Engine Diagnosis General Description; On-Board Diagnostic System Description - Suzuki Grand Vitara Service Manual

1A-3 Engine General Information and Diagnosis:

Engine Diagnosis General Description

This vehicle is equipped with an engine and emission
control system which are under control of ECM.
The engine and emission control system in this vehicle
are controlled by ECM. ECM has an On-Board
Diagnostic system which detects a malfunction in this
system and abnormality of those parts that influence the
engine exhaust emission. When diagnosing engine
troubles, be sure to have full understanding of the outline
of "On-Board Diagnostic System Description: " and each
item in "Precautions in Diagnosing Trouble: " and
execute diagnosis according to "Engine and Emission
Control System Check: ".
There is a close relationship between the engine
mechanical, engine cooling system, ignition system,
exhaust system, etc. and the engine and emission
control system in their structure and operation. In case of
an engine trouble, even when the malfunction indicator
lamp (MIL) doesn't turn ON, it should be diagnosed
according to "Engine and Emission Control System
Check: ".

On-Board Diagnostic System Description

Vehicle not Equipped with Diagnosis Connector
ECM in this vehicle has the following functions.
• When the ignition switch is turned ON with the engine
at a stop, malfunction indicator lamp (MIL) (1) turns
ON to check the circuit of the malfunction indicator
lamp (1).
• When ECM detects a malfunction which gives an
adverse effect to vehicle emission while the engine is
running, it makes the malfunction indicator lamp (1) in
the meter cluster of the instrument panel turn ON or
flash (flashing only when detecting a misfire which
can cause damage to the catalyst) and stores the
malfunction area in its memory.
(If it detects that continuously 3 driving cycles are
normal after detecting a malfunction, however, it
makes MIL (1) turn OFF although DTC stored in its
memory will remain.)
• As a condition for detecting a malfunction in some
areas in the system being monitored by ECM and
turning ON the malfunction indicator lamp (1) due to
that malfunction, 2 driving cycle detection logic is
adopted to prevent erroneous detection.
• When a malfunction is detected, engine and driving
conditions then are stored in ECM memory as freeze
frame data. (For the details, refer to description on
"Freeze Frame Data (Vehicle Not Equipped with
Diagnosis Connector): ".)
• It is possible to communicate by using not only
SUZUKI scan tool (2) but also OBD generic scan tool.
(Diagnostic information can be accessed by using a
scan tool.)
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3. DLC
Vehicle Equipped with Diagnosis Connector
ECM diagnosis troubles which may occur in the area
including the following parts when the ignition switch is
ON and the engine is running, and indicates the result by
turning on or flashing malfunction indicator lamp (1).
• A/F sensor (if equipped)
• Heated oxygen sensor (if equipped)
• ECT sensor
• TP sensor
• MAF sensor
• IAT sensor
• MAP sensor
• CMP sensor
• CKP sensor
• Knock sensor
• Wheel speed sensor
• CPU (Central Processing Unit) of ECM
• APP sensor
• Oil control valve (for M16 engine)
• Radiator cooling fan relay
ECM and malfunction indicator lamp (1) operate as
follows.
• Malfunction indicator lamp (1) lights when the ignition
switch is turned ON (but the engine at stop) with the
diagnosis switch terminal ungrounded regardless of
the condition of Engine and Emission control system.
This is only to check the malfunction indicator lamp (1)
in the combination meter and its circuit.
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