Schematic Reference: Engine Controls Schematics

The heated oxygen sensor (HO2S) produces a voltage that varies between 100 mV and 900 mV. The powertrain control module (PCM) monitors this voltage and determines by the exhaust gas oxygen content whether the air/fuel mixture is rich or lean. When the voltage input at the PCM is about 100 mV the HO2S is indicating a lean air/fuel mixture. When the voltage input is about 900 mV the HO2S is indicating rich air/fuel mixture. The PCM constantly monitors the HO2S signal during closed loop operation and compensates for the rich or the lean condition by decreasing or increasing fuel injector pulse width. A DTC P0130 may set if the O2S 1 voltage remains excessively high or low for an extended period of time.

The O2S 1 output voltage stays between 0.40 volts and 0.55 volts.

OR

The O2S 1 output voltage is always less than 0.55 volts.

OR

The O2S 1 output voltage is always more than 0.40 volts.

A DTC P0130 is more likely to set during city driving. Avoid operating the vehicle on the highway when validating a DTC P0130.

Clear the DTCs. Road test the vehicle while monitoring the HO2S test in the MIL/System Status selection under System Information on the scan tool. When the HO2S test indicates complete with a YES status, check for a DTC P0130 under Last Test Failed. If there is no DTC P0130 indicated, the DTC is intermittent and the HO2S system diagnostic is indicating OK at this time.

The scan tool output control feature, Fuel Injector Modification, can be used at idle to check oxygen sensor performance. Increasing the Fuel Injector Modification Commanded State to 25% should cause the O2S 1 voltage to exceed 800 mv. Decreasing the Fuel Injector Modification Commanded State to -12% should cause the O2S 1 voltage to drop below 100 mv. An oxygen sensor that fails to respond accordingly may be faulty or contaminated. When performing Fuel Injector Modification with the scan tool, the Loop Status will remain OPEN LOOP and the Short Term FT will be fixed at 0% and 128 COUNTS.

Check for any of the following conditions:

An intermittent malfunction may be caused by a fault in the O2S 1 electrical circuit. Inspect the wiring harness and components for any of the following conditions:

Repair any electrical circuit faults that were found. Refer to Wiring Repairs in Wiring Systems.

The information included in the Freeze Frame data can be useful in determining the vehicle operating conditions when the DTC first set.

The numbers below refer to the step numbers in the Diagnostic Table.

1. The OBD System Check prompts the technician to complete some basic checks and store the freeze frame data on the scan tool if applicable. This creates an electronic copy of the data taken when the fault occurred. The information is then stored in the scan tool for later reference.

2. This step verifies whether the malfunction is presently occurring.

3. This step checks whether the malfunction that caused the DTC P0130 is still present. Operating the vehicle in check mode enhances the PCMs diagnostic capabilities. The O2S 1 diagnostic can be monitored on the scan tool under the MIL/System Status selection of System Information. When the HO2S test displays a YES status (indicating that the heated oxygen sensor system diagnostic is completed) check for a DTC P0130 in the Last Test Failed screen of the scan tool. If there is no DTC P0130 displayed the HO2S diagnostic has run and passed, indicating that no malfunction was present this time. DTCs MUST BE CLEARED in order to view the CURRENT STATUS of the system diagnostics being performed. Do not forget that the MIL/System Status tests only indicate that the test has run, not whether the test passed or failed. The Last Test Failed screen must be checked for related DTCs in order to determine the outcome of the diagnostic test involved. For additional information on check mode operation refer to Powertrain Control Module Diagnosis.

4. In this step the DMM is used as a low current voltage source taking the place of the HO2S. This step verifies whether the PCM is able to receive and process a signal from the O2S 1.