Description of on-Board Diagnostics
DESCRIPTIONThis specification applies to Hydraulic and Electronic Control Unit (HECU) of the Anti-lock Braking System (ABS) and Traction Control System (TCS).
This HECU has the functions as follows:
^ Input of signal from the wheel speed sensors attached to each wheel.
^ Control of braking force and traction force
^ Fail-safe function
^ Self diagnosis function
^ Interface with the external diagnosis tester
OPERATION
The HECU shall be put into operation by switching on the operating voltage (IGN).
On completion of the initialization phase, the HECU shall be ready for operation.
In the operating condition, the HECU shall be ready, within the specified limits (voltage and temperature), to process the signals offered by the various sensors and switches in accordance with the control algorithm defined by the software and to control the hydraulic and electrical actuators. The HECU shall receive wheel speed signal from the four inductive wheel sensors.
The wheel signals are converted to square wave by the signal conditioning circuit and given as input to the [friction] processor.
The sensor connections shall be monitored for short-circuit and interruption and then in the event of 2 sensor failures, the HECU shall shut down the system.
When one side of the valve coil is connected to the positive voltage that is provided through the valve relay and the other side is connected to the ground by the MOSFET, the solenoid valve goes into operation.
The electrical function of the valves are always monitored by the valve test pulse under normal operation conditions. When overvoltage is detected (above 16 Volts), the HECU switches off the valve relay and shuts down the system. When voltage is returned to operating range, the system goes back to the normal condition after the initialization phase.
In the event of undervoltage (below 10 Volts), ABS control shall be inhibited and the warning lamp shall be turned on.
When voltage is returned to operating range, the warning lamp is switched off and the HECU returns to normal operating mode.
The pump motor operates when the ABS is functioning.
The HECU performs a pump motor test at a speed of 20 km/h once after turned the Ignition switch on. You may hear the motor operate at this time, but it is normal.
Malfunctions or failures detected by the HECU are encoded on the HECU, stored in a EEPROM and read out by diagnostic equipment (hi-scan pro) when the ignition switch is turned on.
WARNING LAMP CONTROL
1. ABS warning lamp module
The ABS warning lamp module indicates the operating condition of the ABS.
The ABS warning lamp is turned on under the following conditions.
^ During the initialization phase after ignition switch ON (3 seconds).
^ In the event of inhibition of ABS functions by failure.
^ When the system ECU is shut down even though ignition power is applied.
^ During diagnostic mode.
^ When the HECU connector is disconnected.
2. EBD warning lamp module
The EBD warning lamp module indicates the operating condition of the EBD. However, in case the parking brake switch is turned on, the EBD warning lamp is always turned on regardless of EBD functions.
The EBD warning lamp is turned on under the following conditions.
^ During the initialization phase after ignition switch ON (3 seconds).
^ When the system ECU is shut down even though ignition power is applied.
^ When the parking brake switch is ON or brake fluid is low level.
^ In the event of inhibition of EBD functions by failure.
3. TCS lamp module
The TCS warning lamp module indicates the operating condition of the TCS.
The TCS warning lamp is turned on under the following conditions:
^ During the initialization phase after ignition switch ON (3 seconds).
^ In the event of inhibition of TCS functions by failure.
^ When the TCS OFF switch is turned on.
TCS function lamp is turned on when the TCS functions are operating (Blinking-2Hz).
DIAGNOSTIC TROUBLE CODE (DTC)
1. If the CPU cannot be activated or the CPU fails, the ABS indicator comes on, but the DTC is not memorized.
2. The memory can hold any number of DTCs. However, when the same DTC is detected more than once, the later one is written over the old one.
Therefore, when the same problem is detected repeatedly, it is memorized as one DTC.
3. The DTCs are indicated in the order they occur.
4. The DTCs are memorized in the EEPROM (non -volatile memory). Therefore, the memorized DTCs cannot be canceled by disconnecting the battery. Perform the specified procedures to erase the DTCs.
SELF-DIAGNOSIS
1. Self diagnosis can be classified into two categories:
^ Initial diagnosis:
Performed right after the engine starts and until the ABS indicator goes off.
^ Regular diagnosis:
Performed right after the initial diagnosis until the ignition switch is turned OFF.
2. When a problem is detected by self-diagnosis, the system:
^ Turns the solenoid valve OFF
^ Turns the pump motor OFF
^ Turns the ABS indicator ON
HOW TO TROUBLESHOOT ABS DTC
The troubleshooting flowchart procedures assume that the cause of the problem is still present and the ABS indicator is still on. Following the flowchart when the ABS indicator does not come on can result in incorrect diagnosis.
1. Question the customer about the conditions when the problem occurred, and try to reproduce the same conditions for troubleshooting. Find out when the ABS indicator came on, such as during initial diagnosis, during ABS control, after ABS control, when vehicle speed was at a certain speed, etc.
2. When the ABS indicator does not come on during the test-drive, but troubleshooting is performed based on the DTC. check for loose connectors, poor contact of the terminals, etc. before you start troubleshooting.
3. After troubleshooting, erase the DTC and test-drive the vehicle. Be sure the ABS indicator does not come on.
HI-SCAN (PRO) CHECK
1. Turn the ignition switch OFF.
2. Connect the Hi-scan (pro) to the 16P data link connector located underneath the lower crash pad panel.
3. Turn the ignition switch ON.
4. Check for diagnostic trouble codes using the Hi-scan (pro).
5. After completion of the repair or correction of the problem, erase the stored fault codes using the clear key on the Hi-scan (pro).
6. Disconnect the Hi-scan (pro) from the 16P data link connector.