NO: | SYSTEM NAME | LOCATION(PIN No: |
1 | Ignition switch (protection relay) | K39 |
2 | ABS motor relay (pump) | K100 |
3 | Hydraulic modulator (system relay) | K38 |
4 | ECU Input | 26A (pin #1) |
5 | 2(J) Relay Control | 1B (pin #86) |
6 | (R/Y) from ABS relay | 1B/2A (pin13) |
7 | (2) Hydraulic Control Unit | 4A (pin 11) |
Multi-meter/OscilloscopeTEST reading.
Before capturing the relation between two pattern using an oscilloscope, we manage to back-probe relays and measure the voltage as it change in different state. When the ABS switches off The voltage on relay control circuit from the oscilloscope 0.45 volts at 86 where 0v at 30. This wiring diagram illustrates that the 86 and 85 is the control circuit and 30 and 87 is the switch circuit. According to the diagram 30 is the negative terminal of the switch and 87 is the positive, therefore it is the reverse in this course. Now without the power as we measure Pin #86 the switch is not activated which gives the reading of 0V at pin 30. As I turn on the power the voltage at pin 86 reads 12v as well as pin number 30 so this tells us the relay is working.
Example of Pump Relay Vs Relay (Waveform)
Relay Waveform: The next test excise shows both the control circuit change when the relay turns ON. Using the oscilloscope with two channels showing the relation of the two pattern.
Channel 1 - PUMP. Channel 2 - Relay
A - Key is switch ON E - ECU earth with voltage supply
B - The Key is ON (On Time) F - ABS Pump start spike
C - ECU is now earth triggering G - This shows the relay oscillation.
D - Relay is OFF (safety)
H - Relay (OFF) The pump stop working, and the inertia keep the pump running for a short time, this creates EMF. C and H - this indicate SELF TESTING. the relay turns on and the voltage supply to the Pump and so the pump is operate. (power to Pump)
ABS Pump Relay waveform:
Solenoid relay:
A - Key is switch ON.
B - Relay is switch ON and solenoid is working (Self Test)
C - Relay switch OFF
D - Key is OFF
ABS Self Test
Self-test is when ECU checks if ABS is powers up all the circuit throughout several functions like Hydraulic control unit with ECU, Inputs and Outputs. The ABS light stays on till the motors starts, In this case the light remain on until the safety relay switches the ABS motor relay. This happen when the light goes off and the motor starts as ABS relay turns on. This demonstration is showing in the circuit below.
Create a fault
To create a fault we applied pressure to the brakes by pressing the pedal and with more pressure applied to the fault wheel, as that wheel is braking harder than the other, this actuates the solenoids to relieve pressure on one wheel that has too much pressure, this allow the wheel to catch up speed with the other.
Catch an oscilloscope pattern when an ABS solenoid has actuated. What is the pin and name of the solenoid? Pin 30 ABS pump motor relay
How did you do it?
We back probed pin 30 on the ABS pump motor relay using a piece of wire, which is connected to the relay and back to the oscilloscope.
A - Key is ON. B - Key is OFF. C - Pressure is now apply to the wheel
The ABS works when pressure increase in the brake system, the solenoids will open and closed the valves to hold and reduce pressure. As this happen the advantage of the driver is can still take some control to the steering.
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