Refer to
HO2S Sensors
.
Circuit Description
The powertrain control module (PCM) continuously monitors the heated oxygen sensor (HO2S) activity for 120 seconds. During the monitoring period the PCM counts the number of times that the a rich to lean and lean to rich response is indicated and adds the amount of time it took to complete all 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 malfunctioning and should be replaced.
Conditions for Setting the DTC
| • | No EGR, Transaxle, TP sensor, EVAP system, misfire, IAT sensor, MAP sensor, fuel trim, fuel injector circuit, ECT sensor, HO2S heater circuit sensor 1, or MAF sensor DTC(s) present |
| • | Engine has been running in Closed Loop fuel control for at least 2 minutes. |
| • | Engine speed is between 1000 RPM and 3000 RPM. |
| • | Engine Coolant Temperature greater than 75°C (167°F). |
| • | Mass Air Flow between 15 gm/s and 29 gm/s. |
| • | Vin 1 - H02S 1 lean to rich average transition response time during the sample period was longer than 75 milliseconds or rich to lean average transition response time during the sample period was longer than 100 milliseconds. |
| • | Vin K - H02S 1 lean to rich average transition response time during the sample period was longer than 139 milliseconds or rich to lean average transition response time during the sample period was longer than 107 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 Connections at PCM. Inspect harness connectors for backed out terminals, improper mating, broken locks, improperly formed or damaged terminals, and poor terminal to wire connection. |
| • | Damaged harnesss. 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 malfunction. 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
Number(s) below refer to the step number(s) 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 On-Board Diagnostic (OBD) System Check performed? | -- | ||||||||||
|
Important: If any DTCs are set (except P1133 or P1134), refer to those DTCs before proceeding with this diagnostic chart.
Does the scan tool indicate DTC P0133 failed this ignition? | -- | Refer to Diagnostic Aids | ||||||||||
Did the scan tool also indicate DTC P1133 or P1134 failed this ign? | -- | |||||||||||
4 |
Was a problem found? | -- | ||||||||||
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? | 450mV | ||||||||||
7 |
Does scan tool indicate voltage less than specified value? | 300mV | ||||||||||
8 | Replace the affected heated oxygen sensor(s). Refer to Heated Oxygen Sensor Replacement . Important: Check for HO2S contamination. Refer to
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.
Is action complete? | -- | -- | |||||||||
9 | Repair condition as necessary. Is action complete? | -- | -- | |||||||||
10 | Repair open HO2S 1 low signal circuit or grounded HO2S 1 high signal circuit. Refer to Heated Oxygen Sensor (O2S) Repair in Electrical Diagnosis. Is action complete? | -- | -- | |||||||||
11 | Repair open HO2S 1 high signal circuit or faulty PCM connections. Refer to Heated Oxygen Sensor (O2S) Repair in Electrical Diagnosis. Is action complete? | -- | -- | |||||||||
12 | Replace HO2S 1. Refer to Heated Oxygen Sensor Replacement . Is action complete? | -- | -- | |||||||||
13 |
Does the scan tool indicate DTC P0133 failed this ignition? | -- | System OK |
