Troubleshooting - Toyota 4A-FE Repair Manual

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EFI SYSTEM - Troubleshooting
FI0402
TROUBLESHOOTING
TROUBLESHOOTING HINTS
1. Engine trouble are usually not caused by the EFI system.
When troubleshooting, always firstly check the condition
of the other systems.
(a) Electronic source
• Battery
• Fusible links
• Fuses
(b) Body ground
(c) Fuel supply
• Fuel leakage
• Fuel filter
•Fuel pump
(d) Ignition system
• Spark plugs
• High-tension cords
• llA or Distributor
• Ignition coil
• Igniter
(e) Air induction system
• Vacuum leaks
(f)
Emission control system
• PCV system
• EGR system (w/ EGR system)
(g) Others
• Ignition timing
• Idle speed
• etc .
2. The most frequent cause of problems is simply a bad con-
tact in wiring connectors. Always check that connections
are secure.
When inspecting the connector, pay particular attention to
the following points:
{a) Check to see that the terminals are not bent.
(b) Check to see that the connector is pushed in com-
pletely and locked.
(c)
Check to see that there is no signal change when the
connector is slightly tapped or wiggled. ·
3. Sufficiently troubleshooting for other causes before rep-
lacing the ECU, as the ECU is high quality and expensive.