For 1990-2009 cars

Refer to

#### Oxygen Sensors

Engine Controls Components
Information Sensors
IAC Valve, Generator, TR, Oil, and Coolant Switches
EVAP and EGR Controls
OBD II Symbol Description Notice
Handling ESD Sensitive Parts Notice
schematic.

### Circuit Description

The PCM continuously monitors the Heated Oxygen Sensor (HO2S) activity for 100 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 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 DTC(s) present.

• | Engine has been running in Closed Loop for at least 2 minutes.

• | Engine speed is between 1000 RPM and 3000 RPM.

• | Engine Coolant Temperature greater than 85°C (185°F).

• | Mass Air Flow between 15 gm/s and 28 gm/s.

• | H02S 1 lean to rich or rich to lean average transition response time was longer than 54 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.

• | 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.

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.

1. Verifies that the fault 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 Check performed? | -- | Go to Step 2 | Go to Powertrain On Board Diagnostic (OBD) System Check
2 |

Important: If any DTCs are set, (P1133, P1134), refer to those DTCs before proceeding with this diagnostic chart.

1. Engine idling at operating temperature.
2. Operate vehicle within parameters specified under 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.

Does 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, P1134, failed this ignition? | -- | Go to Step 8 | Go to Step 4
4 |

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

Was an exhaust leak isolated?

--

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 HO2S low (PCM side) 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 HO2S 1 high and low (PCM side) signal circuits to ground.
2. Using a scan tool, monitor HO2S 1 voltage.

Does scan tool indicate voltage below specified value?

300 mV

Go to Step 12

Go to Step 11

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 affected Heated Oxygen Sensors.

Is action complete?

--

Go to Step 13

--

9 | Repair 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 Repair Procedures Electrical Diagnosis Section 8A. Is action complete? | -- | Go to Step 13 | --
11 | Repair open HO2S 1 high signal circuit or faulty PCM connections. Refer to Heated Oxygen Sensor (O2S) Repair in Repair Procedures Electrical Diagnosis Section 8A. Is action complete? | -- | Go to Step 13 | --
12 | Replace HO2S 1. Is action complete? | -- | Go to Step 13 | --
13 |

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

Does scan tool indicate DTC P0133 failed this ignition?

--

Go to Step 2

Repair complete