For 1990-2009 cars
Engine Controls Components
HO2S Sensors
OBD II Symbol Description Notice
Handling ESD Sensitive Parts Notice

### 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 50°C (122°F).

• | Mass Air Flow between 15 gm/s and 30 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 110 milliseconds.

• | Vin K - H02S 1 lean to rich average transition response time during the sample period was longer than 155 milliseconds or rich to lean average transition response time during the sample period was longer than 115 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:

1. Verifies that the malfunction is currently present.

2. 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.

#### DTC P0133 - HO2S Slow Response Sensor 1

Step | Action | Value(s) | Yes | No
--- | --- | --- | --- | ---
1 | Was the Powertrain On-Board Diagnostic (OBD) System Check performed? | -- | Go to Step 2 | Go to the Powertrain On Board Diagnostic (OBD) System Check
2 | Important: If any DTCs are set, except P1133 or P1134, refer to those DTCs before proceeding with this diagnostic table.

1. Engine idling at operating temperature.
2. Operate the vehicle within the parameters specified under DTC P0133 Conditions For Setting The DTC criteria included in Diagnostic Support.
3. Using a scan tool, monitor Specific DTC info for DTC P0133 until the DTC P0133 test runs.

Des the scan tool indicate DTC P0133 failed this ignition?

--

Go to Step 3

Go to Diagnostic Aids

3 | Did the scan tool also indicate DTC P1133 or P1134 failed this ign? | -- | Go to Step 8 | Go to Step 4
4 |

1. Perform the Exhaust System Leak Test. Refer to Exhaust System . After the Exhaust System Leak Test has been performed, return to this diagnostic.
2. If an exhaust leak is found, repair as necessary.

Was a problem found?

--

Go to Step 13

Go to Step 5

5 | Visually/physically inspect the following items:

• | Ensure that the HO2S 1 is securely installed.

• | Check for corrosion on terminals.

• | Check terminal tension (at HO2S 1 and at the PCM).

• | Check for damaged wiring.

Was a problem found in any of the above areas?

--

Go to Step 9

Go to Step 6

6 |

1. Disconnect HO2S 1 and jumper the HO2S low signal circuit to ground.
2. Using a scan tool, monitor HO2S 1 voltage.

Does the scan tool indicate voltage near the specified value?

450 mV

Go to Step 7

Go to Step 10

7 |

1. Jumper the HO2S 1 high and low signal circuits to ground.
2. Using a scan tool, monitor HO2S 1 voltage.

Does the scan tool indicate voltage less than specified value?

300 mV

Go to Step 12

Go to Step 1

8 | Notice: Correct the source of the oxygen sensor contamination before replacing the sensor in order to prevent future contamination. Typical contamination sources include the following:

• | Fuel contamination

• | Use of improper RTV sealant

• | Engine oil or engine coolant consumption

Replace the affected Heated Oxygen Sensor(s).

• | Fuel contamination

• | Use of improper RTV sealant.

• | Engine oil/coolant consumption.

Is action complete?

--

Go to Step 13

--

9 | Repair the condition as necessary. Is action complete? | -- | Go to Step 13 | --
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? | -- | Go to Step 13 | --
11 | Repair open HO2S 1 high signal circuit or malfunctioning PCM connections. Refer to Heated Oxygen Sensor (O2S) Repair in Electrical Diagnosis. Is action complete? | -- | Go to Step 13 | --
12 | Replace HO2S 1. Refer to Heated Oxygen Sensor Replacement . Is action complete? | -- | Go to Step 13 | --
13 |

1. Review and record scan tool Fail Records data.
2. Clear DTCs
3. Operate the vehicle within Fail Records conditions as noted.
4. Using a scan tool, monitor Specific info for DTC P0133 until the DTC P0133 test runs.

Does the scan tool indicate DTC P0133 failed this ignition?

--

Go to Step 2

System OK