Kubota WG1605-E3, Diagnostic Manual

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ECM SYSTEM
WG1605-G-E3,WG1605-L-E3,WG1605-GL-E3, DM
1-168
The HEGO/HO
2
S sensor is a switching-type sensor around stoichiometry that measures the oxygen content
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
Adaptive Learn fuel multiplier is to adjust fuel flow due to variations in fuel composition, engine wear, engine-to-engine
build variances, and component degradation.
This fault sets if the Adaptive 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. 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 1161-Adaptive Learn High (LPG)
DTC 1163-Adaptive Learn 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
2
sensor
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
2
S or UEGO sensor with a known good part and retest.
DTC 1162-Adaptive Learn Low (LPG)
DTC 1164-Adaptive Learn Low (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 and on sensor harness
• Fuel Pressure - System will be rich if fuel delivery pressure is too high to gaseous control system. Check fuel
pressure at the control actuator/valve under all operating conditions.
• 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
2
S or UEGO sensor with a known good part and retest.
KiSC issued 12, 2016 A