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) 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 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).
Replace the entire HO2S 2 assembly. Do not attempt to repair the HO2S 2 if the following conditions exist:
| • | Damaged wiring |
| • | Damaged electrical connectors |
| • | 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 for the HO2S 2 to function properly. This clean air reference is obtained by way of the HO2S 2 wires.
Conditions for Setting the DTC
| • | DTCs P0106, P0107, P0112, P0113, P0117, P0118, P0121, P0122, P0123, P0200, P0300, P0301, P0302, P0303, P0304, P0506, P0507, P1336, P1404, P1441 not set. |
| • | The engine has been running longer than 30 seconds. |
| • | The Engine Coolant Temperature (ECT) is greater than 40°C (104°F). |
| • | The Calculated Air Flow is greater than 5.5 g/s for 140 seconds. |
| • | The Throttle Position (TP) is between 4 percent and 56 percent. |
| • | The HO2S 2 remains between 425 mV and 456 mV for 125 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 and Failure Records buffers. |
| • | A history DTC stores. |
| • | The coolant fan turns ON. |
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. |
| • | The MIL/DTCs can be cleared by using the scan tool. |
Diagnostic Aids
An intermittent could be the result of the following conditions:
| • | A poor electrical connection |
| • | Moisture in the electrical connector/wiring |
| • | Rubbed-through wire insulation |
| • | A broken wire inside the insulation |
Check for the following conditions:
| • | A poor electrical connection or a damaged harness--Inspect the PCM harness for an open in the HO2S 2 signal circuit. Check for the following conditions: |
| - | Improper mating |
| - | Broken locks |
| - | Improperly-formed connectors |
| - | Damaged terminals |
| - | A poor terminal-to-wire connection |
| - | A damaged harness |
| • | Intermittent test--Observe the HO2S 2 on the scan tool while moving the related electrical connectors and the wiring harness with the ignition switch ON. If the malfunction is induced, the HO2S 2 display will change. This test should help isolate the location of the malfunction. |
Replace the entire HO2S 2 assembly. Do not attempt to repair the HO2S 2 if the following conditions exist:
| • | Damaged wiring |
| • | Damaged electrical connector |
| • | Damaged terminals |
Obstruction of the air reference and degraded HO2S 2 performance could result in 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.
Test Description
The number(s) below refer(s) to the step number(s) on the Diagnostic Table.
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The Powertrain OBD System Check prompts you to complete some of the basic checks and to store the freeze frame and failure records data on the scan tool if applicable. This creates an electronic copy of the data captured when the fault occurred. The scan tool stores this data for later reference.
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This step determines if DTC P0140 is the result of a hard failure or an intermittent condition.
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Disconnecting the HO2S 2 and jumpering the HO2S 2 signal circuit and the HO2S 2 low circuit to ground will determine if the PCM or wiring or HO2S 2 is malfunctioning.
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This step determines which circuit the malfunction is in. If the HO2S 2 signal circuit and the HO2S 2 low circuit are OK, this is an indication that the PCM connection or the PCM is malfunctioning.
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Reprogram the replacement PCM and perform the crankshaft position system variation learning procedure. Refer to the latest Techline information for PCM programming and Powertrain Control Module (PCM) for the crankshaft position system variation learning procedure.
Step | Action | Value(s) | Yes | No |
|---|---|---|---|---|
Did you perform the Powertrain On-Board Diagnostic (OBD) System Check? | -- | |||
Does the scan tool display an HO2S 2 voltage between the specified value? | 80°C (176°F) 1200 RPM 425 mV-460 mV (0.425 V-0.460 V) | |||
3 |
Does the scan tool display the HO2S 2 voltage steady around the specified value? | 425 mV-460 mV (0.425 V-0.460 V) | ||
Does the scan tool display the HO2S 2 voltage below the specified value? | 100 mV (0.10 V) | |||
5 |
Was a repair necessary? | -- | ||
Does the test light illuminate? | -- | |||
7 | Replace the HO2S 2 sensor. Is the action complete? | -- | -- | |
8 | Check for an open or a poor connection in the HO2S 2 high circuit. Repair the circuit or connection as necessary. Was a repair necessary? | -- | ||
9 | Repair the open in the HO2S 2 low circuit. Is the action complete? | -- | -- | |
Replace the PCM. Is the action complete? | -- | -- | ||
11 |
Does the scan tool indicate that this diagnostic has ran and passed? | -- | ||
12 | Check to see if any additional DTCs are set. Does the scan tool display any DTCs that you have not diagnosed? | -- | Go to applicable DTC table | System OK |
