Oxygen Sensor (HEGO)
These have been given many names, all identify the same item on the engine:
• Oxygen Sensor (O2) or (O2S) or (O2′s)
• Exhaust Gas Oxygen Sensor (EGO)
• Heated Oxygen Sensor (HO2)
• Heated Exhaust Gas Oxygen Sensor (HEGOS)
Not all Oxygen sensors are heated, so using the word “heated” might not be correct for your vehicle application.
What is a “Rich Mixture,” “Ideal Mixture,” and a “Lean Mixture” all depends on what conext you use it in. The ideal mixture is the amount of fuel needed to make an engine perform as commanded. A rich mixture is when there is more fuel than needed, and lean mixture is not enough fuel.
The HEGO Sensor detects the presence of oxygen in the exhaust and produces a variable voltage according to the amount of oxygen detected. A high concentration of oxygen (lean air/fuel ratio) in the exhaust produces a low voltage signal less than 0.4 volts. A low concentration of oxygen (rich air/fuel ratio) produces a high voltage signal greater than 0.6 volts. The 02 provides feedback to the computer (EEC) indicating air/fuel ratio in order to achieve a near stoichiometric air/fuel ratio of 14.7:1 during closed loop engine operation. The 02 generates a voltage between 0.0 and 1.1 volts.
|Diagnostic Trouble Code (DTC)||HEGO Location||Fault Definition|
|172 / 41 KOER||Right or Rear||HEGO sensor indicates system lean.|
|136 / 91 KOER||Left or Front|
|176 CM||Left or Front|
|173 / 42 KOER||Right or Rear||HEGO sensor indicates system rich.|
|137 / 92 KOER||Left or Front|
|177 CM||Left or Front|
|144 / 41 CM||Right or Rear||No HEGO sensor switching detected or disconnected.|
|139 / 91 CM||Left or Front|
|171 CM||Right or Rear||Adaptive Fuel Limit reached.|
|175 CM||Left or Front|
All of the following items will cause a HEGO code:
• Check engine oil for fuel contamination.
• Check fuel pressure.
• Check fuel systems ability to hold pressure for 60 seconds.
• Engines general condition.
• Fuel injectors (leaky, stuck, dirty).
• Secondary Air Injection (AIR) system.
• PCV / Hose stuck or blocked.
• Vacuum leaks.
• Fuel Injector O-Rings.
• MAP/MAF sensor.
• Ignition Coil Failure.
• Wiring harness general condition.
• Old HEGO sensors (should be replaced every 60,000 miles).