YH4
GRAND
VITARA
ENGINE DIAGNOSIS (G16/J20 ENGINES) 6-11
PRECAUTION IN DIAGNOSING TROUBLE
Don’t disconnect couplers from ECM (PCM), battery cable from battery, ECM (PCM) ground wire harness from
engine or main fuse before confirming diagnostic information (DTC, freeze frame data, etc.) stored in ECM (PCM)
memory.
Diagnostic information stored in ECM (PCM) memory can be cleared as well as checked by using SUZUKI scan
tool (Tech-1) or generic scan tool. 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.
Priorities for diagnosing troubles (Vehicle without monitor connector)
If two or more diagnostic trouble codes (DTCs) are stored, proceed to the flow table of the DTC which has de-
tected earliest in the order and follow the instruction in that table.
If no instructions are given, troubleshoot diagnostic trouble codes according to the following priorities.
(1)Diagnostic trouble codes other than fuel trim malfunction (DTC P0171, P0172), EGR (DTC P0400), and mis-
fire (DTC P0300 ~ P0304).
(2)Fuel trim malfunction (DTC P0171, P0172) and EGR (DTC P0400).
(3)Misfire (DTC P0300 ~ P0304)
Be sure to read “Precautions for Electrical Circuit Service” in Section 0A before inspection and observe what is
written there.
ECM (PCM) replacement or substitution
When substituting a known-good ECM, check for following conditions. Neglecting this check may cause damage
to known-good ECM.
– Resistance value of all relays, actuators is as specified respectively.
– MAF sensor, MAP sensor and TP sensor are in good condition and none of power circuits of these sensors
is shorted to ground.
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