Chart C-1B Bank 1 Heated Oxygen Sensor Check

Chart C-1B:

Heated Oxygen Sensor Circuit:

CIRCUIT DESCRIPTION
The Powertrain Control Module (PCM) provides a 0.45 volt reference signal to the oxygen sensor on CKT 1670. When warm, a properly operating oxygen sensor will drive the 0.45 volt reference lower (below 0.45 volt) to indicate a lean mixture, and higher (above 0.45 volt) to indicate a rich mixture. The oxygen sensor signal voltage will toggle from rich to lean rapidly, at least one toggle every two seconds, if the PCM is in good control of the air/fuel mixture.
Powertrain Chart C-1B is designed to be used after the oxygen sensor circuit and PCM operation have been verified through the On-Board Diagnostic System Check and DTC(s) diagnosis. Testing and Inspection
Chart C-1B should identify oxygen sensors that are:

- Open-not able to drive the 0.45 volt reference signal high (rich) or low (lean).
OR
- Shorted-sensor output is fixed high (above 0.45 volt) or low (below 0.45 volt) due to contaminants or internal sensor faults.

CHART TEST DESCRIPTION
Number(s) below refer to circled number(s) on the diagnostic chart.

1. With the engine running warm coolant temperature above 82°C (180°F) and at fast idle, observe engine data parameter for Bank 1 Heated Oxygen Sensor (H02S) voltage, that should normally alternate between below 0.3 volt and above 0.6 volt.
2. While running the engine at a fast idle, observe the "Open/Closed Loop" status. If the PCM switches the system to "Closed Loop" operation, then the oxygen sensor is OK. If the PCM remains in "Open Loop" operation and the coolant temperature is above 82°C (180°F), then replace the oxygen sensor.
3. If the voltage remains between 0.30 and 0.60 for a minimum of 1 minute, replace the oxygen sensor and check for cause of oxygen sensor contamination.
4. If there is no voltage variation, there is intermittent terminal contact or the oxygen sensor is faulty.