Circuit Description
The PCM monitors the Heated Oxygen Sensor (HO2S) activity for 100 seconds. 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 thresholds. If the PCM determines that the HO2S did not switch enough times, DTC P1133 will be set.
A lean to rich switch is determined when the HO2S voltage changes from less than 300 mV to greater than 600 mV. A rich to lean switch is determined when the HO2S voltage changes from more than 600 mV to less than 300 mV.
Conditions for Running the DTC
| • | No active MAF, TP, IAT, MAP, ECT, EGR sensor, injector circuit, EVAP, fuel trim, or HO2S heater DTCs. |
| • | Above conditions present for a 100 second monitoring period after closed loop. |
| • | Mass Air Flow is between 10 and 30 g/s. |
| • | ECT is greater than 50°C (122°F). |
| • | Engine speed is between 1000 and 3000 RPM. |
Conditions for Setting the DTC
| • | The PCM monitors fewer than 40 rich to lean and 40 lean to rich switches for HO2S 1. |
| • | The condition is present for a 100 second monitoring period. |
Action Taken When the DTC Sets
| • | The PCM will illuminate the malfunction indicator lamp (MIL) during the second consecuitive trip in which the diagnostic has been run and failed. |
| • | If equipped with traction control, the PCM will command the EBTCM via the serial data circuit to turn OFF traction control, and the EBTCM will illuminate the TRACTION OFF lamp. |
| • | The PCM will store conditions which were present when the DTC set as Freeze Frame and Failure Records data. |
Conditions for Clearing the MIL/DTC
| • | The PCM will turn OFF the MIL during the third consecutive trip in which the diagnostic has been run and passed. |
| • | The History DTC will clear after 40 consecutive warm-up cycles have occurred without a malfunction. |
| • | The DTC can be cleared by using the scan tool. |
Diagnostic Aids
A malfunction in the HO2S heater ignition feed or ground circuit may cause a DTC P1133 to set. Check HO2S heater circuitry for intermittent faults or poor connections. If connections and wiring are OK and DTC P1133 continues to set, replace the HO2S 1.
Refer to Testing for Continuity , Intermittents and Poor Connections Diagnosis , Repairing Connector Terminals , and Connector Repairs in Wiring Systems.
Reviewing the Fail Records vehicle mileage since the diagnostic test last failed may help determine how often the condition that caused the DTC to be set occurs. This may assist in diagnosing the condition.
Test Description
Number(s) below refer to the step number(s) on the Diagnostic Table:
-
This step Tests for conditions which may cause the heated oxygen sensor to appear faulty. Correct any of the described conditions if present.
-
Before replacing the HO2S, Test for silicon contamination.
Step | Action | Value(s) | Yes | No | ||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
1 | Was the Powertrain OBD System Check performed? | -- | ||||||||||
2 |
Important: : If any DTCs are set (except P1133 or P1134), go to those DTCs before proceeding with this diagnostic table.
Note the test result, does the scan tool indicate DTC failed this ignition? | -- | Go to Diagnostic Aids | |||||||||
3 |
Was a problem found? | -- | ||||||||||
Visually/physically inspect the following items:
Was a problem found in any of the above areas? | -- | |||||||||||
5 |
Does the scan tool indicate voltage near the specified value? | 450mV | ||||||||||
6 |
Does the scan tool indicate voltage less than the specified value? | 300mV | ||||||||||
Replace the affected Heated Oxygen Sensor(s). Refer to Heated Oxygen Sensor (HO2S) Replacement . Is the action complete? | -- | -- | ||||||||||
8 | Repair the condition as necessary. Refer to Intermittents and Poor Connections Diagnosis Repairing Connector Terminals and Connector Repairs in Wiring Systems. Is the action complete? | -- | -- | |||||||||
9 | Repair open HO2S 1 low signal circuit or grounded HO2S 1 high signal circuit. Refer to Heated Oxygen Sensor (HO2S) Replacement . Is the action complete? | -- | -- | |||||||||
10 | Repair open HO2S 1 high signal circuit or faulty PCM connections. Refer to Heated Oxygen Sensor (HO2S) Replacement . Is the action complete? | |||||||||||
11 |
Note the test result, does the scan tool indicate DTC failed this ignition? | -- | System OK |
