Couldnt find anything on code 31?

Code 71
AFRTrimValveOutput
FTV modulation driver signal fault
Stored Fault Code
(MIL, Disable Adaptive
learns)

Check FTV for an open wire or FTV connector being
disconnected

FTV PIN A (SIGNAL) to PIN B (PWR)
Check FTV for an open coil by disconnecting the
FTV connector and measuring the resistance
(~26Ù +/-2Ù)

FTV PIN A (SIGNAL) to PIN B (PWR)

Code 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 4 (SIGNAL) to PIN B (PWR)

Check FTV for an open coil by disconnecting the
FTV connector and measuring the resistance
(~26Ù +/-2Ù)

FTV PIN A (SIGNAL) to PIN B (PWR)
* Check N-CA55-500-TR mixer for heavy end
build-up and operation (see mixer section)
* Check N2001 secondary for operation (see N2001 Regulator section)

Code 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
* Check FTV Hose Connections

Check FTV for an open coil by disconnecting the
FTV connector and measuring the resistance
(~26Ù +/-2Ù)

FTV PIN A (SIGNAL) to PIN B (PWR)