For 1990-2009 cars

### Circuit Description

Heated oxygen sensors (HO2S) are used for fuel control and post catalyst monitoring. Each HO2S compares the oxygen content of the surrounding air with the oxygen content of the exhaust stream. When the vehicle is first started the powertrain control module (PCM) operates in an Open Loop mode, ignoring the HO2S signal voltage when calculating the air-to-fuel ratio. The PCM supplies the HO2S with a reference, or bias, voltage of about 450 mV. The HO2S generates a voltage within a range of 0-1,000 mV that fluctuates above and below bias voltage once in Closed Loop. A high HO2S voltage output indicates a rich fuel mixture. A low HO2S voltage output indicates a lean mixture. Heating elements inside the HO2S minimize the time required for the sensors to reach operating temperature, and provide an accurate voltage signal. This DTC will set if the HO2S 1 voltage average response time is too slow.

Each HO2S 1 has the following circuits:

• | HO2S 1 high signal

• | HO2S 1 low reference

• | HO2S 1 heater ignition 1 voltage

• | HO2S 1 heater low control

• | Low reference loop

### Conditions for Running the DTC

• | DTCs P0101, P0102, P0103, P0107, P0108, P0112, P0113, P0116, P0117, P0118, P0121, P0122, P0123, P0125, P0128, P0201, P0202, P0203, P0204, P0205, P0206, P0410, P0440, P0442, P0443, P0446, P0449, or P1441 are not set.

• | The vehicle is not in Park or Neutral.

• | The engine has been running for at least 4 minutes.

• | The mass air flow (MAF) is between 8-35 g/s.

• | The engine speed is between 550-3,000 RPM.

• | The throttle angle is between 3-35 percent.

• | The system voltage is between 9-18 volts.

• | The engine coolant temperature (ECT) is more than 70°C (158°F).

### Conditions for Setting the DTC

The DTC will set if either of the following conditions are present :

• | The HO2S 1 rich-to-lean transition time takes longer than 105 milliseconds

• | The HO2S 1 lean-to-rich transition time takes longer than 95 milliseconds

### Action Taken When the DTC Sets

The PCM illuminates the malfunction indicator lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.

The PCM records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the PCM stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the PCM records the operating conditions at the time of the failure. The PCM writes the operating conditions to the Freeze Frame and updates the Failure Records.

### Conditions for Clearing the MIL/DTC

• | The PCM turns OFF the MIL lamp after 3 consecutive ignition cycles that the diagnostic runs and passes.

• | A current, DTC last test fails, clears when the diagnostic runs and passes.

• | A DTC stored in history clears after 40 warm-up cycles, if no failures are reported by this or any other emission related diagnostic.

• | A scan tool can be used to clear the DTC.

### Test Description

The numbers below refer to the step numbers on the diagnostic table.

1. The HO2S 1 voltage may default to the bias voltage. The DTC should be cleared and the Freeze Frame/Failure Records data recorded before proceeding. A normally functioning HO2S 1 voltage signal will fluctuate above and below the bias voltage amount.

2. A voltage reading other than the specified amount in this step indicates an open circuit condition in the high signal circuit or the PCM.

3. This step checks the HO2S 1 signal circuits from the HO2S connector and the PCM connectors, including the low reference loop between the PCM connectors.

4. This step checks for correct HO2S 1 heater circuit operation up to the HO2S connector. The heater low control is controlled by the PCM. The engine must be running to enable the HO2S heater.

5. The conditions listed in the table may contribute to the failure of the HO2S. The conditions listed apply only to this type of failure.

Step | Action | Values | Yes | No
--- | --- | --- | --- | ---
Schematic Reference: Engine Controls Schematics
1 | Did you perform the Diagnostic System Check-Engine Controls? | -- | Go to Step 2 | Go to Diagnostic System Check - Engine Controls
2 |

1. Allow the engine to idle at operating temperature.
2. Observe the HO2S 1 voltage parameter with a scan tool.
3. Clear the DTC and record the Freeze/Frame Failure Records data if the HO2S 1 voltage is fixed at bias voltage.

Does the HO2S 1 voltage fluctuate rapidly above and below the specified value?

350-550 mV

Go to Step 3

Go to Step 4

3 |

1. Observe the Freeze Frame/Failure Records data for this DTC.
2. Turn OFF the ignition for 30 seconds.
3. Start the engine.
4. Operate the vehicle within the Conditions for Running the DTC as specified in the supporting text or as close to the Freeze Frame/Failure Records data that you observed.

Does the DTC fail this ignition?

--

Go to Step 4

Go to Intermittent Conditions

4 |

1. Turn OFF the ignition.
2. Disconnect the HO2S 1 connector.
3. Turn ON the ignition, with the engine OFF.
4. Measure the voltage from the high signal circuit of the HO2S 1 harness connector, on the engine side, to a good ground with a DMM.

Is the HO2S voltage within the specified range?

