Note. For circuit reference (Схема №6)
Circuit Description
PCM provides about .45 volt reference to Heated Oxygen Sensor (HO2S). HO2S sensor signal varies from about one volt when exhaust is rich to about .1 volt when exhaust is lean. PCM reads and stores sensor reading information during normal closed loop operation and evaluates the reading samples to determine amount of time sensor reading is out of range. If HO2S-1 reading is out of predetermined range, DTC will set.
Conditions required to set DTC are
- No related DTCs set.
- ECT is above 140°F (60°C).
- Closed loop commanded air/fuel ratio is 14.5-14.8:1.
- TP angle is 3-19%.
- Front HO2S signal remains above 952 mV during normal closed loop operation for 77 seconds over a 90-second period.
- Front HO2S signal stays above 500 mV during deceleration fuel cut-off mode operation for 5 seconds.
Diagnostic Aids
Ensure front HO2S harness is routed correctly and not contacting exhaust system. Check for open or short in front HO2S or ground circuits. Check for internally shorted front HO2S. Check front HO2S for silicon (powdery white deposit) contamination. Check for faulty PCM grounds. Perform FUEL SYSTEM DIAGNOSIS under appropriate TROUBLE SHOOTING in BASIC TESTING article. Perform FUEL INJECTOR BALANCE TEST under FUEL SYSTEM in SYSTEM & COMPONENT TESTS article.
Check EVAP canister for fuel saturation. Disconnect MAF sensor connector and see if rich condition is corrected. If rich condition is corrected, check MAF sensor. Check for fuel in fuel pressure regulator vacuum line. Check TP sensor output for false information causing the fuel system to go rich. Inspect for silicon contamination of HO2S, causing high HO2S-1 voltage signal.