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 in the exhaust stream. The HO2S must reach operating temperature to provide an accurate voltage signal. Heating elements inside the HO2S minimize the time required for the sensors to reach operating temperature. The powertrain control module (PCM) supplies the HO2S with a reference, or bias, voltage of about 450 mV. When the engine is first started the PCM operates in Open Loop, ignoring the HO2S voltage signal. Once the HO2S reaches operating temperatures and Closed Loop is achieved, the HO2S generates a voltage within a range of 0-1,000 mV that fluctuates above and below bias voltage. High HO2S voltage indicates a rich exhaust stream. Low HO2S voltage indicates a lean exhaust stream.
This diagnostic will only run once per ignition cycle. The PCM monitors the number of rich-to-lean and lean-to-rich transitions. If the PCM detects that the transition time ratio is not within a specified range, DTC P1134 will set.
DTC Descriptor
This diagnostic procedure supports the following DTC:
DTC P1134 HO2S Transition Time Ratio Sensor 1
Conditions for Running the DTC
| • | DTCs P0068, P0106, P0107, P0108, P0112, P0113, P0117, P0118, P0120, P0122, P0123, P0125, P0128, P0171, P0172, P0201, P0202, P0203, P0204, P0205, P0206, P0220, P0300-P0306, P0315, P0336, P0442, P0446, P0452, P0453, P0455, P0483, P0496, P0506, P0507, P0601, P0602, P0604, P0606, P060D, P060E, P0641, P0651, P1516, P1621, P2101, P2120, P2125, P2135, P2138, P2176 are not set. |
| • | The Engine Coolant Temperature (ECT) Sensor parameter is more than 70°C (158°F). |
| • | The Engine Speed parameter is between 1,000-3,500 RPM. |
| • | The Ignition 1 Signal parameter is more than 10 volts. |
| • | The Engine Run Time parameter is more than 170 seconds. |
| • | The Loop Status parameter is closed. |
| • | The Throttle Position (TP) Indicated Angle parameter is between 5-60 percent. |
| • | The evaporative emission (EVAP) purge solenoid command is more than 0 percent. |
| • | The Fuel Level Sensor parameter is more than 10 percent. |
| • | The Manifold Absolute Pressure (MAP) Sensor parameter is between 25-104 kPa. |
| • | The Air Flow Calculated parameter is more than 25 g/s. |
| • | DTC P1134 runs once per drive cycle when the above conditions are met for 2 seconds. |
Conditions for Setting the DTC
| • | The PCM detects that the HO2S 1 rich-to-lean or lean-to-rich transitions are less than a calibrated valve. |
| • | DTC P1134 sets within 90 seconds when the above condition is met. |
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. |
Test Description
The numbers below refer to the step numbers on the diagnostic table.
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When the system is operating correctly, the HO2S 1 voltage should toggle above and below the specified values. You may need to operate the vehicle within the Freeze Frame conditions and Conditions for Setting the DTC in order to duplicate the malfunction that was detected by the PCM.
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The specified value is what is measured on a correctly operating system.
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The specified value is what is measured on a correctly operating system.
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 | |||||||||||
|
Important: If any other DTCs are set except for heated oxygen sensor (HO2S) DTCs, refer to the other DTCs first before proceeding with this table.
Does the scan tool indicate that the HO2S 1 voltage is varying above and below the specified values? | 250-500 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 | ||||||||||
Does the voltage measure within the specified range? | 350-550 mV | Go to Step 5 | Go to Step 9 | |||||||||||
Does the scan tool indicate that the HO2S 1 voltage is less than the specified value? | 20 mV | Go to Step 6 | Go to Step 11 | |||||||||||
6 |
Does the test lamp illuminate? | -- | Go to Step 7 | Go to Step 12 | ||||||||||
7 |
Does the test lamp turn ON and OFF with each command? | -- | Go to Step 15 | Go to Step 8 | ||||||||||
8 | Does the test lamp remain illuminated with each command? | -- | Go to Step 13 | Go to Step 14 | ||||||||||
9 | Test the HO2S 1 high signal circuit for the following conditions:
Refer to Circuit Testing and Wiring Repairs . Did you find and correct the condition? | -- | Go to Step 20 | Go to Step 10 | ||||||||||
10 | Test the HO2S 1 low signal circuit for a short to voltage. Refer to Circuit Testing and Wiring Repairs . Did you find and correct the condition? | -- | Go to Step 20 | Go to Step 17 | ||||||||||
11 | Test the HO2S 1 low signal circuit for an open or high resistance. Refer to Circuit Testing and Wiring Repairs . Did you find and correct the condition? | -- | Go to Step 20 | Go to Step 17 | ||||||||||
12 |
Did you find and correct the condition? | -- | Go to Step 20 | Go to Step 16 | ||||||||||
13 | Test the HO2S 1 heater low control circuit for a short to ground. Refer to Circuit Testing and Wiring Repairs . Did you find and correct the condition? | -- | Go to Step 20 | Go to Step 17 | ||||||||||
14 | Test the HO2S 1 heater low control circuit for the following conditions:
Refer to Circuit Testing and Wiring Repairs . Did you find and correct the condition? | -- | Go to Step 20 | Go to Step 17 | ||||||||||
15 |
Important: Before replacing the HO2S 1, inspect and remove any source of contamination. Inspect for the following conditions:
Did you find and correct the condition? | -- | Go to Step 20 | Go to Step 16 | ||||||||||
16 | Inspect for poor connections at the harness connector of the HO2S 1. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs . Did you find and correct the condition? | -- | Go to Step 20 | Go to Step 18 | ||||||||||
17 | Inspect for poor connections at the harness connector of the PCM. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs . Did you find and correct the condition? | -- | Go to Step 20 | Go to Step 19 | ||||||||||
18 |
Notice: Refer to Heated Oxygen Sensor Resistance Learn Reset Notice in the Preface section. Replace the HO2S 1. Refer to Heated Oxygen Sensor 1 Replacement . Did you complete the replacement? | -- | Go to Step 20 | -- | ||||||||||
19 | Replace the PCM. Refer to Control Module References for replacement, setup, and programming. Did you complete the replacement? | -- | Go to Step 20 | -- | ||||||||||
20 |
Did the DTC fail this ignition? | -- | Go to Step 2 | Go to Step 21 | ||||||||||
21 | Observe the Capture Info with a scan tool. Are there any DTCs that have not been diagnosed? | -- | System OK | |||||||||||