0.425-0.500 V

Go to Step 5

Go to Step 6

5 |

1. Turn OFF the ignition.
2. Connect a 3-amp fused jumper wire between the HO2S 1 high signal circuit, and the HO2S 1 low reference circuit.
3. Turn ON the ignition, with the engine OFF.
4. Observe the HO2S 1 voltage on the scan tool.

Does the scan tool display less than the specified amount?

25 mV

Go to Step 8

Go to Step 6

6 |

1. Turn OFF the ignition.
2. Disconnect both PCM connectors. Refer to Powertrain Control Module Replacement .
3. Measure the resistance of each of the following circuits with a DMM:

• | HO2S 1 high signal circuit between HO2S connector and the PCM connector

• | HO2S 1 low reference circuit between HO2S connector and the PCM connector

• | HO2S 1 low reference loop between pin C1-29 and pin C2-80 of the PCM connectors--Refer to Circuit Testing in Wiring Systems.

Is the resistance of each circuit less than the specified value?

5 ohms

Go to Step 11

Go to Step 7

7 | Repair the circuit that measured a high resistance or an open. Refer to Wiring Repairs in Wiring Systems. Did you complete the repair? | -- | Go to Step 14 | --
8 |

1. Remove the jumpers from the HO2S 1 terminals.
2. Connect a test lamp between the HO2S heater ignition voltage circuit, and heater low control circuit terminals on the engine harness side.
3. Start the engine.

Does the test lamp illuminate?

--

Go to Step 9

Go to DTC P0135

9 | Inspect for the following conditions that may affect the HO2S operation: 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.

• | HO2S for contamination

Notice: Do not remove the pigtail from either the heated oxygen sensor (HO2S) or the oxygen sensor (O2S). Removing the pigtail or the connector will affect sensor operation.

Handle the oxygen sensor carefully. Do not drop the HO2S. Keep the in-line electrical connector and the louvered end free of grease, dirt, or other contaminants. Do not use cleaning solvents of any type. Do not repair the wiring, connector or terminals. Replace the oxygen sensor if the pigtail wiring, connector, or terminal is damaged. This external clean air reference is obtained by way of the oxygen sensor signal and heater wires. Any attempt to repair the wires, connectors, or terminals could result in the obstruction of the air reference and degraded sensor performance. The following guidelines should be used when servicing the heated oxygen sensor:

• | Do not apply contact cleaner or other materials to the sensor or vehicle harness connectors. These materials may get into the sensor causing poor performance.

• | Do not damage the sensor pigtail and harness wires in such a way that the wires inside are exposed. This could provide a path for foreign materials to enter the sensor and cause performance problems.

• | Ensure the sensor or vehicle lead wires are not bent sharply or kinked. Sharp bends or kinks could block the reference air path through the lead wire.

• | Do not remove or defeat the oxygen sensor ground wire, where applicable. Vehicles that utilize the ground wired sensor may rely on this ground as the only ground contact to the sensor. Removal of the ground wire will cause poor engine performance.

• | Ensure that the peripheral seal remains intact on the vehicle harness connector in order to prevent damage due to water intrusion. The engine harness may be repaired using Packard's Crimp and Splice Seals Terminal Repair Kit. Under no circumstances should repairs be soldered since this could result in the air reference being obstructed.

• | Chafed, burnt, cut, pinched, or otherwise damaged HO2S wiring

• | The HO2S must have a clean air reference in order to function properly. This clean air reference is obtained by way of the HO2S wires. Obstruction of the air reference and degraded HO2S performance could result from any attempt to repair the above conditions.

• | Exhaust system leaks or restrictions

• | Evaporative Emissions (EVAP) canister purge--Inspect the EVAP control system. Refer to Inspection/Maintenance Evaporative Emission System Set .

• | The fuel pressure--Incorrect fuel pressure can affect HO2S operation. Refer to Fuel System Diagnosis .

Did you find and correct the condition?

--

Go to Step 14

Go to Step 10

10 | Inspect for poor connections at the HO2S 1 connector. Refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 14 | Go to Step 12
11 | Inspect for poor connections at the PCM harness connectors. Refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 14 | Go to Step 13
12 | Replace the HO2S 1 sensor. Refer to Heated Oxygen Sensor 1 Replacement . Did you complete the replacement? | -- | Go to Step 14 | --
13 | Replace the PCM. Refer to Powertrain Control Module Replacement . Did you complete the replacement? | -- | Go to Step 14 | --
14 |

1. Clear the DTCs with a scan tool.
2. Turn OFF the ignition for 30 seconds.
3. Start the engine.
4. Operate the vehicle within the Conditions for Running the DTC as specified in the supporting text.

Does the DTC run and pass?

--

Go to Step 15

Go to Step 2

15 | With a scan tool, observe the stored information, Capture Info. Does the scan tool display any DTCs that you have not diagnosed? | -- | Go to Diagnostic Trouble Code (DTC) List | System OK