The following provides troubleshooting instructions applicable to these fault codes.
522655-1 = Short Term Closed Loop Fuel Correction greater than 40% (Lean Engine Operation)
522660-1 = Long Term Closed Loop Fuel Correction greater than 35% (Lean Engine Operation)
Closed Loop Fuel System Operation: Basically, the fuel injector responds to rich fuel conditions
with a LOW duty cycle to reduce the fuel entering the intake. It responds to lean conditions with a
HIGH duty cycle to increase the fuel entering the intake. The actual fuel mixture is sensed by the O2
sensor which provides this input to the ECU which in turn directs the correct output to the fuel injector
to maintain a normal O2 sensor voltage of 0.2 - 0.8 volts.
Short Term and Long Term Fuel Correction: Under various engine conditions, there is a NORMAL
correction that is required (known as adaptive learn or long-term closed-loop fuel correction) that is
stored in the ECU and learned after operation of the engine for 1 2 hrs. The learned correction
should closely match the calibrated values that were established and tested in the original design of
the fuel system. This would result in adaptive learn (long-term closed loop fuel correction) values of
0%. However, several factors can affect the actual fuel mixtures, including tolerances in the mixer and
regulator, and maintenance issues involving filters and fuel contamination. These items can cause the
fuel correction to exceed the acceptable limits and eventually result in a fault code.
Possible Causes for Lean Fuel Mixture DTCs: Factors that may cause DTCs 522655-1 and
522660-1 are vacuum leaks, exhaust leaks and low fuel pressure due to dirty or clogged fuel filters.
Additional factors could be regulators, mixers, fuel injectors that have been contaminated by heavy
particulates in the LPG fuel or defective fuel injectors that do not open properly.