Mitsubishi Eclipse. Technical Information Manual (1994) - part 69

 

   ABS 

INITIAL CHECK FUNCTION

The ECU always performs an initial check on the
ABS system with the on-board diagnostic function.

1. Initial Check Operation
(1) When the ignition key is placed in the ON posi-

tion, the power is supplied to the ABS-ECU,
and the ABS-ECU starts a diagnostic sequence.

During the diagnostic period, the ABS valve
relay stays in the “OFF” state and the warning
light continues to light.

(2) Then, the ABS-ECU forces the ABS valve relay

into the “ON” state and executes diagnostic test
mode of the ABS valve relay to detect an ON
or OFF failure.

(3) All the solenoid valves are caused to be ON

and OFF to make sure that the valves are not
sticking.

If it detects an error, it illuminates the warning light,

and disables the ABS system.

(4) If the engine starts and the ignition key is re-

turned to the “ON” position, the ABS-ECU power

supply is resumed, and initial checks in (1)

through (3) are performed again.

(5) When the initial checks are satisfactorily com-

pleted, the ABS becomes ready for operation.

NOTE
An operation check for the motor relay and the motor
is performed when the vehicle is put in motion after
starting the engine. This check is performed only
once whenever the ignition switch is turned “ON”.

START

Ignition key 

ACC

ABS-ECU

power supply

. 

ABS

warning light

ABS valve 

relay

Solenoid ON
valve

OFF

 

   ABS 

FAIL-SAFE FUNCTION

Should a failure occur in the ABS system, the 

ECU isolates the system to retain the vehicle’s ordi-
nary braking function, thus assuring a high measure

of safety.

l 

If the ABS-ECU determines that the system

is defective as the result of diagnostic test mode,

DIAGNOSTIC FUNCTIONS

To facilitate inspection of the ABS system, the 

ECU offers the following facilities:

l

Diagnostic trouble code output and erasure

l 

Actuator test

All of the items described above can be checked
by the scan tool.

Scan Tool

 ABS Interface

The scan tool function is entered by connecting
the scan tool to the data link connector. At this time,

it causes the ABS warning light to light, drives
the valve relay to interrupt control of the solenoid
valves in the HU, and restores the ordinary brak-
ing mode.

the vehicle must be stopped, and the ignition should

be OFF.

The ABS scan tool mode is entered when you select
the ABS system on the scan tool. In this mode,

diagnostic output, data list output and actuator test

functions are available. During an actuator test, how-

ever, the ABS warning light illuminates and anti-lock
control is inhibited to prevent ABS operation when
a brake is temporarily inactivated during the actuator

Scan tool

 Wheel speeds of 0 km/h (0 mph), parked 

mode entry

tion

condition

 Check harness of scan tool connected to data

link connector of vehicle

 ABS system selected by control switch of scan

tool (Specified serial data received)

NOTE
No communications with the ABS-ECU can be made by con-
necting the scan tool while the vehicle is in operation [wheel
speeds not 0 km/h (0 mph)].

 

   ABS 

Diagnostic Trouble Codes

Conditions detected as a result of diagnosis are
associated with a total of 14 codes including that

for normal state, and the codes are stored in the
volatile memory.

Even if the ignition key is placed in the “OFF” 

tion, the contents of the memory are not cleared,
as the memory remains powered by a backup power

These codes are readable by connecting the scan

When the scan tool is not used, they are also 
able with a voltmeter which deflects in a pattern

unique to each code.

1. Diagnostic items, diagnostic codes and detection condition

Detection

Code No. display

Inspection item

on Scan tool

Diagnostic content

tions

A B

Front right wheel speed sensor

Front left wheel speed sensor

Rear right wheel speed sensor

Open circuit or short in   wire

x x

Rear left wheel speed sensor

Wheel speed sensor system

Abnormal output signal

X

21

G sensor

Broke wire in G sensor or OFF mal-

function

X

Stop light switch system

Open circuit or ON malfunction

X

41

Front left solenoid valve

No response to solenoid valve drive

42

Front right solenoid valve

signal

X

43

51

55

No fault code

displayed

Rear solenoid valve

Valve relay

Motor relay or Motor

ABS-ECU

(The system is in order)

Current value in both valves is differ-
ent when in same mode

X

Valve relay OFF failure

x x

Motor relay OFF failure and motor

drive failure

X

ABS-ECU internal failure (program

maze, etc)

 

Detection conditions

A: During system check immediately after staritng

B: During operation

DRIVE-CONTROL COMPONENTS   ABS 

NOTE

 The ABS-ECU can detect only an open circuit from the moment the ECU power supply is ON.

The ABS-ECU lights the ABS warning light when it detects an open circuit, but it does not immediately store
the trouble code in memory and does not cause the system to shut down.
When an open circuit is detected, the trouble code is stored in memory and the system caused to shut down
when the vehicle starts and the wheel speed reaches 6 km/h (4 mph) (the first acceleration after the 

 has

been placed in the ON state).

Troubles other than an open circuit cannot be detected until the wheel speed reaches 6 km/h (4 mph). When
the ABS-ECU detects any of these troubles, it causes the system to shut down and simultaneously lights the
ABS warning light.

The shut down 

 time varies with the wheel speed as described below.

First start after engine start:

l

When the wheel speed is less than 10 km/h (6 mph), the system shuts down 60 seconds later.

l

When the wheel speed is 10 km/h (6 mph) or more, the system shuts down immediately.

Restart:

l

When the wheel speed is less than 20 km/h (12 mph), the system shuts down 60 seconds later.

l

When the wheel speed is 20 km/h (12 mph) or more, the system shuts down immediately.

When the ABS-ECU detects a wheel speed sensor error during ABS control, it causes the system
to come down and simultaneously lights the ABS warning light after ABS control.

 The ABS-ECU takes more than 15 minutes from when it detects an error to when it determines that the fault

has occurred.

 The ABS-ECU makes an initial check on the motor relay and motor when the wheel speed reaches 6 km/h

(4 mph) for the first time after engine start. If anything wrong is detected, it causes the system to shut down
and simultaneously lights the ABS warning light.