G420E/G424E
Tier
LP Engine
Advanced Diagnostics
59
Table a. MI-04 Diagnostic Fault Codes (Flash Codes)
DFC
Probable Fault
Action
Corrective Action, First Check
74 O2SensorSwitching
O2 sensor is not switching across the
reference AFR voltage
Stored Fault Code
(MIL, Disable Adaptive
learns)
Check the FTV for proper operation
z
Check FTV Hose Connections
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)
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.
77 OxygenSensorInputHigh
O2 sensor SECM driver signal is
shorted to power
Stored Fault Code
(MIL, Disable Adapts)
Check if O2 sensor is shorted to
+5VDC or Battery.
O2 (SIGNAL) PIN B to SECM PIN 3
(AFRTrimValveLowerDC fault should
also occur)
Verify O2 sensor heater circuit is
operating by measuring circuit
resistance
(2.1
Ω
+/-0.4
Ω
)
O2 PIN C (HEATER GND) to PIN D
(HEATER PWR)
