With Standard Emissions

CODE 13 OXYGEN SENSOR CIRCUIT

O2S Circuit Checkout:

Oxygen Sensor Circuit:

CIRCUIT DESCRIPTION
The Oxygen Sensor (02S) produces a varying voltage after the sensor is hot, above 360°C (680°F). This voltage varies from 0 to 900 mV (0.9 volts). The signal will vary depending on the exhaust gas oxygen content. After the sensor is hot, if the voltage stays above 450 mV for more than 10 seconds, this indicates a rich condition. If voltage remains below 450 mV for 10 seconds, a lean condition is indicated.

The 02S acts like an "open circuit" and produces no voltage when below 360°C (680°F). An open sensor circuit causes the engine to operate in an "OPEN LOOP" operation.

TEST DESCRIPTION
Numbers below refer to circled numbers on the diagnostic chart.

1. O2S output voltage, at this step, should be fluctuating between 0-1 volt.
2. When the vacuum hose is removed from the Manifold Absolute Pressure (MAP) sensor, its output voltage will increase, and the Engine Control Module (ECM) should interpret this as a high engine load. The ECM should increase the fuel injector pulse width, causing a rich A/F mixture. This should cause the O2S sensor to generate a high output voltage, usually more than 0.9 volt (900 mV).

DIAGNOSTIC AIDS
Normal voltage varies between 0 mV and 900 mV.

A loose or intermittent oxygen sensor ground circuit could cause a Diagnostic Trouble Code (DTC) 13. The grounding point at the engine is located on the rear of the intake manifold, on the lower right edge.