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
| • | DTC's P0106, P0107, P0112, P0113, P0117, P0118, P0121, P0122, P0123, P0200, P0300, P0301, P0302, P0303, P0304, P0506, P0507, P1406, P1441 not set. |
| • | Engine run time is greater than 25 seconds. |
| • | Engine coolant temperature is greater than 40° C (104° F). |
| • | Throttle Position (TP) between 5 % and 50 %. |
| • | Air/fuel ratio between 14.5:1 and 14.7:1. |
| • | Above conditions met for 140 seconds. |
| • | HO2S 2 remains below 43 mV for 112 to 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. |
| • | The MIL/DTCs can be cleared by using the scan tool. |
Diagnostic Aids
| • | The exhaust system--Inspect the exhaust system for the following conditions: |
| - | Exhaust system leaks between the three-way catalytic converter and the flange |
| - | Exhaust system corrosion between the three-way catalytic converter and the flange |
| - | Exhaust system loose or missing hardware between the three-way catalytic converter and the flange |
| - | 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 connections |
| - | 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 isolate the location of the malfunction. |
An intermittent could be the result of the following conditions:
| • | A poor electrical connection |
| • | Rubbed-through wire insulation |
| • | A broken wire inside of the insulation |
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.
Test Description
Number(s) below refer to the step number(s) on the Diagnostic Table.
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The Powertrain OBD System Check prompts the technician to complete some basic checks and store the freeze frame and failure records data on the scan tool if applicable. This creates an electronic copy of the data taken when the fault occurred. The information is then stored on the scan tool for later reference.
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This step determines if DTC P0137 is the result of a hard failure or an intermittent condition.
-
Jumping CKT 1669 to ground is necessary to allow the PCM to display the supplied bias voltage. If the voltage is between 0.35 and 0.55 volt, then the wiring and PCM are OK.
-
Replacement PCM's must be reprogrammed. Refer to the latest Techline information for programming procedures.
Step | Action | Value(s) | Yes | No |
|---|---|---|---|---|
Was the Powertrain On-Board Diagnostic (OBD) System Check performed? | -- | |||
Is the HO2S 2 voltage less than the specified value? | 200 mV (0.02V) | |||
3 |
Is the HO2S 2 voltage less than the specified value? | 40 mV (0.40V) | ||
Disconnect the HO2S 2 electrical connector and jumper the HO2S 2 sensor low circuit (PCM side) to ground. Does the scan tool indicate the HO2S 2 voltage within the specified value? | 350 mV-550 mV (0.35V-0.55V) | |||
5 |
Was a repair necessary? | -- | ||
Replace the PCM. Is the action complete? | -- | -- | ||
7 | Replace the HO2S 2 sensor. Is the action complete? | -- | -- | |
8 |
Does the scan tool indicate that this diagnostic has ran and passed? | -- | ||
9 | Check if any additional DTC's are set. Are any DTC's displayed that have not been diagnosed? | -- | Go to applicable DTC table | System OK |
