I had the following error codes

P1133 - HO2S Insufficient Switching Bank 1 Sensor 1
P0133 - O2 Sensor Circuit Slow Response Bank 1 Sensor 1
P0130 - O2 Sensor Circuit Bank 1 Sensor 1
P0442 - EVAP System Leak Detected (small leak)
P0455 - EVAP System Leak Detected (large leak)

I went ahead an replaced my upstream O2 sensor. I immeditaly reset the memory and drove my car for 15 minutes. Now I have this code pending

P1133 - HO2S Insufficient Switching Bank 1 Sensor 1

I don't think having replacing my O2 sesnor fixed my problem. What is the next logical step?

I have a Saturn Ion 2003.


1 Answer 1


Check for an exhaust leak before or right after the o2 sensor, have someone use a rag and plug the exhaust while you listen. Or smoke test the exhaust system. Also check for vacuum leaks or any other lean/rich condition that would drive the o2 sensor in one direction or another.

If you don't find an exhaust/vacuum leak you'll want to back probe the sensor signal wires and monitor the voltage with a scope.

Conditions For Setting DTC

ECM detects that the HO2S 1 Lean/Rich average transition time is more than 200 milliseconds or the Rich/Lean average transition time is more than 130 milliseconds

You should also check for a short to power or ground on the signal wires and check the bias voltage with the sensor unplugged, bias voltage should be 450mV.

Also note that brand can be important in some cases. OE is almost always the way to go. I believe NGK and Denso are two OE suppliers for GM o2 sensors.

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.