What yaw is, and why you'd log it
Picture a line running straight down through the roof of the car. Yaw is rotation around that line. Turning into a corner creates some, and a car that's oversteering or spinning creates a lot more than the steering input asked for. A yaw rate sensor measures that rotation and outputs it as a voltage.
On a Haltech Elite, the yaw input is mainly a monitoring and logging channel. Once it's set up, ESP can raise an alert or diagnostic code when the reading goes beyond the limits you've set. For road race and drift cars, logging yaw next to steering angle, wheel speeds and throttle is one of the clearest ways to see what the chassis was doing through a corner.
Many modern cars already have a yaw sensor for their stability control system. Some aftermarket builds reuse the factory part, while others fit a standalone sensor. Either way, the ECU just needs a clean analog signal and a matching calibration.
Choosing an input
On the Wiring tab, assign the sensor under Yaw Input. Use an analog-capable input:
- AVI (Analogue Voltage Input): the recommended option. Its optional pull-up is 1k to 5V.
- SPI (Synchronised Pulsed Input): works if you're out of AVIs. Set Sensor Type to Hall Effect so the SPI reads it as an analog signal. The pull-up on an SPI is a weaker 10k to 5V.
Pull-up: on or off?
A yaw sensor is an active sensor with its own supply, so the pull-up should be off. Pull-ups are meant for passive two-wire sensors such as coolant or air temperature sensors, which need the ECU to provide a reference voltage. With a powered sensor, an enabled pull-up fights the sensor's own output and skews the reading.
The same applies if you're tapping into a factory yaw sensor that the car's stability control module still reads. That module already biases the circuit the way the sensor expects, so leave the Haltech pull-up disabled.
Tapping a signal wire is fine, but never add a second 5V supply or a second ground reference to a sensor another module is already powering. Just read the signal, and ideally share the sensor ground with the ECU's signal ground.
Calibration
The Calibration tab turns volts into a yaw rate. ESP includes a set of preloaded calibrations, opened with the yellow Open icon at the top left. If your sensor isn't listed, you'll need its data sheet. Enter the voltage points and the yaw rate they represent, then save it as a custom file with the blue Disk icon beside the Open icon.
Before you trust the calibration, sanity-check it in the car. Parked and still, the yaw reading should sit at or very close to zero. Drive a slow, steady circle one way, then the other, and the reading should swing in opposite directions by similar amounts. If it reads backward, the calibration's sign is reversed or the sensor is mounted the wrong way around.
Diagnostics
These two settings watch for wiring faults. Both ship disabled.
| Setting | Code | What it detects | Our advice |
|---|---|---|---|
| Raw Min | C1032 | Signal voltage below your set value | Enable, and set just under the lowest voltage the sensor outputs in use. Catches an open circuit or short to ground |
| Raw Max | C1033 | Signal voltage above your set value | Enable, and set just over the highest real output. Catches a short to supply |
If you're running engine protection, each fault can be given a DTC severity so the ECU reacts the way you choose. For a logging-only sensor we usually leave the severity low, since a yaw fault isn't an engine safety issue. The full code list is in our DTC index.
Mounting tips
- Mount the sensor solidly to the chassis, flat and level, as close to the car's center of rotation as practical.
- Line it up with the car's centerline. A sensor mounted at an angle mixes other motion into the reading.
- Keep it away from heat and heavy vibration sources, and use shielded cable on long runs.
Troubleshooting
| Symptom | Usually |
|---|---|
| Reading isn't zero when parked | Wrong calibration, sensor not level, or pull-up enabled |
| Left and right turns read the same direction | Calibration sign reversed or sensor mounted backward |
| C1032 or C1033 at key on | Unplugged connector, missing sensor supply, or Raw limits set too tight |
| Noisy trace in logs | Loose mounting, vibration, or a poor ground |
Setting up a chassis data package around an Elite? Talk to us and we'll help you choose the channels worth logging.
