ABS relay

Capturing oscilloscope pattern of ABS relay with two channel oscilloscope.

We used two pin probed to connect to power side of the relays.
ABS main relay number K38 and ABS motor relay number K100


Here is an oscilloscope pattern of ABS main relay and ABS motor relay.

On this graph we can see ABS ECU relay self check when its firs turned on (top graph on the photo).
Also we can see that ECU check ABS pump, it triggers it as power goes to 12 volts and them we can see osculation as the pump stops (bottom graph)


This first self checks required as the car which has got ABS system in it also have an ABS warning light, this is for the driver to inform of the conditions of ABS system. If light goes off in around 5 seconds after the car first time started, it means the system normal and in working conditions. When light stays on constantly this will mean system faulty and need attention and will not work until fixed.

We used plastic pipe to slow down Left rear wheel speed sensor and also captured and oscilloscope pattern of ABS motor. On the picture we can see that when brakes applied and ECU detects one of the wheels rotates slower then the others it turns on the ABS pump to ether decrease or increase braking force on that wheel.