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
| • | The rear HO2S 2 remains between 425 mV and 456 mV for greater than 125 seconds. |
| • | The engine has been running for greater than 30 seconds. |
| • | The Throttle Position (TP) angle is between 5 % and 55 %. |
| • | The engine coolant temperature is greater than 40° C (158° F). |
| • | The vehicle is in a Closed Loop. |
| • | One or more of the following DTCs are not set P0106, P0107, P0108, P0112, P0113, P0117, P0118, P0121, P0122, P0123, P0300-P0304, P0506, P0507, P1406, P1441. |
Action Taken When the DTC Sets
| • | The Malfunction Indicator Lamp (MIL) illuminates after 2 consecutive ignition cycles in which the diagnostic runs with the fault active. |
| • | The PCM records the operating conditions at the time the diagnostic fails. The Freeze Frame and Failure Records buffers stores this information. |
| • | A history DTC is stored. |
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, the connector, or the terminal are damaged, replace the entire oxygen sensor assembly. Do not attempt to repair the wiring, connector or terminals. In order for the sensor to function properly, the rear HO2S 2 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 performance of the oxygen sensor.
A poor connection, rubbed through wire insulation or a wire broken inside the insulation may cause an intermittent.
Check for the following conditions:
| • | A poor connection or damaged harness - Inspect the PCM harness for the following condition: |
| - | Open in the rear HO2S high circuit |
| - | Improper mating |
| - | Broken locks |
| - | Improperly formed or damaged terminals |
| - | Poor terminal to wire connection |
| - | Damaged harness. |
| • | An intermittent test - Observe the rear HO2S 2 on the scan tool while moving the 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
The numbers below refer to the step numbers on the diagnostic table.
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The OBD System Check prompts the technician to complete some basic checks and store the Freeze Frame Data and the Failure Records on the scan tool if applicable. This creates an electronic copy of the data taken when the fault occurred. This information on the scan tool can be referred to later.
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Disconnecting the rear HO2S 2 and jumpering the rear HO2S low and high circuits to ground will determine if the PCM , wiring, or the rear HO2S 2 is at fault.
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Before replacing the PCM, check the terminals for improper mating, broken locks, or physical damage to the wiring harness. Reprogram the replacement PCM. 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? | -- | |||
2 |
Does the scan tool display a HO2S 2 voltage between the specified value? | 80° C (176° F) 1200 RPM 425 mV to 456 mV (0.425 V to 0.456 V) | ||
3 |
Does the scan tool display the HO2S 2 voltage steady around the specified value? | 425 mV to 456 mV (0.425 V to 0.456 V) | ||
Does the scan tool display the HO2S 2 voltage below the specified voltage? | 100 mV (0.10 V) | |||
5 |
Was a repair necessary? | -- | ||
6 |
Does the test lamp illuminate? | -- | ||
7 | Replace the HO2S 2. Refer to Heated Oxygen Sensor Replacement . Is the action complete? | -- | -- | |
8 |
Was a repair necessary? | -- | ||
9 | Repair the open in the HO2S 2 low circuit. Refer to Wiring Repairs in Engine Electrical. Is the action complete? | -- | -- | |
Replace the PCM. Refer to Powertrain Control Module Replacement/Programming . Is the action complete? | -- | -- | ||
11 |
Does the scan tool indicate that this diagnostic ran and passed? | 90°-95° C | ||
12 | Check if any additional DTCs are set. Are any DTCs displayed that have not been diagnosed? | -- | Go to the Applicable DTC Table | System OK |
