ENGINE DIAGNOSIS
6-15
Condition
Possible Cause
Referring Item
Excessive
hydrocarbon (HC)
emission or
Excessive carbon
monoxide (CO)
emission
Ignition system out of order
Defective spark plug
Fuel system out of order
Fuel pressure out of specification
Engine and Emission control system
out of order.
Lead contamination of three way catalytic
converter (if equipped)
Malfunctioning PCV valve
Faulty EVAP control system
Closed loop system (A / F feed back
compensation) fails
– Faulty TP sensor
– Faulty ECT sensor or MAP sensor
– Faulty O
2
sensor
Faulty injector
Faulty ECM
Low compression
Fuel pressure check in Section 6E1.
Check for absence of filler neck
restrictor.
PCV valve in Section 6E1.
EVAP control system check in
Section 6E1.
Check oxygen sensor output voltage
referring to DTC No.14 Diag. Flow
Table in Section 6E1.
Fuel injector in Section 6E1.
Inspection of ECM and its circuit in
Section 6E1.
Previously outlined.
Excessive nitrogen
oxides (NOx)
emission
Fuel system out of order
Fuel pressure out of specification
Engine and emission control system
Lead contamination of three way catalytic
converter (if equipped)
Closed loop system (A / F feed back
compensation) fails (vehicle with O
2
sensor)
– Faulty TP sensor
– Faulty ECT sensor or MAP sensor
– Faulty O
2
sensor
Faulty injector
Faulty ECM
Fuel pressure check in Section 6E1.
Check for absence of filler neck
restrictor.
Check oxygen sensor output voltage
referring to DTC No.14 Diag. Flow
Table in Section 6E1.
Fuel injector Section 6E1.
Inspection of ECM and its circuit in
Section 6E1.