P1133

DTC P1133 O2 Sensor Insufficient Switching (Bank 1 Sensor 1)




Circuit Description
The powertrain control module (PCM) monitors the heated oxygen sensor (HO2S) activity for 90 seconds after "Closed Loop" has been enabled. During this test period the PCM counts the number of times that the HO2S signal voltage crosses the rich-to-lean and lean-to-rich threshold. If the PCM determines that the HO2S did not switch enough times, Diagnostic Trouble Code P1133 will be set.

A lean-to-rich switch is determined when the HO2S voltage changes above and below 450 mV. DTC P1133 is a type B code.

Conditions for Setting the DTC
- Engine coolant temperature (ECT) is above 60 °C (140 °F).
- Engine is operating in "Closed Loop".
- The engine has been running at least two minutes.
- Canister purge duty cycle is greater than 2 %.
- Calculated air flow between 17 and 32 grams/sec.
- Engine speed is between 1500 RPM and 3500 RPM.
- Above conditions are present for 1 second.
- 90 seconds after "Closed Loop" and has been achieved, the PCM monitors the oxygen sensor as it switches above and below 450 mV. If fewer than 12 rich-to-lean and 12 lean-to-rich switches are detected, Diagnostic Trouble Code P1133 will be set.

Action Taken When the DTC Sets
- The PCM will illuminate the malfunction indicator lamp (MIL) after the second consecutive trip in which the fault is detected.
- "Open Loop" fuel control will be in effect.
- The PCM will store conditions which were present when the Diagnostic Trouble Code was set as Freeze Frame and in the Failure Records data.

Conditions for Clearing the MIL/DTC
- The PCM will turn the MIL OFF on the third consecutive trip cycle during which the diagnostic has been run and the fault condition is no longer present.
- A history Diagnostic Trouble Code P1133 will clear after 40 consecutive warm-up cycles have occurred without a fault.
- Diagnostic Trouble Code P1133 can be cleared by using the Scan Tool's "Clear Info" function.

Diagnostic Aids
A malfunction in the HO2S heater ignition feed or ground circuit may cause a Diagnostic Trouble Code P1133 to set. Check HO2S heater circuitry for intermittent faults or poor connections. If connections and wiring are OK and Diagnostic Trouble Code P1133 continues to set, replace the Bank 1 HO2S 1.

Reviewing the Failure Records vehicle mileage since the diagnostic test last failed may help to determine how often the condition that caused the Diagnostic Trouble Code to be set occurs. This may assist in diagnosing the condition.

Steps 1 - 2:

Steps 3 - 6:

Steps 7 - 11:

Steps 12:

Test Description
Number(s) below refer to the step number(s) on the Diagnostic Chart:
3. A condition that affects other heated oxygen sensors indicates probable contamination. To avoid damaging the replacement sensors, correct the condition which caused the contamination before replacing the affected sensors.
5. This step checks for conditions which may cause the heated oxygen sensor to appear faulty. Correct any of the described conditions if present.
11. To avoid damaging replacement sensors, correct the condition which caused the contamination before replacing the affected sensors.