Odometer/Speedometer issues…Help!

[Tijuana Taxi]

I just bought a used 2011 Mazda3 s GT. It had 93,600 miles on it, as I witnessed with my own eyes on the test drive. I noticed that the speedometer was 9 mph off - it showed 62 when I was actually driving 71mph. I decided to buy it, and the used car dealer then showed me how the telescoping/tilt wheel worked. Once I got it home, I noticed that the odometer read 300 miles - that's it! Should I suspect a bad speed sensor, a loose connection near the instrument cluster, a bad fuse, or some other problem? Do you think the odometer and speedometer issues are related? Thanks.

 

[negusm]

Larger wheels will cause a change in readings.

Speedometer Calibration

Speedometer calibration made easy. Use our speedometer calibration calculator to compare how fast you are traveling and your speedometer reading.

tiresize.com

On the 300 miles...that is weird. Might be a bad cluster. A blown fuse won't allow any of it to work. More likely would be a bad connection or bad cluster.

 

[concept]

I would call the place from whom you bought the car and ask them to explain why the odometer reading is so low. Most cars are advertised with the odometer reading. 300 miles would be a red flag to me, so that may be why they didn't include it in their advertisement.

On the other hand, you could be looking at one of the tripmeters.
Regarding the speed being off: Are the tires OEM size?

 

[Tijuana Taxi]

Yes, the tires are OEM size. And even if they weren't, that wouldn't account for more than maybe 2 mph. And the used car lot advertised the correct mileage. I did find out the speedometer had been replaced just recently. And yeah, at first I thought I was looking at one of the trip meters. I had to look twice - or three times. I'm thinking I might have a short in the instrument cluster. I hear a faint relay noise (like a small fan motor running) all the time coming from near the cluster, even after shutting everything off, and even coming in in the morning when the car hasn't been running at all. It's not the radiator cooling fan, which would be much louder. This is very faint, but there.

 

[TheMAN]

you shouldn't have bought a car that's dodgy and raised red flags

 

[TheMAN]

Larger wheels will cause a change in readings.

Speedometer Calibration

Speedometer calibration made easy. Use our speedometer calibration calculator to compare how fast you are traveling and your speedometer reading.

tiresize.com

On the 300 miles...that is weird. Might be a bad cluster. A blown fuse won't allow any of it to work. More likely would be a bad connection or bad cluster.

on mazda3s, the speedometer is "married" to the car... you don't just plug it in... various things have to be set, including wheel size, which is responsible for the speedometer correctness

 

[concept]

Did you call the previous owner or car lot salesperson?

 

[Tijuana Taxi]

Did you call the previous owner or car lot salesperson?

I'm gonna stop by there on Tuesday and see if they have any further info.

you shouldn't have bought a car that's dodgy and raised red flags

Well, you're right. Overall, though, the car is in good shape and runs well. I probably was in too much of a hurry to find a car when my Tijuana Taxi got totaled by a deer on April 6th. A shame. I loved that car. It still runs great but it's too damaged to fix. I am selling it to a young mechanic. I finished with 321,200 miles.