Service manual

G420F(FE) Service Manual 250 Chapter 8. Basic Troubleshooting
Basic Inspection Procedure
Measuring Condition Of Electronic Parts
Resistance
The measured resistance at high temperature after
vehicle running may be high or low. So all resistance
must be measured at ambient temperature (20℃, 68
℉), unless there is any notice.
NOTE: The measured resistance in except for
ambient temperature (20℃, 68℉) is reference value.
Intermittent Problem Inspection Procedure
Sometimes the most difficult case in troubleshooting
is when a problem symptom occurs but does not
occur again during testing. An example would be if a
problem appears only when the vehicle is cold but
has not appeared when warm. In this case,
technician should thoroughly make out a
"CUSTOMER PROBLEM ANALYSIS SHEET" and
recreate (simulate) the environment and condition
which occurred when the vehicle was having the
issue.
1. Clear Diagnostic Trouble Code (DTC).
2. Inspect connector connection, and check terminal
for poor connections, loose wires, bent, broken or
corroded pins, and then verify that the connectors
are always securely fastened.
3. Slightly shake the connector and wiring harness
vertically and horizontally.
4. Repair or replace the component that has a
problem.
5. Verify that the problem has disappeared with the
road test.
● SIMULATING VIBRATION
1) Sensors and Actuators
: Slightly vibrate sensors, actuators or relays
with finger.
WARNING
Strong vibration may break sensors, actuators
or relays.
2) Connectors and Harness
: Lightly shake the connector and wiring
harness vertically and then horizontally.
● Simulating Heat
1) Heat components suspected of causing the
malfunction with a hair dryer or other heat
sourre.
WARNING
DO NOT heat components to the point where
they may be damaged.
DO NOT heat the ECM directly.
● Simulating Water Sprinkling
1) Sprinkle water onto vehicle to simulate a rainy
day or a high humidity condition.
WARNING
DO NOT sprinkle water directly into the engine
compartment or electronic components.
● Simulatingelectricalload
1) Turn on all electrical systems to simulate
excessive electrical loads (Radios, fans, lights,
etc.).