Dtc 1151-Closed Loop High (Lpg); Dtc 1153-Closed Loop High (Ng) - Kubota WG1605-E3 Diagnostic Manual

WG1605-G-E3,WG1605-L-E3,WG1605-GL-E3, DM
The HEGO/HO S sensor is a switching-type sensor around stoichiometry that measures the oxygen content
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present in the exhaust to determine if the fuel flow to the engine is correct. A UEGO sensor measures the exhaust
content across a wide-range of air-fuel ratios with a linear output proportional to lambda/equivalence ratio/air-fuel
ratio. In either case, if there is a deviation between the expected reading and the actual reading, fuel flow is precisely
adjusted for each bank using the Closed Loop multiplier and then "learned" with the Adaptive multiplier. The
multipliers only update when the system is in either "CL Active" or "CL + Adapt" control modes. The purpose of the
closed loop fuel multiplier is to quickly adjust fuel flow due to variations in fuel composition, engine wear,
engine-to-engine build variances, and component degradation prior to adaptive learn fueling correction "learning" the
fueling deviation.
The fault of DTC 1151 and DTC 1153 sets if the Closed Loop multiplier exceeds the high limit of normal operation
indicating that the engine is operating lean (excess oxygen) and requires more fuel than allowed by corrections. Often
high positive fueling corrections are a function of one or more of the following conditions: 1) exhaust leaks upstream
or near the HEGO sensor, 2) reduced fuel supply pressure to the gaseous fuel control system, 3) a fuel supply or
manifold leak, 4) a non-responsive HEGO/UEGO sensor, and/or 5) a defective gaseous fuel control component
(actuator/valve and/or mixer). These faults should be configured to disable adaptive learn for the remainder of the
key-cycle to avoid improperly learning the adaptive learn table and may be configured to disable closed loop.
The fault of DTC 1152 and DTC 1154 sets if the Closed Loop multiplier exceeds the low limit of normal operation
indicating that the engine is operating rich (excess fuel) and requires less fuel than allowed by corrections. Often high
negative fueling corrections are a function of one or more of the following conditions: 1) high fuel supply pressure to
the gaseous fuel control or faulty pressure regulator and/or 2) a non-responsive HEGO/UEGO sensor. These faults
should be configured to disable adaptive learn for the remainder of the key-cycle to avoid improperly learning the
adaptive learn table and may be configured to disable closed loop.
The fault of DTC 1155 sets if the closed loop multiplier exceeds the high limit of normal operation indicating that
the engine is operating lean (excess oxygen) and requires more fuel than allowed by corrections. Often high positive
fueling corrections are a function of one or more of the following conditions: 1) exhaust leaks upstream or near the
HEGO sensor, 2) reduced fuel supply pressure to the fuel injection system, 3) a non-responsive HEGO/UEGO
sensor, and/or 3) an injector that is stuck closed. This fault should be configured to disable adaptive learn for the
remainder of the key-cycle to avoid improperly learning the adaptive learn table and may be configured to disable
closed loop.
The fault of DTC 1156 sets if the closed loop multiplier exceeds the low limit of normal operation indicating that
the engine is operating rich (excess fuel) and requires less fuel than allowed by corrections. Often high negative
fueling corrections are a function of one or more of the following conditions: 1) high fuel supply pressure to the fuel
injection system, 2) a non-responsive HEGO/UEGO sensor, and/or 3) an injector that is stuck open. This fault should
be configured to disable adaptive learn for the remainder of the key-cycle to avoid improperly learning the adaptive
learn table and may be configured to disable closed loop.

DTC 1151-Closed Loop High (LPG)

DTC 1153-Closed Loop High (NG)

Diagnostic Aids
NOTE
• If any other DTCs are present, diagnose those first.
• Oxygen Sensor Wire - Sensor may be mispositioned contacting the exhaust. Check for short to ground between
harness and sensor sense signal.
• Vacuum Leaks - Large vacuum leaks and crankcase leaks can cause a lean exhaust condition at light load.
• Fuel Pressure - System will be lean if fuel pressure is too low. Ensure fuel tank pressure is not too low and that
gaseous fuel control actuator/regulator has proper fuel pressure under all operating conditions.
• Exhaust Leaks - If there is an exhaust leak, outside air can be pulled into the exhaust and past the O
causing a false lean condition.
• Fuel Quality - A drastic variation in fuel quality may cause the system to be lean including fuels with high inert gas
content.
• System Grounding - ECM and engine must be grounded to the battery with very little resistance allowing for
proper current flow. Faulty grounds can cause current supply issues resulting in many undesired problems.
• If all tests are OK, replace the HO S or UEGO sensor with a known good part and retest.
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ECM SYSTEM
sensor
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KiSC issued 12, 2016 A