02 sensor 1989 Jeep 4.0L
I have been having problems getting the EFIE device that I am testing for Gary "Chemlec". The device tests and worked properly on the bench. However on the Jeep I keep getting high voltage readings . the OBC is sending 3.85 volts to the sensor. Anyway I found this info on internet that explains my problem:
02 Sensor on 1989 Jeep 4.0L.
In case you're not aware of it, the oxygen sensors used on 1987 to 1990 Jeep 4.0L engines, as well as the 3.0L Eagle Premier engines, are not voltage-generating sensors. These are titania-style sensors. As with zirconia-style oxygen sensors, by measuring the amount of oxygen present in the exhaust, the ECU can make the adjustments necessary to the pulse width of the injectors. The resistance element in the oxygen sensor is a titania semiconductor (see Fig. 2). A 5-volt reference is applied to a fixed resistor (inside the ECU) that is wired in series with the sensor. The ECU monitors the voltage drop across this resistor to determine if the mixture is rich or lean. Because of this characteristic, poor connections can easily cause false readings in the system. Changes in the voltage signal from the oxygen sensor serve as air/fuel indicators. The changes occur because this style sensor acts as a variable resistor. When the oxygen content is low (rich mixture), the voltage signal will be less than 2.5 volts. With a lean mixture (high oxygen content), the voltage signal will be more than 2.5 volts. This style sensor is a heated sensor. The heater is a 12-volt resistance-style element. Power is supplied from an oxygen sensor heater relay, which is controlled by the ECU. The relay is a normally closed type. When the ECU determines that the engine is up to operating temperature and there is enough exhaust flow to keep the sensor hot, the ECU supplies a ground to a relay coil, opening the heater circuit to the sensor. The resistance value is approximately 5-7 ohms. Remember, this is for the heating element only, not the titania element. The oxygen sensors on these engines are a very big input for fuel control. If the sensor gets slow, or worse yet, gets stuck, you will experience major driveability problems - anything from surging, poor idle to black smoke from the exhaust. As you can see, it is more than a trim device. Testing the sensor is like testing the regular sensor you've been used to, except everything you learned about oxygen sensors is backward! You can test the sensor by backprobing (or if you're lucky, you'll have a scan tool that will work on the system). The voltage should be fluctuating from 0-5 volts when the system is in closed loop. All other rules about oxygen sensors apply, such as response time, testing procedures and safeguards. Remember that if you artificially enrich the mixture, the voltage should drop low (less than 2.5 volts), and if you give the engine a big vacuum leak, the voltage should go high (more than 2.5 volts) - the high and low voltages are just the opposite of zirconia-style sensors.
Recon I can still use my device if I readjust the low and high presets? The device I am using is a improved version (but basically the same) of this device. http://better-mileage.com/memberadx.html