DTC P1124,1128, or P0170 (Positive Fuel Trim Numbers

(The PCM is increasing fuel delivery to compensate for a "Lean" condition)

^ Check for vacuum or unmetered air leaks, concentrating on areas between the air flow sensor and the engine block. Are all the gaskets and hoses properly installed? A vehicle with a vacuum leak will have an air flow sensor reading that is lower than normal at idle (see Air Flow Sensor Table in this TSB). Accent, Elantra and Tiburon vehicles with a vacuum leak may also have a low load value.

^ Check the evaporative emission system. An intermittently sticking or stuck open purge solenoid valve may not set an evaporative code in a 1996 or 1997 SOHC Accent or Sonata, but may set a Fuel Trim code.





Check the air flow sensor calibration. If no vacuum leaks are present and the purge system is functioning properly, compare the air flow sensor reading at idle and at 2500 rpm to the Air Flow Sensor Table. If readings are out of specification, swap the air flow sensor with a known good unit and re-test.

^ Check the fuel pressure (for low pressure), fuel volume flow (replace fuel filter if necessary), injector part number, PCM part number and perform the oxygen sensor scan tool test as noted in this TSB.