Diagnosis; On-Board Diagnostic System; Precautions In Diagnosing Troubles - Suzuki Canvas SQ416 Service Manual

6E1-4 ENGINE AND EMISSION CONTROL SYSTEM (G16 / J20 ENGINE)

DIAGNOSIS

The engine and emission control system in this vehicle are con-
trolled by ECM/PCM. ECM/PCM has an On-Board Diagnostic sys-
tem which detects a malfunction in this system.
When diagnosing troubles, be sure to have full understanding of the
outline of "On-Board Diagnostic System" and each item in "Precau-
tion in Diagnosing Trouble" and execute diagnosis according to
"Engine Diagnostic Flow Table" in Section 6.

ON-BOARD DIAGNOSTIC SYSTEM

ECM/PCM performs on-board diagnosis (self-diagnosis) on the
system and operates "CHECK ENGINE" lamp (malfunction indica-
tor lamp) as follows.
Malfunction indicator lamp ("CHECK ENGINE" light) lights when
the ignition switch is turned ON (but the engine at stop) regardless
of the condition of Engine and emission control system. This is
only to check the malfunction indicator lamp ("CHECK ENGINE"
light) bulb and its circuit.
If the areas monitored by ECM/PCM is free from any trouble after
the engine start (while engine is running), malfunction indicator
lamp ("CHECK ENGINE" light) turns OFF.
When ECM/PCM detects a trouble which has occurred in the
areas, it makes malfunction indicator lamp ("CHECK ENGINE"
light) turn ON while the engine is running to warn the driver of such
occurrence of trouble and at the same time it stores the exact
trouble area in ECM/PCM back-up memory.

PRECAUTIONS IN DIAGNOSING TROUBLES

Before identifying diagnostic trouble code, don't disconnect cou-
plers from ECM/PCM, battery cable from battery, ECM/PCM
ground wire harness from engine. Such disconnection will erase
memorized trouble in ECM/PCM memory.
Be sure to read "Precautions for Electrical Circuit Service" in Sec-
tion 0A before inspection and observe what is written there.
ECM/PCM replacement
When substituting a known-good ECM/PCM, check for following
conditions. Neglecting this check may cause damage to known-
good ECM/PCM.
– Resistance value of all relays, actuators is as specified re-
spectively.
– TP sensor and fuel tank pressure sensor (if equipped) are in
good condition and none of power circuits of these sensors is
shorted to ground.