G420E/G424E
Tier
LP Engine
Advanced Diagnostics
58
Table a. MI-04 Diagnostic Fault Codes (Flash Codes)
DFC
Probable Fault
Action
Corrective Action, First Check
72 AFRTrimValveLowerDC
FTV duty cycle at lower (lean) limit
Stored Fault Code
(MIL, Disable Adaptive
learns)
Engine measured Air/Fuel ratio at the
O2 sensor is excessively lean
z
Check for intake manifold leaks
z
Check balance line (vacuum
hose) connection at the regulator
z
Check N-CA55-500-TR mixer for
heavy end build-up and
operation (see mixer section)
z
Check N2001 secondary for
operation or low primary
pressure (see N2001 Regulator
section)
Note: If LP-Gas fuel in LP tank is not
enough, this fault code can be set. If
LP tank is frozen, this fault code can
be set, too. It is not system trouble.
73 AFRTrimValveUpperDC
FTV duty cycle at high (rich) limit
(Expected fault when FTV connector
is unplugged)
Stored Fault Code
(MIL, Disable Adaptive
learns)
Engine measured Air/Fuel ratio at the
O2 sensor is excessively rich
Check FTV connector wiring for an
open circuit
FTV PIN A (SIGNAL) TO PIN B
(PWR)
Check FTV for an open coil by
disconnecting the FTV connector and
measuring the resistance
(~26
Ω
+/-
2
Ω
)
FTV PIN A (SIGNAL) TO PIN B
(PWR)
z
Check N-CA55-500-TR mixer for
heavy end build-up and
operation (see mixer section)
z
Check N2001 secondary for
operation (see N2001 Regulator
section)
