P0500 OBD-II error/freakout - tire size related (mismatched sizes)?

[Mark]

I'm taking the car on a ~120 km round trip today with the wheel/tire combo from Mirage #2 installed (which caused zero ECM freakouts, and which appeared to be OK last night in a brief test drive). If it's uneventful, I'll swap the smaller rear tires back on when I get home and see if that triggers it again. That's where I'm putting my money.

That should be a good test of the different tire size combinations. Prior to ABS & traction/stability control being added to pretty every car these days, all this probably wouldn't have been a problem in the past.

What you are doing would be a big no-no on an AWD vehicle like my Forester. Running different size tire front & back wouldn't create drivetrain issues on a FWD car, but it may wreak havoc with sensors.

If you don't have problems today, but they reappear when you go back to the 165/65r14 tires you will most likely have your answer. I would suspect large difference in tire size is the problem, but I am just guessing, too.

[Fummins]

Funny: I've gotten the ABS/Traction control freakout when I was idling the car in gear on jack stands to "machine" rusty rotors. But that problem clears itself the next time you drive the car. Like within half a block.

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I've had a ScanGauge-II plugged into this car without issue, as I did in Mirage #1 and #2. That said, the first thing I did when I saw the dash light up was yank it out after clearing the code. And then problem returned multiple times with it disconnected.

That said, it was really hot yesterday, and the SG was sitting on the dash in direct sun. That made me wonder if it got hot enough to somehow malfunction and piss off OBD-II. But I kinda doubt it. The SG looked to be working normally.

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I'm taking the car on a ~120 km round trip today with the wheel/tire combo from Mirage #2 installed (which caused zero ECM freakouts, and which appeared to be OK last night in a brief test drive). If it's uneventful, I'll swap the smaller rear tires back on when I get home and see if that triggers it again. If it does, then I have the definitive answer.

Gotcha. I'll go with mismatched tires is causing your problems. For now.

Weird that mismatching tires would kill the power steering like that.

But a burnt out brake light bulb can make these things drive like pooh and throw abs/trac lights so anything is possible.

[Mark]

Gotcha. I'll go with mismatched tires is causing your problems. For now.

Weird that mismatching tires would kill the power steering like that.

But a burnt out brake light bulb can make these things drive like pooh and throw abs/trac lights so anything is possible.

Today's car are goofy when it comes to wiring & electronics. My Forester tends to sit more now. Mice ate the wiring near the gas tank some time ago. That caused the dash to lit up (traction control, ABS, & few others came on). Cruise control was also disabled. The problem went way beyond the gas tank reading empty (actually the gauge was just dead).

Once the wires were spliced back together, everything was good again!

[MetroMPG]

But a burnt out brake light bulb can make these things drive like pooh and throw abs/trac lights .

OOh, I forgot about that. I'm gonna check lights that before I go.

And also make sure someone didn't secretly install LED bulbs when I wasn't looking.

[MetroMPG]

That should be a good test of the different tire size combinations. Prior to ABS & traction/stability control being added to pretty every car these days, all this probably wouldn't have been a problem in the past.

True. I do the reverse on my craptastic Miata (bigger wheels on the back, for the same reason). A 31 year-old 2WD car couldn't care less what's bolted to its hubs.

[Eggman]

How’s the wiring for the wheel speed sensors?

[7milesout]

What you guys fail to realize is that our expert gobment beauracraps that mandate these things actually know better than us, and know better than auto engineers. What you goons fail to realize is when all these lights come on, that your vehicle is actually skidding out of control, and death is imminent. Why would these warning come on otherwise?

So, just drive a lot slower, and maybe you'll regain control and quit skidding all over the road.

[Mark]

So, just drive a lot slower, and maybe you'll regain control and quit skidding all over the road.

Yes do that!

Eliminate touch screens on dashes of vehicles, & I believe roads would become a bit safer, too!

[MetroMPG]

So far so good: I've put a couple of hundred km on the car with the tire size setup from Mirage #2, and no Christmas tree dashboard of death!

Also checked the brake lights (all good).

Eggman: I'm guessing this isn't a wiring problem mainly due to it occurring immediately after the wheel change, and going away after the 2nd wheel change.

Next step: stick the original tire size on the rear to confirm that here comes Santa Claus, here comes Santa Claus...

[Eggman]

So far so good: I've put a couple of hundred km on the car with the tire size setup from Mirage #2, and no Christmas tree dashboard of death!

Also checked the brake lights (all good).

Everyone likes an easy fix.

Eggman: I'm guessing this isn't a wiring problem mainly due to it occurring immediately after the wheel change, and going away after the 2nd wheel change.

That's good because there's been reports of rear axle wiring problems for the speed sensors.