Test Description

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

2: This step determines if the condition is present. This test may take 5-10 minutes for the diagnostic to run.
4: An exhaust leak 6-12 inches away from the HO2S can cause a DTC to set.
5: Certain RTV silicone gasket materials release vapors that can contaminate the HO2S. Silicone in the fuel can also cause silicone contamination. If the sensors appear contaminated by silicone, and if all the silicone sealant is a non-silicone base, advise the customer to try a different fuel company. A missing fuel filler restrictor indicates that the customer may have used leaded fuel.

DTC P0133

Step	Action	Values	Yes	No
Schematic Reference: Engine Controls Schematics Connector End View Reference: Engine Control Module (ECM) Connector End Views or Engine Controls Connector End Views
1	Did you perform the Diagnostic System Check - Engine Controls?	-	Go to Step 2	Go to Diagnostic System Check - Engine Controls
2	IMPORTANT: If any DTCs are set, except P0133, refer to those DTCs before proceeding with this diagnostic table. Allow the engine to reach the normal operating temperature. Operate the vehicle within the parameters specified in Conditions for Running the DTC. Observe the diagnostic trouble code (DTC) information with a scan tool. Did DTC P0133 fail this ignition cycle?	-	Go to Step 4	Go to Step 3
3	Observe the Freeze Frame/Failure Records for this DTC. Turn OFF the ignition for 30 seconds. Start the engine. Operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records. Did the DTC fail this ignition?	-	Go to Step 4	Go to Intermittent Conditions
4	Inspect for an exhaust leak near the HO2S. Refer to Symptoms - Engine Exhaust in Engine Exhaust. After you inspect the exhaust system, return to this diagnostic. Did you find and correct the condition?	-	Go to Step 7	Go to Step 5
5	Inspect or test for the following conditions: The HO2S is securely installed. Inspect for corrosion on the HO2S terminals. Inspect the terminal tension at the HO2S and at the ECM. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Inspect the HO2S wiring for damage. Refer to Wiring Repairs in Wiring Systems. Fuel that is contaminated - Refer to Alcohol/Contaminants-in-Fuel Diagnosis (W/O Special Tool) or Alcohol/Contaminants-in-Fuel Diagnosis (W/Special Tool) . Inspect for the correct RTV sealant. Inspect for engine oil consumption. Refer to Oil Leak Diagnosis in Engine Mechanical - 1.6L (L91). Inspect for engine coolant consumption. Refer to Loss of Coolant in Engine Cooling. Did you find and correct the condition?	-	Go to Step 7	Go to Step 6
6	Replace the HO2S 1. Refer to Heated Oxygen Sensor Replacement - Position 1 . Did you complete the replacement?	-	Go to Step 7	-
7	Clear the DTCs with a scan tool. Turn OFF the ignition for 30 seconds. Start the engine. Operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records. Did the DTC fail this ignition?	-	Go to Step 2	Go to Step 8
8	Observe the Capture Info with a scan tool. Are there any DTCs that have not been diagnosed?	-	Go to Diagnostic Trouble Code (DTC) List	System OK