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 HO2 2 wires.
Conditions for Running the DTC
| • | DTCs P0105, P0107, P0108, P0112, P0113, P0117, P0118, P0122, P0123, P0171, P0172, P0201, P0202, P0203, P0204, P0300, P0336, P0440, P0446, P0452, P0453, P0506, P0507, P0601, P0602, or P1441 not set. |
| • | The engine is in power enrichment mode. |
| • | The battery voltage is more than 10.0 volts. |
| • | The engine coolant temperature (ECT) is more than 75°C (167°F). |
| • | The fuel level is more than 10 percent. |
| • | The engine has been running more than 10 seconds. |
Conditions For Setting The DTC
The HO2S 2 remains at less than 400 mV for more than 5 seconds. The diagnostic then will run for 11 seconds after a 5 second delay.
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. |
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. |
| • | Use a scan tool to clear the DTCs. |
Diagnostic Aids
| • | The exhaust system -- Inspect the exhaust system for the following conditions: |
| - | Leaks |
| - | Corrosion between three-way catalytic converter and the flange |
| - | Loose or missing hardware |
| - | Repair the conditions as necessary. |
| • | A faulty 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: |
| - | Wiring contacting the exhaust system |
| - | Improper mating |
| - | Broken locks |
| - | Improperly formed harness connectors |
| - | Damaged terminals |
| - | Faulty terminal to wire connection |
| - | 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 should help to isolate the location of the malfunction. |
An intermittent could be the result of the following conditions:
| • | A faulty electrical connection |
| • | Rubbed through wire insulation |
| • | Broken wire inside the insulation |
Obstruction of the air reference and degraded HO2S 2 performance could result from any attempt to repair the HO2S harness or 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.
Test Description
The numbers below refer to the step numbers on the Diagnostic Table.
-
This step determines if DTC P1137 is the result of a hard malfunction or an intermittent condition.
-
It is necessary to jump the HO2S 2 low circuit to ground in order to allow the PCM to display the supplied bias voltage. The PCM and the wiring are OK if the voltage is between 0.35 and 0.55 volt .
-
The replacement PCM must be programmed and the Crankshaft Position System Variation Learn procedure must be performed.
Step | Action | Value(s) | Yes | No | ||||
|---|---|---|---|---|---|---|---|---|
1 | Did you perform the Powertrain On-Board Diagnostic (OBD) System Check? | -- | ||||||
2 | Are any DTCs codes set? | -- | Go to applicable DTC | |||||
With the scan tool observe the HO2S 2 voltage. Does the HO2S 2 voltage read less than the specified value? | 22 mV (0.02 V) | |||||||
4 |
Is the HO2S 2 voltage less than the specified value? | 40 mV (0.04 V) | ||||||
Caution: Avoid contact with moving parts and hot surfaces while working around a running engine in order to prevent physical injury. Does the scan tool indicate that the HO2S 2 voltage is within the specified value? | 350 mV-550 mV (0.35 V-0.55 V) | |||||||
6 |
Did you find and correct the condition? | -- | ||||||
|
Important:: The replacement PCM must be programmed. Refer to Powertrain Control Module Replacement/Programming . Replace the PCM. Refer to the Powertrain Control Module Replacement . Did you complete the replacement? | -- | -- | ||||||
8 |
Caution: Avoid contact with moving parts and hot surfaces while working around a running engine in order to prevent physical injury. Did you complete the replacement? | -- | -- | |||||
9 |
Does the DTC reset? | -- | System OK |
