DESCRIPTION
| CAUTION | 1986-90 Jeep vehicles are equipped with either Zirconia type or Titania type oxygen sensors. This article includes component testing procedures for Titania type sensors. Ensure sensor type is identified correctly. They are not interchangeable. |
Bendix systems use a Renix controller. Renix Engine Control Unit (ECU) can be identified by connectors. (Scheme 123) Oxygen (O2) sensors used on Renix-controlled 1986-90 2.5L and 1987-90 4.0L engines are Titania O2 sensors. Instead of being a voltage generating O2 sensor (Zirconia type), Titania O2 sensors vary resistance in relation to oxygen content in exhaust. All Titania O2 sensors are 3-wire, but not all 3-wire O2 sensors are Titania O2 sensors. Titania O2 sensors are not vented to the atmosphere.
Scheme 123
OPERATION
A 5-volt reference voltage signal is sent through a fixed resistor internal to Renix ECU. (Scheme 124) The output from the resistor is monitored by ECU. The reference voltage is connected to input of O2 sensor. Unlike zirconia O2 sensors, when oxygen content is low (rich mixture), voltage signal is less than 2.5 volts. When oxygen content is high (lean mixture), voltage signal is more than 2.5 volts.
Titania O2 sensors are heated. Voltage is supplied to heating element by a PCM-controlled relay. Titania O2 sensor heating element resistance is 5-7 ohms. Titania O2 sensor output should be similar (response time, cross counts), except for voltage. Instead of 0-1 volt, low voltage equals lean (Zirconia), Titania O2 sensor voltages are 1-5 volts, high voltage equals lean.
