Impco HHI, Service Manual

Page: 192 / 485

192
DTC 171-Adaptive Learn High (Bi-Fuel/Gasoline Only)
Conditions for Setting the DTC

Heated Oxygen Sensor

Check Condition-Engine Running

Fault Condition-Adaptive multiplier out of range greater than 30%

MIL-On
Circuit Description
The EGO 1 sensor is used to determine if the fuel flow to the engine is correct by measuring
the oxygen content in the exhaust gas. The ECM uses this information to correct the fuel flow
with the Closed Loop multiplier and Adaptive multiplier. This fault will set if the adaptive multip-
lier exceeds the limits of normal operation. Always run the fuel system diagnostic checks
before using the following diagnostic chart.
Diagnostic Aid
Oxygen Sensor Wire Heated Oxygen sensor wires may be mis-routed and contacting the ex-
haust manifold.
Vacuum Leaks Vacuum leaks and crankcase leaks can cause a lean condition at especially
at light load.
Fuel Injectors The system may be lean due to contaminated or faulty fuel injectors
Fuel Pressure Low fuel pressure, faulty fuel regulator or contaminated fuel filter can cause fuel
the system to run lean
Exhaust Leaks If there is an exhaust leak, outside air can be pulled into the exhaust and past
the 02 sensor causing a false lean condition.
Fuel Quality Contaminated or spoiled fuel can cause the fuel system to be lean.
Ground Problem ECM grounds must be clean, tight and in the proper location.