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 engine control module (ECM) supplies the HO2S with a reference, or bias, voltage of about 450 mV. When the engine is first started the ECM 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 ECM monitors the rich-to-lean and lean-to-rich transitions. A transition is defined as the HO2S voltage changes from above 600 mV to below 300 mV or from below 300 mV to above 600 mV. If the ECM 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 P0037, P0038, P0106, P0107, P0108, P0112, P0113, P0117, P0118, P0122, P0123, P0125, P0130, P0133, P0137, P0138, P0140, P0171, P0172, P0300, P0336, P0340, P0341, P0455, P0500, P0601, P0602, P0606, P0641, P0722, P0723, P1133 are not set. |
| • | The Engine Speed parameter is between 1,500-3,200 RPM. |
| • | The Loop Status parameter is closed. |
| • | The Air Flow parameter is between 7-25 g/s. |
| • | DTC P1134 runs once per drive cycle when the above conditions are met for 100 seconds. |
Conditions for Setting the DTC
| • | The ECM detects that the HO2S 1 Transition Time Ratio is less than 0.375 or more than 2.375. |
| • | DTC P1134 sets within 60 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. |
Step | Action | Value(s) | Yes | No | ||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
Schematic Reference: Engine Controls Schematics Connector End View Reference: Engine Controls Connector End Views or Powertrain Control Module Connector End Views | ||||||||||||
1 | Did you perform the Diagnostic System Check - Vehicle? | -- | Go to Step 2 | |||||||||
2 |
Is the HO2S 1 voltage parameter varying 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 HO2S 1 voltage parameter less than the specified value? | 100 mV | Go to Step 6 | Go to Step 5 | ||||||||
5 | Is the HO2S 1 voltage parameter more than the specified value? | 800 mV | Go to Step 7 | Go to Step 9 | ||||||||
6 | Test the HO2S 1 high signal circuit for a short to ground. Refer to Circuit Testing and Wiring Repairs . Did you find and correct the condition? | -- | Go to Step 17 | Go to Step 8 | ||||||||
7 |
Important: The sensor may be damaged if the circuit is shorted to a voltage source. Test the HO2S 1 high signal circuit for a short to voltage. Refer to Circuit Testing and Wiring Repairs . Did you find and correct the condition? | -- | Go to Step 17 | Go to Step 16 | ||||||||
8 | Test the HO2S 1 high signal circuit for a short to the HO2S low signal circuit or to the HO2S heater low control circuit. Refer to Circuit Testing and Wiring Repairs . Did you find and correct the condition? | -- | Go to Step 17 | Go to Step 16 | ||||||||
9 |
Is the HO2S 1 voltage parameter less than the specified value? | 100 mV | Go to Step 10 | Go to Step 12 | ||||||||
10 |
Is the HO2S 1 voltage parameter less than the specified value? | 100 mV | Go to Step 13 | Go to Step 11 | ||||||||
11 | Test the HO2S 1 low signal circuit for an open. Refer to Circuit Testing and Wiring Repairs . Did you find and correct the condition? | -- | Go to Step 17 | Go to Step 14 | ||||||||
12 | Test the HO2S 1 high signal circuit for an open. Refer to Circuit Testing and Wiring Repairs . Did you find and correct the condition? | -- | Go to Step 17 | Go to Step 14 | ||||||||
13 | Test for an intermittent and for a poor connection at 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 17 | Go to Step 15 | ||||||||
14 | Test for an intermittent and for a poor connection at the engine control module (ECM). Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs . Did you find and correct the condition? | -- | Go to Step 17 | Go to Step 16 | ||||||||
15 |
Notice: Refer to Silicon Contamination of Heated Oxygen Sensors Notice in the Preface section. Important: The HO2S may be damaged due to contamination. Prior to replacing the HO2S inspect for the following sources of contamination:
Replace the HO2S 1. Refer to Heated Oxygen Sensor 1 Replacement . Did you complete the replacement? | -- | Go to Step 17 | -- | ||||||||
16 | Replace the ECM. Refer to Control Module References for replacement, setup, and programming. Did you complete the replacement? | -- | Go to Step 17 | -- | ||||||||
17 |
Did the DTC fail this ignition? | -- | Go to Step 2 | Go to Step 18 | ||||||||
18 | Observe the Capture Info with a scan tool. Are there any DTCs that have not been diagnosed? | -- | System OK | |||||||||
