What is the logic of warning codes?

[lekjart]

I recently had the engine check, VSC TRC and VSC OFF light up suddenly on my 2003 lc100. Only thing recently changed was renewal of exhaust pipes, but that was more than a week prior. Anyway, got the codes scanned and the result were c0215 and p0156, which correspond to rear wheel speed sensor and O2 sensor, bank #2, sensor#2.

I know there can be multiple reasons for these and I have seen a few threads about it here, but...

Now the funny thing is that the light persist for days while I do only city driving, but if I drive longer distances like for more than an hour the lights will typically disappear next time I turn on the engine.

I have two questions:

1. Why would these two unrelated codes turn on simultaneously? How can they be linked?

2. Why would driving longer hauls make them go away, again simultaneously?

 

[LandCruisinMy93]

Could potentially be 2 separate issues. I used to get the vsc, trc, cel combo on my 2003 sequoia and it too would go off after hitting the highway for a bit. The Sequoia was fully maintained by me and kept up to date on everything. I even replaced Heater core hoses when doing the waterpump etc... every 105k. Even with brand new O2 sensors from Toyota the problem persisted. It seemed only to happen when it was cold out. Literally only ever occurred during winter months.

Honestly It is likely a programing issue or the ecu is not seeing the numbers it wants to see from the engines sensors. The problem with fuel injection is that it relies on an array of sensors to adjust itself and if one sensor is a little out of whack it can throw codes not directly related to it. Like an O2 sensor code from an ambient air temp sensor or water temp sensor. I've seen cars running poorly and getting bad fuel economy from having a broken Sideview mirror...because the ambient temp sensor was in the mirror housing...dumb.

If it isn't a blinking CEL just drive and check the code later. I ended up just carrying my OBD2 scanner during winter and deleting the codes.

 

[LandCruisinMy93]

VSC/TRC would be from the wheel speed sensor. If there is a discrepancy between projected wheel speed and actual wheel speed the traction control/ vehicle skid control will turn off. If the engine or accelerator pedal aren't performing properly it shuts off also.

 

[Brandon Ryder]

Was one a pending code? A pending code won't trigger a check engine light but its there because the problem is intermittent.
Another issue pops up that does trip the light, so you check, and finally see the pending code.

 

[lekjart]

VSC/TRC would be from the wheel speed sensor. If there is a discrepancy between projected wheel speed and actual wheel speed the traction control/ vehicle skid control will turn off. If the engine or accelerator pedal aren't performing properly it shuts off also.

So are you saying that the 02 sensor problem might trigger and engine warning that would then trigger the VSC/TRC? In that case, why would it specifically trigger the wheel speed sensor code?

 

[studawg]

Only thing recently changed was renewal of exhaust pipes, but that was more than a week prior.

What exactly does this mean? Which pipes? Were the O2 sensors touched? Were they replaced? Are they OEM?

 

[lekjart]

No, I don't believe the sensors were replaced, but they probably might have been somewhat nudged in the process. The pipes switched were after the catalytic converter.

 

[GTV]

So are you saying that the 02 sensor problem might trigger and engine warning that would then trigger the VSC/TRC?

In my experience if you get one you get them all. Something as mundane as an O2 sensor will light up all three. It's how Toyota does it.

 

[LandCruisinMy93]

@lekjart I am saying that your O2 sensor code may not necessarily be the O2 sensor and that other sensors giving false or inaccurate signals can throw off the ecu.

In my original post I mentioned it may be 2 separate issues. You may have a bad wheel speed sensor which can shut off the VSC/TRC and also if your engine isn't running properly it can cause the same thing to happen.

What I was eluding to is that I had the same issue on my 2003 sequoia with the same drivetrain and eventhough it had new Toyota O2 sensors it would still throw the bank 2 sensor 2 during winter months. It may be other sensors sending signals out of the operating parameters and your ECU adjusts fuel to meet those out of spec parameters and it is the O2 sensor catching the error. The only way to really know what is going on is to look at the live data and check all of the sensor outputs against the factory specs. If all sensors are outputting properly you may have other issues.