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cjawahir wrote:Hook I see that you have 1667 tech post , you of all person should know the reason for using scan tool .
once a check light is on you would get the fault , and then you can work from there.
post the fault code here
cj
cinco wrote:^^ am no
i have a bj 323 wid ah facked o2 sensor for about a year and absolutely no change in fuel efficiency at all
once the car reaches 100k the computer needs the sensor changed once u reset the computer it thinks its changed and there you no more problems.
A lambda sensor's normal life span is 30,000 to 50,000 miles. But the sensor may fail prematurely if it becomes clogged with carbon, or is contaminated by lead from leaded petrol or silicone from an antifreeze leak or from silicone sealer.
As the sensor ages, it becomes sluggish. Eventually it produces an unchanging signal or no signal at all. When this happens, the Check Engine Light may come on, and the engine may experience drivability problems caused by an overly rich fuel condition. Poor fuel economy, elevated CO and HC emissions, poor idle, and/or hesitation during acceleration are typical complaints.
If the average voltage from the lambda sensor is running high (more than 0.50V), it indicates a rich condition, possibly due to a bad MAP, MAF or Air Flow sensor or leaky injector. If the average voltage reading is running low (less than 0.45V), the mixture is running lean possibly due to a vacuum leak or because the sensor itself is bad.
If the lambda sensor continually reads high (rich), it will cause the engine computer to lean out the fuel mixture in an attempt to compensate for the rich reading. This can cause lean misfire, hesitation, stumbling, poor idle and high hydrocarbon emissions (from misfiring).
If the lambda sensor continually reads low (lean), it will cause the engine computer to richen the fuel mixture. Injector pulse width will increase causing fuel consumption and carbon monoxide emissions to go up. Constant rich fuel mixture can also cause the catalytic converter to overheat and it may be damaged.
If the lambda sensor's output is sluggish and does not change (low cross counts & long transition times), the engine computer will not be able to maintain a properly balanced fuel mixture. The engine may run too rich or too lean, depending on the operating conditions. This, in turn, may cause drivability problems such as misfiring, surging, poor idle, and high emissions.
If a heated sensor has a faulty heating circuit or element, the sensor can cool off at idle causing the system to go into open loop. This usually results in a fixed, rich fuel mixture that will increase emissions.
Sometimes an apparent lambda sensor problem is not really a faulty sensor. An air leak in the intake or exhaust manifold or even a fouled spark plug, for example, will cause the lambda sensor to give a false lean indication. The sensor reacts only to the presence or absence of oxygen in the exhaust. It has no way of knowing where the extra oxygen came from. So keep that in mind when diagnosing oxygen sensor problems.
The lambda sensor is also grounded through the exhaust manifold. If rust and corrosion of the manifold gaskets and bolts is creating resistance, it may affect the sensor's output. To rule out a bad ground, use a digital volt meter to check for a voltage drop between the sensor shell and the engine block. More than 0.1v can cause a problem.
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