Circuit Description
The PCM continuously monitors the Heated Oxygen Sensor (HO2S) activity for 100 seconds. During the monitoring period the PCM averages the amount of time of rich to lean and lean to rich transitions. With this information, an average time for each transition can be determined. If the average response time is too slow, a DTC P0133 will be set.
A lean to rich transition is indicated when the HO2S voltage changes from less than 300 mV to greater than 600 mV. A rich to lean transition is indicated when the HO2S voltage changes from more than 600 mV to less than 300 mV. An HO2S that responds too slowly is likely to be faulty and should be replaced.
Conditions for Setting the DTC
| • | No active misfire, fuel injector circuit, TP sensor, EVAP, IAT sensor, MAP sensor, Fuel trim, EGR, ECT sensor, MAF sensor or CKP sensor DTCs present. |
| • | Engine has been running in Closed Loop for at least 1 minute. |
| • | Engine speed is between 1000 RPM and 3000 RPM. |
| • | Engine Coolant Temperature greater than 50°C (122°F). |
| • | Mass Air Flow between 10 gm/s and 30 gm/s. |
| • | H02S 1 lean to rich average transition response time was longer than 153 milliseconds. |
| • | H02S 1 rich to lean average transition response time was longer than 148 milliseconds. |
Action Taken When the DTC Sets
| • | The PCM will illuminate the malfunction indicator lamp (MIL) during the second consecutive trip in which the diagnostic test has been run and failed. |
| • | 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
Check for the following conditions:
| • | Poor connection at PCM. Inspect harness connectors for backed out terminals, improper mating, broken locks, improperly formed or damaged terminals, and poor terminal to wire connection. Refer to Intermittents and Poor Connections Diagnosis Repairing Connector Terminals and Connector Repairs . |
| • | Damaged harness. Inspect the wiring harness for damage. If the harness appears to be OK, observe the H02S 1 display on the scan tool while moving connectors and wiring harnesses related to the sensor. A change in the display will indicate the location of the fault. Refer to Wiring Repairs . |
| • | Check for HO2S contamination. Refer to notice
Notice: Contamination of the oxygen sensor can result from the use of an inappropriate RTV sealant (not oxygen sensor safe) or excessive engine coolant or oil consumption. Remove the HO2S and visually inspect the portion of the sensor exposed to the exhaust stream in order to check for contamination. If contaminated, the portion of the sensor exposed to the exhaust stream will have a white powdery coating. Silicon contamination causes a high but false HO2S signal voltage (rich exhaust indication). The control module will then reduce the amount of fuel delivered to the engine, causing a severe driveability problem. Eliminate the source of contamination before replacing the oxygen sensor. . |
If DTC P0133 cannot be duplicated, 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
The numbers below refer to the step numbers on the Diagnostic Table:
-
Verifies that the fault is currently present.
-
HO2S transition time, ratio, and switching DTCs set for multiple sensors indicate probable contamination. Before replacing the sensors, isolate and correct the source of the contamination to avoid damaging the replacement sensors.
Step | Action | Value(s) | Yes | No | ||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
1 | Was the Powertrain OBD System Check performed? | -- | ||||||||||
If any DTCs are set, (P1133, P1134), refer to those DTCs before proceeding with this diagnostic chart.
Does scan tool indicate DTC P0133 failed this ignition? | -- | Go to Diagnostic Aids | ||||||||||
Did the scan tool also indicate DTC P1133, P1134, failed this ignition? | -- | |||||||||||
4 |
Was an exhaust leak isolated? | -- | ||||||||||
5 | Visually/physically inspect the following items:
Was a problem found in any of the above areas? | -- | ||||||||||
6 |
Does the scan tool indicate voltage near the specified value? | 450 mV | ||||||||||
7 |
Does scan tool indicate voltage below specified value? | 300 mV | ||||||||||
8 | Replace affected Heated Oxygen Sensors. Refer to Heated Oxygen Sensor (HO2S) Replacement . Important: : Before replacing sensors, the cause of the contamination must be determined
and corrected.
Is the action complete? | -- | -- | |||||||||
9 | Repair condition as necessary. Refer to Wiring Repairs . Is the action complete? | -- | -- | |||||||||
10 | Repair open HO2S 1 low signal circuit or grounded HO2S 1 high signal circuit. Refer to Wiring Repairs . Is the action complete? | -- | -- | |||||||||
11 | Repair open HO2S 1 high signal circuit or faulty PCM connections. Refer to Wiring Repairs . Is the action complete? | -- | -- | |||||||||
12 | Replace HO2S 1. Refer to Heated Oxygen Sensor (HO2S) Replacement . Is the action complete? | -- | -- | |||||||||
13 |
Does scan tool indicate DTC P0133 failed this ignition? | -- | System OK |
