Circuit Description
In order to control 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 connector |
| • | Damaged terminals |
Obstruction of the air reference and a degraded HO2S 2 performance can result from any attempt to repair the above conditions.
The HO2S 2 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 power enrichment mode. |
| • | The ignition 1 signal is more than 10 volts. |
| • | The engine coolant temperature (ECT) is greater than 70°C (158°F). |
| • | Then engine is operating in Closed Loop. |
| • | The fuel level sensor is more than 10 percent. |
| • | The engine run time is more than 10 seconds. |
Conditions For Setting The DTC
The HO2S 2 remains less than 400 mV for more than 5 seconds. The diagnostic will then run for 11 seconds after a 5 second delay.
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
| • | Inspect the exhaust system for the following conditions: |
| - | Leaks |
| - | Corrosion between 3-way catalytic converter and the flange |
| - | Loose or missing hardware |
| - | Repair any conditions as necessary. |
| • | A poor electrical connection or a damaged harness--Inspect the harness for a short to ground in the HO2S 2 high signal circuit. Ensure that the HO2S 2 pigtail is not contacting the exhaust. |
| Check for the following conditions: |
| - | Wiring contacting the exhaust system |
| - | Improper mating |
| - | Broken locks |
| - | Improperly-formed harness connectors |
| - | Damaged terminals |
| - | Poor terminal-to-wire connections |
| - | A damaged harness |
| • | Intermittent test--Observe the HO2S 2 on the scan tool while moving any of the related electrical connectors and the wiring harness with the ignition ON. If the malfunction is induced, the HO2S 2 display will change. This procedure should help isolate the location of the malfunction. |
An intermittent can be the result of the following conditions:
| • | A poor electrical connection |
| • | Rubbed-through wire insulation |
| • | Broken wire inside the insulation |
Obstruction of the air reference and a degrade HO2S 2 performance can result from any attempt to repair the HO2S harness or the connector.
The HO2S 2 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.
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 remain below the specified value? | 400 mV | Go to Step 4 | Go to Step 3 |
3 |
Does the DTC fail this ignition? | -- | Go to Step 4 | |
4 |
Does scan tool indicate HO2S 1 voltage less than the specified value? | 400 mV | Go to Step 5 | Go to Step 7 |
5 | Test the HO2S high signal circuit for a short to ground or a short to the HO2S low signal circuit. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 8 | Go to Step 6 |
6 | Replace the PCM. Refer to Powertrain Control Module Replacement . Did you complete the replacement? | -- | Go to Step 8 | -- |
7 |
Did you complete the replacement? | -- | Go to Step 8 | -- |
8 |
Does the DTC run and pass? | -- | Go to Step 9 | Go to Step 2 |
9 | With a scan tool, observe the stored information, Capture Info. Does the scan tool display any DTCs that you have not diagnosed? | -- | System OK | |
