Circuit Description
In order to control emissions, a catalytic converter is used to convert harmful exhaust emissions into harmless water vapor and carbon dioxide.
The powertrain control module (PCM) has the capability to 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 in turn indicates the catalyst's ability to convert 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).
If the O2S pigtail wiring, connector, or terminal are damaged the entire O2S assembly must be replaced. DO NOT attempt to repair the wiring, connector, or terminals. In order for the sensor to function properly, it must have a clean air reference provided to it. This clean air reference is obtained by way of the O2S wires. Any attempt to repair the wires, connectors, or terminals could result in the obstruction of the air reference and degrade oxygen sensor performance. Refer to Section 8A-5, Heated Oxygen Sensor (HO2S) Repair.
Conditions for Setting
| • | HO2S 2 voltage changes less than 150 mV in 100-190 seconds. |
| • | Engine coolant temperature is greater than 40°C (104°F). |
| • | Intake air temperature (IAT) is less than 40°C (104°F). |
| • | The difference between ECT and IAT is less than 5°C (41°F). |
| • | The throttle position (TP) is less than 15 percent for more than 15 seconds. |
Action Taken
Malfunction indicator lamp (MIL) illuminates after two consecutive driving cycles with the fault active.
Conditions for Clearing the MIL/DTC
| • | The MIL will turn OFF after passing three consecutive diagnostic tests. |
| • | A history DTC will clear after 40 consecutive ignition cycles have occurred without a fault. |
| • | History and current DTCs can be cleared by using a scan tool. |
Diagnostic Aids
| • | An intermittent may be caused by a rubbed through wire insulation, or a wire contacting the exhaust. |
| • | Inspect for a poor connection or damaged harness--Inspect the PCM harness for open in CKT 1668, improper mating, broken locks, improperly formed or damaged terminals, poor terminal to wire connection and damaged harness. |
Test Description
The number below refers to the step number on the diagnostic table.
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This step determines if DTC P0141 is the result of a hard failure or an intermittent condition. With the ignition ON and the engine OFF, the HO2S 2 voltage displayed on the scan tool should change within several minutes towards 0 or 1 volt, indicating that the heater is working properly.
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Probing terminal D of the HO2S 2 connector verifies if voltage is available to the HO2S 2 heater.
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If voltage is available at the connector then it becomes a good voltage source to check for a ground at terminal C.
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Determines if voltage is not available at the HO2S 2 due to an open O2 fuse or an open ignition feed CKT 241. If the fuse is open, determine if it was due to a short in the ignition feed circuit before replacing the fuse.
Step | Action | Values | Yes | No |
|---|---|---|---|---|
Schematic Reference: Engine Controls Schematics | ||||
1 | Was the On-Board Diagnostic (OBD) System Check performed? | -- | Go to Step 2 | |
|
Important: If the engine has just been operating allow the engine to cool for about one half hour before proceeding.
Does it? | 0 V or 1 V | Go to Diagnostic Aids | Go to Step 3 | |
Does the test light illuminate? | -- | Go to Step 4 | Go to Step 5 | |
Connect a test light between the ignition feed and ground circuits, PCM side of the connector. Does the test light illuminate? | -- | Go to Step 6 | Go to Step 7 | |
Inspect the fuse in the fuse block. Is the fuse blown? | -- | Go to Step 8 | Go to Step 9 | |
6 | Check the connections at the HO2S 2 connector and repair as necessary. Was a repair necessary? | -- | Go to Step 10 | |
7 | Check the connections at the HO2S 2 connector and repair as necessary. Was a repair necessary? | -- | Go to Step 11 | |
8 |
Is the action complete? | -- | -- | |
9 | Check the connections at the HO2S 2 connector and repair if necessary. Was a repair necessary? | -- | Go to Step 12 | |
10 | Replace the HO2S 2. Is the action complete? | -- | -- | |
11 | Repair open ground circuit. Is the action complete? | -- | -- | |
12 | Repair open ignition feed circuit. Is the action complete? | -- | -- | |
