Circuit Description
In order to control emissions, a catalytic converter is used to convert harmful exhaust gases into harmless water vapors and carbon dioxide.
The PCM has the capability of monitoring this process by using a rear heated oxygen sensor (HO2S 2). The HO2S 2, located in the exhaust stream behind the catalytic converter, produces an output signal which indicates the storage capacity of the catalyst. This in turn indicates the catalyst's ability to convert the exhaust emissions effectively. If the catalyst is functioning properly, the HO2S 2 signal will be far less active than the signal produced by the front oxygen sensor (O2S 1).
Conditions for Running the DTC
The following DTCs are not set: P0105, P0107, P0108, P0112, P0113, P0117, P0118, P0122, P0123, P0171, P0201, P0202, P0203, P0204, P0300, P0335, P0440, P0442, P0446, P0506, P0507, P0601, P0602 and P1441.
| • | The engine coolant temperature (ECT) is less than 45°C (113°F). |
| • | The intake air temperature (IAT) is less than 45°C (113°F). |
| • | The difference between the ECT and the IAT is less than 7°C (13°F). |
| • | The throttle position (TP) is less than 18 percent. |
| • | The engine run time is less than 400 seconds. |
| • | The average air flow is less than 20 g/s. |
| • | The battery voltage is between 11.6 and 16 V. |
Conditions for Setting the DTC
The HO2S 2 voltage increases less than 150 mV in a certain number of seconds, based upon airflow (g/sec).
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 at the time that the diagnostic fails. This information will store in the Freeze Frame and Failure Records buffers. |
| • | A history DTC stores. |
Conditions for Clearing the 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. |
| • | Clear the DTC with a scan tool. |
Diagnostic Aids
| • | Inspect the exhaust system for the following conditions: |
| - | Any leaks between the 3-way catalytic converter and the flange. |
| - | Any corrosion between the 3-way catalytic converter and the flange |
| - | Any loose or missing hardware between the 3-way catalytic converter and the flange |
| • | A poor electrical connection or a damaged harness. Inspect the harness for a short to ground in the HO2S 2 signal circuit. Ensure that the HO2S 2 pigtail is not contacting the exhaust. |
| Inspect for the following conditions: |
| - | Any wiring contacting the exhaust system |
| - | Any incorrect mating |
| - | Any broken locks |
| - | Any incorrectly formed harness connectors |
| - | Any damaged terminals |
| - | A poor terminal-to-wire connection |
| - | A damaged harness |
| • | Observe the HO2S 2 on a scan tool while moving any of the related connectors and the wiring harness with the ignition on. If the malfunction is induced, the HO2S 2 display will change. This should help isolate the location of the malfunction. |
An intermittent could be the result of the following conditions:
| • | A poor electrical connection |
| • | A rubbed-through wire insulation |
| • | A broken wire inside of the insulation |
Do not attempt to repair the HO2S 2. Replace the HO2S 2 assembly if the following conditions exist:
| • | Any damaged wiring |
| • | A damaged connector |
| • | Any damaged terminals |
Obstruction of the air reference and degraded HO2S 2 performance could result from any attempt to repair the above conditions.
The HO2S 2 must have a clean air reference in order to function properly. This clean air reference is obtained by the HO2S 2 wires.
Test Description
An example test description follows:
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This step determines if DTC P0141 is the result of a hard malfunction or an intermittent condition. With the ignition switch on and the engine off, the HO2S 2 voltage should change within several minutes towards 0 or 1 volt, indicating that the heater is working properly.
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This step determines if the HO2S 2 has a internal short.
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This step determines if the HO2S 2 has a internal open.
Step | Action | Values | Yes | No | ||||
|---|---|---|---|---|---|---|---|---|
1 | Did you perform the Powertrain On-Board Diagnostic (OBD) System Check? | -- | Go to Step 2 | |||||
|
Important: The HO2S must be cool before proceeding with diagnosis. The Ignition must remain OFF for at least one half hour before proceeding with diagnosis.
Does the HO2S voltage increase or decrease from the initial voltage by at least the value specified? | 150 m V | Go to Diagnostic Aids | Go to Step 3 | |||||
3 | Test the ERLS fuse. Did you find an open fuse? | -- | Go to Step 4 | Go to Step 5 | ||||
Is the HO2S 2 heater resistance within the specified range? | 4-6 ohms | Go to Step 9 | Go to Step 10 | |||||
5 |
Does the test lamp illuminate? | -- | Go to Step 6 | Go to Step 7 | ||||
Connect the test lamp between the HO2S 2 ignition feed circuit and the ground circuit at the connector. Does the test lamp illuminate? | -- | Go to Step 10 | Go to Step 8 | |||||
7 |
Did you find and correct the condition? | -- | Go to Step 11 | -- | ||||
8 |
Did you find and correct the condition? | -- | Go to Step 11 | -- | ||||
9 |
Did you complete the repair? | -- | Go to Step 11 | -- | ||||
10 |
Did you complete the repair? | -- | Go to Step 11 | -- | ||||
11 |
Does the DTC reset? | -- | Go to Step 2 | System OK |
