Operation CHARM: Car repair manuals for everyone.
Manuals through 2025 now available!

Our trusted friends have launched a new website named LEMON, which has newer manuals. It also contains all the CHARM manuals.

LEMON is the spiritual successor to CHARM, I recommend you try it!

Link: lemon-manuals.la or lemon-manuals.org.ua

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Wheel Speed







Wheel Speed
The Antilock Brake System (ABS) Electronic Control Unit (ECU) informs the Automatic Slip Regulation (ASR) ECU of the wheel speed.
- This is to allow the ASR to reduce the throttle opening in the event of wheelspin.

The signal enters the ECU as an incoming signal and is converted in the ABS ECU to a Pulse Width Modulation (PWM) signal.

Pins 9, 10, 11 and 12 are connected on cars with ASR.
Pin 9: right rear
Pin 10: left front
Pin 11: right front
Pin 12: left rear

The signal is an AC voltage, 0.15-0.70 V AC.