Code P0133, Bank 1 Ho2S No. 1 Circuit Slow Response: Notes

PCM continuously monitors Heated Oxygen Sensor (HO2S) activity for 100 seconds. During the monitoring, the PCM counts the number of times the HO2S switches from rich to lean and from lean to rich, and adds the amount of time required to complete all switches. Thus, an average time for all switches can be determined. If the average time to switch is too slow, Code P0133 will set. A HO2S that switches too slowly is most likely defective and should be replaced. Code P0133 will set when the following conditions are present.

Engine is started.
Intake air and engine coolant temperatures are less than 122°F (50°C).
Intake air and engine coolant temperatures are within 11°F (6°C) of one another at start-up.
TP sensor angle is between 2 and 10 percent for 100 seconds.
Engine is operating in closed loop mode.
Codes 14, 15, 18, 21, 22, 24, 26, 29, 33, 34, 36, 43, 47, 48, 50, 51, 53, 55, P0116, P0117, P0118, P0171, P0172, P0174, P0175, P1114 and P1115 are not set.
All conditions are met, and the average time for the HO2S to switch from lean to rich is longer than .1 second, or the average time for the HO2S to switch from rich to lean is longer than .1 second.

A lean to rich switch is determined when the HO2S voltage changes from less than .3 volt to greater than .6 volt. A rich to lean switch is determined when the HO2S voltage changes from greater than .6 volt to less than .3 volt. Code P0133 will only fail on a cold start with ECT and IAT less than 122°F (50°C), and within 11°F (6°C) at start-up. If a condition for Code P0133 is present and ECT is greater than 122°F (50°C), PCM will not run Code P0133 test.

Code P0133 will be stored in PCM memory, but will not illuminate Malfunction Indicator Light (MIL). A failed last test code will clear when the fault conditions no longer exist. A history code will clear after 40 ignition cycles without a fault, when the battery has been disconnected for 30 seconds, or when the code clearing feature on the Tech 1 is used.

NOTE: Test numbers refer to numbers on diagnostic chart.

Code P0135 (HO2S HEATER CIRCUIT MALFUNCTION) can cause Code P0133 to set. Repair heater circuit before proceeding with this chart.
An exhaust leak 6-12" away from HO2S in either direction can cause Code P0133 to set. Thoroughly inspect exhaust system for leaks.
An HO2S that is contaminated by oil will be Dark Brown in appearance. An HO2S that is contaminated by coolant will be Whitish Green in appearance.
Certain RTV silicone gasket materials release vapors that can contaminate the HO2S. Silicone in the fuel can cause silica contamination. If sensor appears to be contaminated by silica, and all other sealants are non-silica base, advise customer to select a different fuel company. A missing fuel filler restrictor indicates leaded fuel may have been used.