CARspec recently had the opportunity to address a concern another local shop couldn’t resolve – occasionaly while accelerating on dry pavement, with our without turning the steering wheel, the vehicle stability control (VSC) system would activate. The VSC light would blink, the traction control would take over the engine’s output and the ABS would sometimes engage. The owner noted the ABS locked the brakes up once during the malfunction. There were no stored trouble codes, the problems only acted out intermittently and previous mechanics had declined to try and tackle the issue any farther.
The stability control system uses a suite of deceleration, yaw rate, wheel speed, acceleration, braking, and steering angle sensors to determine the driver’s intent vs. how the car is behaving. If you are attempting to turn slightly to the left and the yaw rate sensor suddenly detects more leftward movement (transitioning from a right bias to a neutral or leftward force), it indicates the vehicle is sliding. The VSC will use the ABS to try and correct the angle of the vehicle by applying individual brake force at the appropriate corner. When it works it is an amazing safety feature.
In this vehicle the root cause was the steering angle sensor intermittently showing the wrong steering angle. The VSC thought the driver had suddenly changed the steering while the rest of the VSC system noted nothing was happening – ie. the steering had changed direction but the car hadn’t. At this point the VSC stepped in and went nuts trying to work with incorrect data.
The solution was a new steering angle sensor. The part has since been updated to correct this known issue. Here’s the old, failing unit:
Sienna Steering Angle Sensor
The sensor was replaced and the vehicle returned to service, now with a VSC that wasn’t losing its mind.
CARspec is Minneapolis’s premier independent Toyota, Lexus and Scion repair specialist and the above reflects our expertise – often we’re tasked with fixing the issues other independent shops can’t, like this transfer repair, timing complex Toyota engines or this suspension conversion. If you are in need of diagnostics or repair on your Toyota, Lexus or Scion don’t hesitate to give us a call at (952)426-4798 to make an appointment today!
I have a 2005 Toyota Sienna where the vsc system activated and slowed our van down. When it first happened we thought that the van broke down because there was a beeping sound and it seemed like the brakes activated by itself. Kinda scared us because we were going around a turn at 35mph We then noticed that the system activated every time around the same turn and we prepared ourselves every time we went around that turn. We tried going at different speeds and 90% of the time it activated at the different speeds. I read up on what the vsc system does and now the vsc activated at a different location that scared us again because we were going 60mph. Tried searching for possible causes for the activation on the internet. I noticed that all of the activations are on left turns. Was wondering if a bad suspension would activate the vsc system? Maybe the van is tilting past an acceptable angle on the turns and the system senses that?