Warning Lights: Simultaneous Illumination–Check Engine, VSC Off, and Traction Warning Lamps (Toyota/Lexus)

What it Does

On Toyota (and thus Lexus) products, it’s common to see these lamps: [check engine, VSC Off, and Traction Warning (vehicle with squiggly tire track lines) ] all come on at the same time.

Why This Matters

What has likely happened is that the check engine light illuminated for an engine management problem, and then stability control systems are either partially or fully disabled (not damaged!) because the vehicle has detected an engine management problem.

Possible Problems and Concerns

More scary than it needs to be:

It can be intimidating or concerning to have multiple warning lamps illuminate together. However, if all three lamps illuminate together, the root cause is most likely an engine management concern. Resolution of this concern will likely resolve all 3 warnings at the same time.

Engine Management Concern:

These can run the gamut from minor to severe. The check engine warning itself is no indicator of severity. It will turn on for engine misfires (severe concern level) all the way to a very small evaporative emissions system leak. (very minor level of severity, at least for engine performance and health.)

It’s healthy to focus mainly on the check engine lamp and remember that it can illuminate for concerns that vary both in repair cost and priority level. In other words, don’t assume those 3 lamps are “no big deal,” but don’t assume either that the vehicle has a severe problem and it’s going to be really expensive.

Please remember this too: People tend to get nervous about check engine lights, but sometimes they come on with no perceptible loss of performance or reliability. Part of what these warnings are used for is when the vehicle detects an emissions system problem or a problem that allow the engine to still run strong but not run as clean. (This would also affect emissions levels.)

Thus, it’s more accurate to call the “check engine” or “service engine” warning an engine-related fault warning, and then remember that faults can vary from severe to quite minor. Furthermore, engine-related includes fuel system and emission components that exist outside of the engine but affect it! Paying attention to how the car feels, sounds, and is acting can be an early indicator of whether the problem is severe or not. Proactive scanning of codes is commonly a good idea and further illuminates severity (or lack of.)

Why do these lamps act like this?

Stability control involves both removal and application of power. For example, some vehicles can limit power to one skidding wheel and send power to another wheel to help mantain vehicle control. In many other cases, the vehicle may assume consistent power delivery to both drive wheels even if it’s not designed to vary power delivery to individual wheels.

So if we look in detail enough at how inconsistent power delivery could affect tire traction, and how engine management problems may (or may not) affect power delivery, this raises questions of liability and risk. Most manufacturers are willing to turn the check engine warning on and leave stability system warnings off. It appears that Toyota chose to take a more conservative or cautious route.