Posted on January 18, 2009 - by Richard

To Fix Oxygen Sensor Circuit Can Help You Save Gas

Understanding the methods to fix oxygen sensor comes handy when tuning up oxygen sensor circuits. Since oxygen sensor mainly control the fuel mixture of the engine by measuring the oxygen content parameter for the engine computer (ecm), it is necessary for us to understand how this sensor circuits works.

In the early 1980s when oxygen sensor was first introduced, it has only one signal wire. This sensitive wire was designed so that it only takes low voltage signal under 1 volt. This crude design has a major flaw; it takes too much time for the sensor to give signal to the engine computer.

It is the computer’s job to regulate the fuel mixture after the sensor warms up which sometimes takes about 10-15 minutes. This time delay can gets worse when the weather gets cold and would dump a lot of raw fuel to the catalytic converter (CAT). This leads to premature CAT failure and high fuel consumption.

Since 1994-2006, the oxygen sensor has been upgraded to resolve this problem:

1.) The introduction of the heating circuit within the sensor to make it warm faster

In the old single wire design, the sensor needs time to warm up before it can give voltage signals to the ecm (called open loop) this creates not only waste in fuel efficiency but could cause early downgrading of the catalytic converter which it needs to protect. To resolve this, two oxygen sensors were added before and after the catalytic converter which included a heating element on each of them.

Looking at the sensor wiring connection, it has 3-4 wires on each sensor in which the ecm can gets 1-2 variable voltage signal wires and an extra wire for the heater element. This resulted in closer monitoring of fuel because the sensor is heated almost right away and better reaction times from the ecm regardless of weather conditions.

2.) The introduction of zircona or the wide band oxygen sensor

This was adopted in 2001-2006 but only on limited vehicles. An electric and chemical gas pump current was added to the sensor signal circuit which gives a constant voltage feedback. Unlike the earlier types of oxygen sensor where the voltage signal fluctuates between 0.2 to 0.8 volt, this voltage oscillation is eliminated. The ECM pumps current through oxygen sensor (02) signal resistor wire to maintain a certain voltage of 0.45 volt and monitors the current required to maintain that voltage level. Oxygen changes the resistance values in o2 sensor. This process allows faster adjustment of fuel and timing by the ecm at a more rapid rate. Also called UEGO or universal exhaust gas oxygen, it provides quicker response time by the ecm . However, beware when using HHO EFIE adjuster on wide band oxygen sensors because most of them works on short band oxygen sensor only.

These 2 advancements in oxygen sensor designs has lead to improve gas savings because of improved ecm monitoring functionality.

When to fix oxygen sensor circuits:

Common methods to fix oxygen sensor:

1.) Stay away from aftermarket oxygen sensor unless it is made by Bosch.
2.) If you suspect the catalytic converter is plugged, compare 02 voltage readings at idle and wide open throttle (WOT). At WOT, the front and after CAT readings should be the same or slight lower fluctuations after the CAT. Make sure to check with your dealer because CAT is sometimes guaranteed upt0 80k miles.
3.) For those using hho generators, most EFIE adjuster will not work with wide band oxygen sensor. When acting up, the 02 voltage reading could reach higher than 1 volt. Look closer at the 02 signal variable voltage wire: there is a resistor in series for the wide band oxygen sensor.

Thanks,

Richard

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