Dynalco AF-900PC Air/Fuel Ratio Controller - Manual (Page 51)

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When CONTROL LIMIT comes on during operation, it indicates that the AF900PC
cannot apply sufficient valve movement to obtain the desired air/fuel ratio under the
existing operating conditions. In this case, the engine’s fuel pressure regulator
spring or carburetor will have to be adjusted. If CONTROL LIMIT and LEAN are
on, the AF900PC output fuel valve is wide open and cannot increase fuel flow to
meet the O2 sensor setpoint. In this case the fuel pressure regulator spring
pressure must be increased or the carburetor enriched. If CONTROL LIMIT and
RICH are on, the AF900PC cannot decrease fuel flow enough to meet the O2
sensor setpoint. This would be unlikely and could be caused by a fuel valve
malfunction.
20. Diagnostics
The AF900PC has powerful self-diagnostics to detect and properly deal with
system and sensor faults. Below is a list of possible faults for which trips can be
enabled:
Post-Catalyst O
2
Sensor Fault
Param #7093
Sensor reading is outside normal range of 0 – 1V
Post-Catalyst O
2
Sensor Health
Param #950
Sensor health is degraded – time to replace
Post-Catalyst Thermocouple Fault
Param #7094
Thermocouple open or reading is outside valid range
Post-Catalyst Temperature Low
Param #7025
Temperature after the catalytic converter is too low
Post-Catalyst Compensation Limit
Param #7096
The post-catalyst compensation is at its maximum
Left Bank Pre-Catalyst O
2
Sensor Fault
Param #7232.1
Sensor reading is outside normal range of 0 – 1V.
Left Bank Pre-Catalyst O
2
Sensor Health
Param #950.1
Sensor health is degraded – time to replace.
Left Bank Pre-Catalyst Thermocouple Fault
Param #7233.1 Thermocouple open or reading is outside valid range.
Left Bank Pre-Catalyst Temperature Low
Param #7120.1
Temperature before the catalytic converter on left
bank is too low