The DTC P0133 Heated Oxygen Sensor (HO2S) Slow Response Bank 1 Sensor 1 diagnostic monitors the switching rate of the bank 1 fuel control HO2S. The DTC  P0153 Heated Oxygen Sensor (HO2S) Slow Response Bank 2 Sensor 1 diagnostic monitors the switching rate of the bank 2 fuel control HO2S. The powertrain control module (PCM) continuously monitors the heated oxygen sensor (HO2S) activity. During the monitoring period the PCM counts the number of times that a rich-to-lean and lean-to-rich response is indicated. The PCM then combines these counts with the amount of time involved to complete the transitions. With this information, an average time for each transition can be determined. If the average response time is too slow, DTC P0133 or DTC P0153 will be set.

A lean-to-rich transition is indicated when the HO2S voltage changes from less than 300 mV to more than 600 mV. A rich-to-lean transition is indicated when the HO2S voltage changes from more than 600 mV to less than 300 mV. A HO2S that responds too slowly is likely to be faulty and should be replaced.

A DTC P0133 is more likely to set during city driving. Avoid operating the vehicle on the highway when validating a DTC P0131.

Check for any of the following conditions:

If a DTC P0133 or DTC P0153 is intermittent, driving the vehicle under the conditions outlined in the Inspection/Maintenance (I/M) section can verify whether the fault is present. Refer to Inspection/Maintenance Heated Oxygen Sensor/Oxygen Sensor System Set .

An intermittent malfunction may be caused by a fault in the mass air flow (MAF) sensor circuit. Inspect the wiring harness and components for an intermittent condition. Refer to Intermittent Conditions .

If the DTC P0133 or DTC P0153 cannot be duplicated, the information included in the Freeze Frame data can be useful in determining vehicle operating conditions when the DTC was first set.

The numbers below refer to the step numbers in the diagnostic table.

1. The Diagnostic System Check-Engine Controls 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 determines if the fault is present.

4. This step checks for an exhaust leak near the HO2S. Fresh air can enter the exhaust system through the exhaust leak and affect HO2S 1 performance.

7. This step checks whether the malfunction that caused the DTC P0133 or DTC P0153 is still present. Driving the vehicle under these conditions will verify whether the fault is present. After performing the scan tool clear DTC information function, the DTC P0133 or DTC P0153 diagnostic can be monitored on the scan tool under the Not Ran Since Code Cleared selection in the DTC Information menu. If DTC P0133 or DTC P0153 appears in the Not Ran Since Code Cleared list, the DTC diagnostic has not yet run. When DTC does not appear in the Not Ran Since Code Cleared list, the DTC diagnostic has run. If the MIL is NOT illuminated and there is no Pending DTC Status in DTC Information, the DTC diagnostic has passed. DTCs MUST be cleared in order to view the Current Status of the Not Ran Since Code Cleared list. DO NOT forget that the Not Ran Since Code Cleared list only indicates that the test has run, not whether the test passed or failed. The DTC Information screen must be checked for Current or Pending status, in order to determine the outcome of the diagnostic test involved.