The mechanic checked with the diagnostic scanner and confirmed that it was because the speedometer and odometer were not working.
He checked some other stuff which I didn't understand -- something to do with vehicle sensors.
He said he suspected the car computer and that he would need to read the manual to see if he can fix the computer but I may have to take it to a dealer for expensive repair or replacement of the computer.
Also, the mechanic mentioned that the car would not pass California Smog with a non-functional speedomoter/odomoter.
There's a sensor in the transmission that tells the instrument panel how fast the transmission is turning. Sometimes that sensor breaks.
It could also be a cabling issue somewhere.
Because without the odometer running, they can't query the computer to get accurate engine information. If they want to know how much gas you're using per mile, for instance, they need to know how many miles you have gone.
If it is the computer, you an expect $800-1100 just for the part.
I'm not sure where it is on this car, but they are usually either behind the glove box or in the pass. side kick panel. They are easy to replae; the plugs only go in one way. Expect to pay a lot to have a dealer do it.
if you go to
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they are anywhere from ~$150 up. It will not have the correct mileage. Also, make sure to get the correct one for your car.
It is unlikely that the car's engine control computer, referred to as an electronic control unit, or ECU, needs repair or replacement because they have a very low failure rate. A competent technician who is familiar with Toyotas knows that the engine ECU is the last thing to check, not the first thing to check. Even if the engine ECU did need repair, it would have to be sent out to an authorized repair facility for repair.
The reason that the car would not pass smog is that vehicles with the check engine light (actually called the malfunction indicator light, or MIL) illuminated automatically fail, and the reason that the MIL is on is because of a problem with the speed sensor circuit.
There is a speed sensor on the transmission that sends a signal to the speedometer control on the back of the instrument cluster, and diagnosis is pretty straightforward. The On-board Diagnostics Generation II (OBD II) scan tools used by professional technicians should have the ability to read the signal generated by the transmission speed sensor and therefore check the function of the speed sensor. Even if the technician's scan tool does not have this capability, the sensor can be checked with a volt meter at the sensor itself.
If the sensor is putting out the proper signal, then the next step would be to check the wiring between the speed sensor and the speedometer control by checking the signal at the wire harness at the speedometer control. If the signal is good, then the speedometer control is bad, and if the signal is bad, then the wiring between the sensor and speedometer control is bad. The most time consuming part of doing all these checks would be removing the instrument cluster to get at the speedometer control, about a half-hour total for all the checks.
If anyone did any work just before the speedometer started acting up or if you had any electrical work done on the car like installing an aftermarket remote starter or audio system, I'd check that work first to make sure that the speedometer circuit wasn't disturbed.
the engine computer gets the road speed from the speedometer, actually there's a cable or switch on the transmission that both the speedometer and engine computer use.
Sounds like the other guy was a parts swapper? Swap out this and that and hope it works. And of course they want to start with the most expensive item.
********** I think an unintended consequence of the OBD II standard and the widespread availability of OBD II scanners is that people with just enough knowledge to identify and find a part in a car can swap parts.
The possibility that the engine ECU is causing the OP's speedometer problems is not zero, but in 15 years of working for the company that made the OP's car and working with over 100 dealers, I have never heard of an engine ECU causing the symptoms that the OP is describing.
I think I know what is causing the problem, but since a proper, professional diagnosis only takes about 5 additional minutes, I'd check inn the sequence I mentioned.
Been there, done that when the replacement part is cheap and I don't feel like crawling under the car more than once, like in the middle of January in Chicago
I almost wish that the parts swapper had done that to my car. Had a 91 Camry a few years back that started running rough and would sometimes cut off. I put in plugs, coil and wires. No help. The Autozone help page mentioned a mass air flow sensor (think that was it) but it cost over $ 500. Thought I would take it to a dealer to find out. After 3 weeks of swapping parts out, they finally decided on that sensor and it fixed the problem. I wound up with about 2 or 3 othe sensors for about $ 100 each, a new set of wires as I had not used Toyota wires and a few other things. By the time they finished with it, I had about $ 1400 in the repair. I would not have minded the cost of the $ 500 sensor and labor to change it, but it really ticked me off they replaced other things and took 3 weeks to repair it.
the dealer should have put the car on a scope to check the ignition system. Aftermarket ignition can cause those symptoms that the parts can be checked with a scope. The MAF sensor probably only needed cleaning.
Cleaning it sure would have saved me a bunch. That dealership is not known for very good mechanics, I found out later.
I doubt they even know how to use a scope on the engine.
A co-worker took a car there for running rough. They changed the spark plugs among other things. Car ran ok for a week and then acted up again. The co-worker decided to look at the plugs and found they had only replaced
7 of the 8 plugs. It was not replaced as it was very hard to get to. Had to be an origional plug as it was a differant brand than the other 7.
This is a Ford/Toyota dealership and it was a Ford with the 8 plugs.
The hot wire can get dirty, and the dirt can act like an insulator and prevent the air flowing past the sensor from cooling the wire properly. The sensor is not supposed to be serviceable, but a shot of brake cleaner sometimes does the trick.
In the case of the mechanical sensors, you can usually get into the potentiometer element and give it a shot of a pot cleaner like Cailube, and that will fix a lot of these problems for a while. While you're at it make sure the vanes turn freely and put a drop of light machine oil on each of the bearing points.
Inspect the element, though. If it's visibly worn, you may just have to replace it.
Oops, my bad. When I responded to Ralph Mowery's post that mentioned a MAF sensor, I assumed the car had one without thinking about the model year.
To Ralph, Toyota referred to the potentiometer type sensor on that vintage Camry as an "air flow meter." Air flow meters were pretty reliable so I could see why it was low on the list of suspects but they are easy to check with a meter.
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