Refer to Engine Controls Schematics .
Circuit Description
The heated oxygen sensor 2 (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 powertrain control module (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 Running the DTC
| • | Engine run time is less than 4.25 minutes. |
| • | Start up coolant temperature and start up IAT are less than 45°C (113°F). |
| • | Difference between ECT and IAT is less than 7°C (45°F). |
| • | Battery voltage between 11.6 volts and 16.0 volts. |
| • | Average flow prior to activity must be less than 20 g/sec. |
| • | HO2S voltage at start up must be between 395 mV and 491 mV. |
| • | Fuel ethanol composition is less than 15 percent. |
| • | None of the following DTCs set: |
| 105, 107, 108, 112, 113, 117, 118, 122, 123, 169, 171, 172, 178, 179, 201, 202, 203, 204, 300, 336, 440, 446, 452, 453, 506, 507, 601, 602, and 1441. |
Conditions for Setting the DTC
HO2S 2 voltage changes less than 150 mV from the bias voltage (447mv), in a calculated amount of time.
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 is stored. |
Conditions for Clearing the MIL/DTC
| • | The 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. |
| • | A scan tool can clear the DTCs. |
Diagnostic Aids
An intermittent could be the result of the following conditions:
| • | Poor electrical connection |
| • | Moisture in the connectors or wiring |
| • | Rubbed through wire insulation |
| • | Broken wire inside of the insulation |
Inspect for a poor electrical connection or a damaged harness. Inspect the harness electrical connectors for the following conditions:
| • | Improper mating |
| • | Broken locks |
| • | Improperly formed electrical connectors |
| • | Damaged terminals |
| • | A poor terminal to wire connection |
| • | A damaged harness |
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 degraded 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.
Test Description
The numbers below refer to the step numbers on the diagnostic table.
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As the heater warms the oxygen sensor to operating temperature, the HO2S will output a voltage in relation to the amount of oxygen in the exhaust. With the ignition ON and the engine OFF, the exhaust usually contains a high oxygen content. With the engine OFF the HO2S voltage will usually decrease from the initial, or bias, voltage due to the high oxygen content.
-
This step checks for proper HO2S heater ignition positive voltage and ground supply.
-
This step checks for proper PCM and signal circuit operation.
Step | Action | Values | Yes | No | ||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
1 | Did you perform the Powertrain On-Board Diagnostic (OBD) System Check? | -- | ||||||||||
|
Important: The HO2S must be cool before proceeding with a diagnosis. The ignition must remain OFF for at least one-half hour before proceeding with a diagnosis.
Does the HO2S voltage increase or decrease from the initial voltage by at least the value specified? | 150 mV | |||||||||||
3 | The condition that set this DTC is not present. This DTC may have been set by one of the following conditions:
Repair any of the above conditions as necessary. Refer to Wiring Repairs or Connector Repairs in Wiring Systems. Did you find a condition? | -- | Go to Diagnostic Aids | |||||||||
Is the test lamp ON? | -- | |||||||||||
Is the HO2S voltage less than the specified value? | 20 mV | |||||||||||
6 |
Is the test lamp illuminated? | -- | ||||||||||
7 |
Is the resistance less than the specified value? | 5 ohms | ||||||||||
8 | Replace the HO2S. Refer to Heated Oxygen Sensor Replacement . Is the action complete? | -- | -- | |||||||||
9 | Repair the open HO2S heater ground circuit. Refer to Wiring Repairs in Wiring Systems. Is the action complete? | -- | -- | |||||||||
10 |
Is the action complete? | -- | -- | |||||||||
11 | Repair the circuit that measured high resistance. Refer to Wiring Repairs in Wiring Systems. Is the action complete? | -- | -- | |||||||||
12 |
Did you find a condition? | -- | ||||||||||
13 |
Important: The replacement PCM must be programmed. Replace the PCM. Refer to Powertrain Control Module Replacement/Programming . Is the action complete? | -- | -- | |||||||||
14 |
Important: The HO2S must be cool before proceeding with a diagnosis. The ignition must remain OFF for at least one-half hour before proceeding with a diagnosis.
Does the HO2S voltage increase or decrease from the initial voltage by at least the value specified? | 150 mV | ||||||||||
15 | Does the scan tool display any additional undiagnosed DTCs? | -- | Go to applicable DTC table | System OK |
