Circuit Description
Heated oxygen sensors (HO2S) are used for fuel control and catalyst monitoring. Each HO2S compares the oxygen content of the surrounding air with the oxygen content of the exhaust stream. When the vehicle is started, the control module operates in an Open Loop mode, ignoring the HO2S signal voltage while calculating the air-to-fuel ratio. The control module supplies the HO2S with a reference, or bias, voltage of approximately 450 mV. While the engine runs, the HO2S heats up and begins to generate a voltage within a range of 0-1,000 mV. This voltage will fluctuate above and below the bias voltage. Once sufficient HO2S voltage fluctuation is observed by the control module, Closed Loop is entered. The control module uses the HO2S voltage to determine the air-to-fuel ratio. An HO2S voltage that increases above bias voltage toward 1,000 mV indicates a rich fuel mixture. An HO2S voltage that decreases below bias voltage toward 0 mV indicates a lean fuel mixture.
The heating elements within each HO2S heat the sensor. The powertrain control module (PCM) controls the HO2S heater control circuit. The HO2S heater diagnostic monitors the current draw through the HO2S output driver module (ODM) when the engine is running. This allows the system to enter Closed Loop earlier and the control module to calculate the air-to-fuel ratio sooner.
If the PCM detects that the calculated transition time ratio is incorrect, DTC P1134 will set.
The HO2S 1 has the following circuits:
| • | A HO2S 1 high signal circuit |
| • | A HO2S 1 low reference circuit |
| • | A HO2S 1 heater ignition voltage circuit |
| • | A HO2S 1 heater low control circuit |
DTC Descriptor
This diagnostic procedure supports the following DTC:
DTC P1134 HO2S Transition Time Ratio Bank 1 Sensor 1
Conditions for Running the DTC
The following conditions must be met for at least 1 second:
| • | DTCs P0030, P0053, P0101, P0102, P0103, P0107, P0108, P0112, P0113, P0116, P0117, P0118, P0120, P0125, P0128, P0131, P0132, P0134, P0135, P0201, P0202, P0203, P0204, P0205, P0206, P0300, P0442, P0443, P0446, P0449, P0451, P0452, P0454, P0455, P0464, P0496, P2135, P2A00 are not set. |
| • | DTCs P0401, P0420, and P2A01 are not commanding fuel. |
| • | The system voltage is between 9-18 volts. |
| • | The scan tool special functions are not active. |
| • | The HO2S 1 heater parameter is ON. |
| • | The current misfire condition is not detected. |
| • | The ECT Sensor parameter is more than 65°C (149°F). |
| • | The Engine Run Time parameter is at least 60 seconds. |
| • | The evaporative emission (EVAP) purge solenoid is commanded ON. |
| • | The MAF sensor parameter is between 15-30 g/s. |
| • | The Engine Speed parameter is between 1,300-3,000 RPM. |
| • | The TP Sensor parameter is at least 2 percent. |
| • | The Loop Status parameter is closed. |
| • | The vehicle is not in Park, Reverse, or Neutral. |
Conditions for Setting the DTC
| • | The PCM detects that the HO2S 1 voltage transition time ratio from rich-to-lean and lean-to-rich is incorrect during a 90-second monitoring period. |
| • | This diagnostic runs once per trip. |
Action Taken When the DTC Sets
| • | The control module illuminates the malfunction indicator lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails. |
| • | The control module records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the control module stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the control module records the operating conditions at the time of the failure. The control module writes the operating conditions to the Freeze Frame and updates the Failure Records. |
Conditions for Clearing the MIL/DTC
| • | The control module turns OFF the malfunction indicator lamp (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail. |
| • | A current DTC, Last Test Failed, clears when the diagnostic runs and passes. |
| • | A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic. |
| • | Clear the MIL and the DTC with a scan tool. |
Step | Action | Values | Yes | No | ||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
Schematic Reference: Engine Controls Schematics Connector End View Reference: Powertrain Control Module Connector End Views or Engine Controls Connector End Views | ||||||||||||||||
1 | Did you perform the Diagnostic System Check - Vehicle? | -- | Go to Step 2 | |||||||||||||
2 |
Does the voltage fluctuate rapidly above and below the specified range? | 300-600 mV | Go to Step 3 | Go to Step 4 | ||||||||||||
3 |
Did the DTC fail this ignition? | -- | Go to Step 4 | Go to Testing for Intermittent Conditions and Poor Connections | ||||||||||||
4 |
Is the voltage less than the specified value? | 15 mV | Go to Step 5 | Go to Step 6 | ||||||||||||
5 |
Is the voltage less than the specified value? | 15 mV | Go to Step 8 | Go to Step 7 | ||||||||||||
6 | Test the HO2S 1 high signal circuit for an open or high resistance. Refer to Circuit Testing , Wiring Repairs , and Heated Oxygen Sensor Wiring Repairs . Did you find and correct the condition? | -- | Go to Step 13 | Go to Step 10 | ||||||||||||
7 | Test the HO2S 1 low signal circuit for an open or high resistance. Refer to Circuit Testing , Wiring Repairs , and Heated Oxygen Sensor Wiring Repairs . Did you find and correct the condition? | -- | Go to Step 13 | Go to Step 10 | ||||||||||||
8 | Inspect for the following that may affect the HO2S operation: Notice: Refer to Silicon Contamination of Heated Oxygen Sensors Notice in the Preface section.
Notice: Refer to Heated Oxygen and Oxygen Sensor Notice in the Preface section.
Did you find and correct the condition? | -- | Go to Step 13 | Go to Step 9 | ||||||||||||
9 |
Notice: Refer to Heated Oxygen and Oxygen Sensor Notice in the Preface section. Test for an intermittent and for a poor connection at the HO2S 1. Refer to Testing for Intermittent Conditions and Poor Connections , Connector Repairs , and Heated Oxygen Sensor Wiring Repairs . Did you find and correct the condition? | -- | Go to Step 13 | Go to Step 11 | ||||||||||||
10 | Test for an intermittent and for a poor connection at the powertrain control module (PCM). Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs . Did you find and correct the condition? | -- | Go to Step 13 | Go to Step 12 | ||||||||||||
11 |
Notice: Refer to Heated Oxygen Sensor Resistance Learn Reset Notice in the Preface section. Replace the HO2S 1. Refer to Heated Oxygen Sensor Replacement - Bank 1 Sensor 1 . Did you complete the replacement? | -- | Go to Step 13 | -- | ||||||||||||
12 | Replace the PCM. Refer to Control Module References for replacement, setup, and programming. Did you complete the replacement? | -- | Go to Step 13 | -- | ||||||||||||
13 |
Did the DTC fail this ignition? | -- | Go to Step 2 | Go to Step 14 | ||||||||||||
14 | Observe the Capture Info with a scan tool. Are there any DTCs that have not been diagnosed? | -- | System OK | |||||||||||||
