Circuit Description
In order to control the emissions, a catalytic converter converts any harmful exhaust emissions into harmless water vapor and carbon dioxide.
The powertrain control module (PCM) can monitor this process by using a rear heated oxygen sensor (HO2S 2). The HO2S 2, located in the exhaust stream past the catalytic converter, produces an output signal which indicates the storage capacity of the catalyst. This signal indicates the catalyst's ability to effectively convert the exhaust emissions. If the catalyst is functioning properly, the HO2S 2 signal will be far less active than the signal produced by the front heated oxygen sensor (HO2S 1).
Do not attempt to repair the HO2S 2. Replace the entire HO2S 2 assembly if the following conditions exist, :
| • | Damaged wiring |
| • | Damaged electrical connectors |
| • | Damaged terminals |
Obstruction of the air reference and degraded HO2S 2 performance can result from any attempt to repair the above conditions.
The HO2S must have a clean air reference in order for the HO2S 2 to function properly. This clean air reference is obtained by way of the HO2S 2 wires.
Conditions for Running the DTC
| • | DTCs P0105, P0107, P0108, P0112, P0113, P0117, P0118, P0122, P0123, P0201, P0202, P0203, P0204, P0205, P0206, P0300, P0336, P0440, P0446, P0452, P0453, P0507, P0601, P0602, P0604, P0606, P1120, P1220, P1221, P1271, P1275, P1280, P1484, P1512, P1514, P1515, P1516, P1621, P1635, P1639, P1680, or P1681 are not set. |
| • | The engine is in the decel fuel cut-off (DFCO) mode. |
| • | The ignition 1 signal is more than 10 volts. |
| • | The engine coolant temperature (ECT) is greater than 70°C (158°F). |
| • | The fuel level sensor is more than 10 percent. |
| • | The engine is operating in Closed Loop. |
| • | The engine run time is more than 10 seconds. |
Conditions for Setting the DTC
The HO2S 2 remains more than 648 mV for more than 10 seconds. The diagnostic then will run for 11 seconds after a 10 second delay in order to complete 1 test.
Action Taken When the DTC Sets
| • | The malfunction indicator lamp (MIL) will illuminate after 2 consecutive ignition cycles in which the diagnostic runs with the malfunction present. |
| • | The PCM will record the operating conditions when 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 3 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 in order to clear the DTCs. |
Diagnostic Aids
Check for the following conditions:
| • | A rich exhaust--An overly rich exhaust may load the catalyst causing high HO2S 2 signal voltages. |
| • | Silicone contamination--Silicone contamination of HO2S 2 could cause a false rich condition . A powdery white deposit on the sensor will indicate this condition. |
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 | |||||||||||||
2 |
Does the voltage measure above the specified value? | 946 mV | Go to Step 4 | Go to Step 3 | ||||||||||||
3 |
Does the DTC fail this ignition? | -- | Go to Step 4 | |||||||||||||
4 |
Is the HO2S voltage near the value specified? | 447 mV | Go to Step 5 | Go to Step 6 | ||||||||||||
5 | The HO2S is detecting a rich exhaust condition or may be contaminated. Check for one of the following conditions:
Repair any of the above or similar engine conditions as necessary. Did you find and correct the condition? | -- | Go to Step 9 | Go to Step 7 | ||||||||||||
6 | Test the HO2S high signal circuit for a short to voltage. Refer to Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 9 | Go to Step 8 | ||||||||||||
7 |
Important: Before replacing a contaminated HO2S, determine and repair the cause of the contamination. Replace the HO2S. Refer to Heated Oxygen Sensor 2 Replacement . Did you complete the replacement? | -- | Go to Step 9 | -- | ||||||||||||
8 | Replace the PCM. Refer to Powertrain Control Module Replacement . Did you complete the replacement? | -- | Go to Step 9 | -- | ||||||||||||
9 |
Does the DTC run and pass? | -- | Go to Step 10 | Go to Step 2 | ||||||||||||
10 | With a scan tool, observe the stored information, Capture Info. Does the scan tool display any DTCs that you have not diagnosed? | -- | System OK | |||||||||||||
