Suzuki GRAND VITARA JB416, Service Manual

Page: 19 / 474

Engine General Information and Diagnosis: 1A-1
Engine General Information and Diagnosis
Precautions
Precautions in Diagnosing Trouble
S5JB0E1100002
• Don’t disconnect couplers from ECM, battery cable
from battery, ECM ground wire harness from engine
or main fuse before confirming diagnostic information
(DTC, freeze frame data, etc.) stored in ECM memory.
Such disconnection will erase memorized information
in ECM memory.
• Diagnostic information stored in ECM memory can be
cleared as well as checked by using SUZUKI scan
tool or OBD generic scan tool (Vehicle without
diagnosis connector). Before using scan tool, read its
Operator’s (Instruction) Manual carefully to have good
understanding as to what functions are available and
how to use it.
It is indistinguishable which module turns on MIL
because not only ECM but also TCM (for A/T model)
turns on MIL (For details of on-board diagnostic
system for A/T model, refer to “On-Board Diagnostic
System Description: in Section 5A in related manual”.
Therefore, check both ECM and TCM (for A/T model)
for DTC when MIL lights on.
When checking ECM for DTC, keep in mind that DTC
is displayed on the scan tool as follows depending on
the scan tool used.
– SUZUKI scan tool displays DTC detected by ECM.
– OBD generic scan tool displays DTC detected by
each of ECM and TCM (for A/T model)
simultaneously.
• Priorities for diagnosing troubles
If two or more DTCs are stored, proceed to the DTC
flow which has been detected earliest in the order and
follow the instruction in that flow.
If no instructions are given, troubleshoot DTCs
according to the following priorities.
a. DTCs other than DTC P0171 / P0172 (Fuel
system too lean / too rich), DTC P0300 / P0301 /
P0302 / P0303 / P0304 (Misfire detected) and
DTC P0401 / P0402 (EGR flow malfunction)
b. DTC P0171 / P0172 (Fuel system too lean / too
rich) and DTC P0401 / P0402 (EGR flow
malfunction)
c. DTC P0300 / P0301 / P0302 / P0303 / P0304
(Misfire detected)
• Be sure to read “Precautions for Electrical Circuit
Service: in Section 00 in related manual” before
inspection and observe what is written there.
• ECM replacement:
When substituting a known-good ECM, check for the
following conditions. Neglecting this check may cause
damage to a known-good ECM.
– Resistance value of all relays and actuators is as
specified respectively.
– MAP sensor, electric load current sensor (for J20
engine), A/C refrigerant pressure sensor (if
equipped with A/C), accelerator pedal position
(APP) sensor, TP sensor and CO adjust resistor (if
not equipped with A/F sensor) are in good condition
and none of power circuits of these sensors is
shorted to ground.
• Communication of ECM, BCM, combination meter,
keyless start control module (if equipped), ABS /
ESP
®
control module, 4WD control module (if
equipped), steering angle sensor (if equipped) and
TCM (for A/T model) is established by CAN
(Controller Area Network). (For more detail of CAN
communication for ECM, refer to “CAN
Communication System Description: ”). Therefore,
handle CAN communication line with care referring to
“Precaution for CAN Communication System: in
Section 00 in related manual”.
• Immobilizer transponder code registration after
replacing ECM:
When ECM is replaced with new one or with another
one, make sure to register immobilizer transponder
code with ECM correctly according to “Procedure after
ECM Replacement: in Section 10C in related
manual”.