Circuit Description
The HO2S 2, located in the exhaust stream past the catalytic converter, produces an output signal relative to the oxygen storage capacity of the catalytic converter. The PCM can then determine the ability of the catalytic converter to convert the exhaust emissions effectively. The HO2S 2 signal will be far less active than the signal produced by the front Oxygen Sensor 1 (O2S 1).
Conditions for Setting the DTC
| • | DTCs P0106, P0107, P0112, P0113, P0117, P0118, P0121, P0122, P0123, P0200, P0300, P0301, P0302, P0303, P0304, P0404, P0405, P0506, P0507, P1404 P1441 not set. |
| • | Engine run time is greater than 25 seconds. |
| • | Engine Coolant Temperature (ECT) is greater than 40°C (104°F). |
| • | Air/fuel ratio is between 14.5:1 and 14.7:1. |
| • | Throttle Position (TP) angle is between 5% and 50%. |
| • | Engine has met the above conditions for 140 seconds. |
| • | HO2S 2 remains below 43 mV for up to 150 seconds. |
Action Taken When the DTC Sets
| • | The malfunction indicator lamp (MIL) will illuminate. |
| • | The PCM will record the operating conditions at the time that the diagnostic fails. The Freeze Frame and Failure Records buffers will store this information. |
| • | A history DTC stores. |
Conditions for Clearing the MIL/DTC
| • | The malfunction indicator lamp (MIL) will turn OFF after 3 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
Whenever the oxygen sensor pigtail wiring, connector or terminal are damaged, the entire oxygen sensor assembly must be replaced. Do not attempt to repair the wiring, connector or terminals. In order for the O2S to function properly, the O2S must have a clean air reference. This clean air reference is obtained by way of the oxygen sensor wires. Any attempt to repair the wires, connectors or terminals could result in the obstruction of the air reference and degrade the oxygen sensors performance.
A rubbed through wire insulation or a wire contacting the exhaust may cause an intermittent.
Check for the following conditions:
| • | The exhaust system - Inspect the exhaust system for leaks. Check exhaust between the three way catalytic converter and the flange for leaks, corrosion, or for loose or missing hardware and repair as necessary. |
| • | A poor connection or damaged harness - Inspect the harness for a short to ground in rear HO2S 2 high circuit, improper mating, or broken locks. Ensure that the HO2S 2 pigtail is not contacting the exhaust. |
| • | An intermittent test - Observe the rear HO2S 2 on the scan tool while moving related connectors and wiring harness with the key ON. Whenever the fault is induced, the rear HO2S 2 display will change. This may help isolate the location of the malfunction. |
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 malfunction 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 malfunction or an intermittent condition.
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Jumping HO2S 2 ground circuit 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.
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Replacement PCMs must be reprogrammed and the crankshaft position system variation procedure must be performed. Refer to the latest Techline information for PCM reprogramming and also refer to the Powertrain Control Module (PCM) for the Crankshaft Position System Variation Procedure.
Step | Action | Value(s) | Yes | No |
|---|---|---|---|---|
Was the Powertrain On-Board Diagnostic (OBD) System Check performed? | -- | Go to | ||
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 DTCs are set. Are any DTCs displayed that have not been diagnosed? | -- | Go to applicable DTC table | System OK |
