On-Car Exercise(ABS CHECK)



On-Car Exercises

Assigned to identify the following components to the tutor:

1 wheel speed sensor

This is an inductive type sensor locate at the left front wheel of this vehicle as you can see is not much room to measure an air cap, anyway we manage to get to the air cap and is 0.82mm depth match the spec. 

2 ABS Control unit. 3.ABS modulator. 4.ABS pump

Here we found a modulator, pump and ABS control unit which attach to one unit and located near close to the master cylinder for this vehicle.  

5. barking brake switch. 9. Foot brake switch

Number (5) shows for most vehicle normally located between the front seat to the driver, the brake switch is attach to the handle under the frame. Some automatic transmission used the foot pedal instead of hand to apply this brake. Now number (9) indicate the foot brake switch for this vehicle.

6. Brake master cylinder. 7 Brake fluid level switch. 10 Brake booster

This is a tendem master cylinder and is bolt to the brake booster which is normally locate under the dash-board next to the driver's lower side connect to the brake pedal. 'The brake booster of this vehicle is shows on the white mark (number 10) It helps the driver to compress and release pressure. 

8. RPM Sensor

The sensor mounted to the engine crank attach to the pully, position to the ring teeth of the crankshaft. most vehicle these days have their RPM sensor operate inside the ignition distributor (inductive type) giving out analogue signals.(AC)

 

11 ABS control unit fuse

This is the Fusible link where ABS modulator relay, pump relay, fuses and other connector are located, inside a small fuse box. the box cover give the instruction so we can locate them. 

Front / Rear Wheel Speed Sensor Located.

Front Right - 0.82mm      Front Left - 0.335mm

This vehicle fitted with ABS system, we also identify and located each component. The wheel sensor used is inductive type (magnetic/pulse generator) reads analogue signals.

Rear Wheel Speed Sensor

In this vehicle both rear are drum brakes, and with the wheels speed sensor mounted inside the rear drums we could not reach to the point where we can measure the air cap.

2: sensor 1: ring teeth

Analogue test using an oscilloscope

Voltage 0.5v/div. Time 5ms/div 

For this analogue signal we need 15kM/H or 20KM?H for the inductive type sensor

Frequency: 115Hz at 15KM/H

If we can compare the frequency scale on multi-meter by turn the wheel toward speed of other result than it could be a closed result depend on the turning wheel. The multi-meter shows AC waveform change both frequency and voltage to increase and decrease rapidly. Low speed give a low voltage signal indicates slow in frequency, higher speed gives a higher voltage signal also indicate higher frequency.

Using a Scan Tool

 ABS live data at the engine's high speed

This recording data shows that all solenoids are in off position, battery voltage at14.64v and both (LF/RF) sensor are on 71 KPH with the engine at idle.

Current Data A

HYDRAULIC PUMP MOTOR	OFF
LF ABS IN VALV	OFF
LF ABS OUT VALV	OFF
LF WHEEL SPD SENS	71 KPH
LR ABS IN VALV	OFF
LR ABS OUT VALV	OFF
LR WHEEL SPD SENS	O KPH
RF ABS IN VALV	OFF
RF ABS OUT VALV	OFF
RF WHEEL SPD SENS	71 KPH

Current Data B 

Vehicle's hard braking (stop)

Current Data A

ABS VALV CTRL RELAY	ON
ABS WARN LAMP STATUS	ON
BAT POSITIVE VOLT	13.02
BRAKE SW IN	OFF
BREAK WARN LAMP STATE	ON
HYDRAULIC PUMP MOTOR	OFF
HYDRAULIC PUMP MOTOR	OFF
LF ABS OUT VALV	OFF
LF ABS OUT VALV	OFF
LF WHEEL SPD SENS	O KPH

Current Data B 

This live data show the hydraulic pump motor is switches off, while the ABS system is operating, one wheels shows is lock up this could switches on ABS control relay and relay pump motor. The problem we face with this vehicle is both rear wheel sensor give out fault to the scan. 

Actuator TEST

Testing our ABS pump we used the Autoboss tool, this activate the pump relay and solenoid even the vehicle is shot off. Giving demand or actuation on the scan tool is perfect way to check system, diagnoses and analyse other programs.

The test we working on today is to check the ABS actuator and see if it work. When we test solenoids we can hear the clicking sound once they activate, we used the scan tool to switch it on/off. when this happen the solenoid click and so they work. If the solenoid dosen't click than we can identify it as fault.