're just a source of helpful information - NOT!

meathead_timaru, Dec 31, 1:22am
They're not looking for information. They're looking for someone to tell them what they want to hear.

liliananz, Dec 31, 2:46am
Gee guys~~don't argue, it is new year eve.
thank you for all of your kindness.
i am just naive about the cars and unlucky, i don't have many male or female friends who know the cars.
and at least, i wont do the transmission flush service to try to fix my problem after i read your answers. see, that is useful for me!
i may go ask for toyota agent, i asked them once, they sounds expensive. but this time i will ask them again.
once again, any information i will be appreciated.
happy new year!
Regards
Lillian

chevcamaro, Dec 31, 3:12am
i second that, i think

theram1, Dec 31, 3:12am
beats "santa did it".

kazbanz, Dec 31, 3:35am
ACTUALLY--he mayhave been blunt about it but he is 100% correct. The op was given the information they needed and solid advice to boot. Their reaction was to ignore that advice.
The hourly rate at Toyota will certainly be more than elsewhere but the car will be fixed efficiently which ultimately often means it costs less

llortmt, Dec 31, 3:40am
The speed sensor is on the top of the transmission (two wire held with one bolt), basically it sends small (4.5-5.5 volt) electrical pluses to the ECM (the cars computer). The ECM determines the vehicle speed based on the frequency of these pulse signals (sent via instrument cluster)
Clearing the code WILL put the light out at first as it has a 2 trip detection logic unless you FIXED the fault it wont help.
Personally I'd like to look a live data and see it faulting (whats the speedo needle doing!), plus test the sensor not just for a pulse but resistance (should be 560-680 ohms) but if I was to guess (an educated guess) I'd be replacing the sensor itself.
Having said that I'm not guaranteeing its not a harness (wiring) problem,ABS ECU fault, instrument cluster (yes really but unlikely) or even an ECM fault.
p.s. I cant see how a trans flush is going to help this fault, I be interested in their logic.

liliananz, Dec 31, 3:44am
thank you so much! thank you for your time to reply me! it is helpful!