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 catalysts 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 connector |
| • | Damaged terminals |
Obstruction of the air reference and degrade 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.
Conditions for Running the DTC
| • | DTCs P0105, P0107, P0108, P0112, P0113, P0117, P0118, P0122, P0123, P0171, P0201, P0202, P0203, P0204, P0300, P0335, P0440, P0442, P0446, P0506, P0507, P0601, P0602, or P1441 not set. |
| • | Air flow is more than 5.5 grams per second. |
| • | Engine coolant temperature (ECT) is more than 40°C (104°F). |
| • | Throttle position (TP) angle is between 5 percent and 50 percent for 4 seconds. |
Conditions For Setting The DTC
HO2S 2 remains below 22 mV for 150 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. |
| • | 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 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. |
| Check for the following conditions: |
| - | Wiring contacting the exhaust system |
| - | Improper mating |
| - | Broken locks |
| - | Improperly formed harness connectors |
| - | Damaged terminals |
| - | Poor terminal-to-wire connection |
| - | 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 isolate the location of the malfunction. |
An intermittent could be the result of the following conditions:
| • | Poor electrical connection |
| • | Rubbed-through wire insulation |
| • | Broken wire inside the insulation |
Obstruction of the air reference and degrade HO2S 2 performance could result in 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.
-
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 malfunction occurred. The scan tool stores this information for later reference.
-
This step determines if DTC P0137 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 .
-
Reprogram the replacement PCM and perform the crankshaft position system variation learn procedure. Refer to the latest Techline™ information for PCM programming.
Step | Action | Value(s) | Yes | No | ||||
|---|---|---|---|---|---|---|---|---|
Did you perform the Powertrain On-Board Diagnostic (OBD) System Check? | -- | |||||||
Is the HO2S 2 voltage less than the specified value? | 22 mV (0.02 V) | |||||||
3 |
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 the HO2S 2 voltage is within the specified value? | 350 mV-550 mV (0.35 V-0.55 V) | |||||||
5 |
Was a repair necessary? | -- | ||||||
|
Important: The replacement PCM must be programmed. Replace the PCM. Refer to the Powertrain Control Module Replacement . Is the action complete? | -- | -- | ||||||
7 |
Caution: Avoid contact with moving parts and hot surfaces while working around a running engine in order to prevent physical injury. Is the action complete? | -- | -- | |||||
8 |
Does the scan tool indicate that this diagnostic ran and passed? | -- | ||||||
9 | Check to see if any additional DTCs are set. Does the scan tool display any DTCs that you have not diagnosed? | -- | System OK |
