Download 1997 Mazda 626 ES Engine Performance’ ‘Self-Diagnostics – 2.0L – A/T – DTC P0171, P0172, P1130, P1131 OR P1132 – FUEL CONTROL, HO2S NOT SWITCHING NOTE: For connector identification, see CONNECTOR IDENTIFICATION . For wiring diagram, see L – WIRING DIAGRAMS – 2.0L article. Diagnostic Aids Perform this test when instructed during QUICK TEST or if directed by other test procedures. Only use this test to diagnose the following: HO2S and sensor connection. Vacuum systems. Fuel injector and/or fuel injector circuitry. Powertrain Control Module (PCM). Electrical circuits (HO2S, HO2S GND, INJ 1-4, VPWR and SIG RTN). NOTE: To prevent replacement of good components, be aware, the following non-EEC areas may be cause of driveability concerns: Ignition system. Faulty evaporative emission system. EGR and/or PCV system. Air intake system. Engine oil contamination. Fuel system. Exhaust system leaks or restriction. Engine cooling system. 1)HO2S Not Switching DTC P1131 indicates air/fuel ratio is correcting rich for an overly lean condition. DTC P1132 indicates air/fuel ratio is correcting lean for an overly rich condition. DTC P1130 indicates fuel system has reached maximum compensation and HO2S is not switching at the adaptive limits. Possible causes are as follows: Fuel system malfunction. EGR system malfunction. Air intake or vacuum system leak. Engine oil level too high. Excessive internal engine wear. HO2S may be displayed on scan tool as 02S.