Circuit Description
When the vehicle is first started, the engine operates in an Open Loop operation, ignoring the heated oxygen sensor signal and calculating the air/fuel ratio based on inputs from the engine coolant temperature (ECT), the throttle position (TP), and the manifold absolute pressure (MAP) sensors only. The powertrain control module (PCM) will begin by using the heated oxygen sensor (HO2S) signal for controlling the fuel delivery (Closed Loop) when the following conditions are met:
| • | The engine has run a minimum amount of time based on ECT at engine start up. |
| • | The heated oxygen sensor (HO2S) 1 has a varying voltage output showing that the sensor is hot enough to operate properly. |
| • | The ECT has increased a minimum amount based on the ECT at engine start up. |
Conditions For Running The DTC
| • | DTCs P0105, P0107, P0108, P0116, P0117, P0118, P0122, P0123, P0125, P0131, P0132, P0133, P0134, P0201, P0202, P0203, P0204, P0205, P0206, P0300-P0306, P0335, P0336, P0351-P0356, P0601, P0602, P0604, P0606, P1120, P1133, P1220, P1221, P1271, P1275, P1280, P1484, P1512, P1514, P1515, P1516, P1635, P1639, or P1681 are not set. |
| • | The engine run time is more than 100 seconds. |
| • | The engine speed is between 1,200-3,400 RPM. |
| • | The TP indicated angle is between 15-50 percent. |
| • | The ECT sensor is more than 80°C (176°F). |
| • | The accelerator pedal position (APP) indicated angle is more than 1.2 percent. |
| • | The above conditions have been met for 5 seconds. |
Conditions For Setting The DTC
The engine is in Open Loop for 7.5 seconds out of 12.5 seconds.
Action Taken When the DTC Sets
| • | The malfunction indicator lamp (MIL) will illuminate after two consecutive ignition cycles in which the diagnostic runs with the malfunction present. |
| • | The PCM will record the operating conditions at the time that the diagnostic fails. This information will store in the Freeze Frame/Failure Records buffers. |
| • | A history DTC stores. |
Conditions for Clearing the MIL/DTC
| • | The MIL will turn OFF after three consecutive ignition cycles in which the diagnostic runs without a fault. |
| • | A history DTC will clear after 40 consecutive warm up cycles without a fault. |
| • | Use a scan tool to clear the DTCs. |
Test Description
The numbers below refer to the step numbers on the diagnostic table.
-
When the system is operating correctly the HO2S voltage should toggle above and below the specified values.
-
The specified value is what is measured on a correctly operating system.
-
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: Engine Controls Connector End Views | ||||||||||
1 | Did you perform the Diagnostic System Check-Engine Controls? | -- | Go to Step 2 | |||||||
|
Important: If any other DTCs are set, except HO2S DTCs, refer to other DTCs first before proceeding with this table.
Does scan tool indicate HO2S voltage varying outside the specified values? | 400-500 mV | Go to Step 3 | Go to Step 4 | |||||||
3 |
Does the DTC fail this ignition? | -- | Go to Step 4 | |||||||
4 | Inspect and test for the following conditions:
Did you find and correct the condition? | -- | Go to Step 13 | Go to Step 5 | ||||||
Does the voltage measure near the specified value? | 450 mV | Go to Step 6 | Go to Step 8 | |||||||
Does the scan tool indicate HO2S 1 voltage at or near the specified value? | 0 mV | Go to Step 9 | Go to Step 7 | |||||||
7 | Test the low signal circuit for an open high resistance or a short to voltage . Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 13 | Go to Step 11 | ||||||
8 | Test the high signal circuit for an open high resistance or a short to voltage . Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 13 | Go to Step 11 | ||||||
9 | Test for poor connections at the HO2S. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 13 | Go to Step 10 | ||||||
10 |
Important: Determine the cause of contamination before replacing the sensor. Inspect and test for the following conditions:
Notice: Refer to Silicon Contamination of Heated Oxygen Sensors Notice in the Preface section.
Replace the HO2S. Refer to Heated Oxygen Sensor 1 Replacement . Did you complete the replacement? | -- | Go to Step 13 | -- | ||||||
11 | Test for poor connections at the PCM. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 13 | Go to Step 12 | ||||||
12 | Replace the PCM. Refer to Powertrain Control Module Replacement . Did you complete the replacement? | -- | Go to Step 13 | -- | ||||||
13 |
Does the DTC run and pass? | -- | Go to Step 14 | Go to Step 2 | ||||||
14 | With a scan tool, observe the stored information, Capture Info. Does the scan tool display any DTCs that you have not diagnosed? | -- | System OK | |||||||
