Powertrain Controls - ECM/PCM

Diagnostic Chart:

Wiring Diagram:

RICH OXYGEN SENSOR SIGNAL
The oxygen sensor (O2S) consists of a zirconia electrolyte between two platinum plates. When the sensor reaches approximately 318°C (600°F) it becomes an electrical source that responds to the oxygen content in the exhaust. The PCM produces a bias voltage of approximately 450 millivolts on the oxygen sensor circuit. When the sensor is cold its internal resistance is extremely high, therefore, the PCM recognizes the bias as an open circuit. As the sensor warms up, the internal resistance decreases. When the sensor reaches approximately 318°C (600°F), it starts producing a voltage based on the oxygen content in the exhaust stream. This voltage is used by the PCM to determine a rich or lean oxygen sensor signal and adjusts the fuel mixture accordingly.

DTC PARAMETERS

DTC 45 will set if:
^ The system is in closed loop mode.
^ TP sensor in a <2 and >20% range.
^ Oxygen sensor is greater than 750 mV for 30 seconds.
^ Diagnostic trouble codes 33 -34 are not present.

DIAGNOSTIC AIDS
When attempting to diagnose an intermittent problem use the Scan tool[1] to review supplemental diagnostic information. The supplemental data can be used to duplicate a problem.

Intermittents or opens suspected to be at the connector can be detected by using Diagnostic Service Probe. Voltage can be read on both wires without disconnecting any connectors.

POSSIBLE CAUSES:
If system is commanding lean, the oxygen sensor signal is around 900 mV and short term fuel trim (integrator) is in the 60's, the system is nearing or at maximum correction. Check for fuel leaking into cylinders or manifold.

^ Fuel pressure high
^ Leaking injector
^ EVAP canister purge
^ Oxygen sensor contamination
^ EGR valve
^ Engine oil contamination
^ Shorted injector
^ Vacuum leak to map sensor
^ Leaking pressure regulator

[1] Select Malfunction History from Scan tool Engine Control (EC) menu.