Circuit Description
The heated oxygen sensor (HO2 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
| • | No active MAP DTCs |
| • | No active IAT DTCs |
| • | No active ECT DTCs |
| • | No active TP DTCs |
| • | No active fuel trim DTCs |
| • | No active injector control DTCs |
| • | No active misfire DTCs |
| • | No active CKP DTCs |
| • | No active EVAP DTCs |
| • | No active IAC DTCs |
| • | No active PCM memory DTCs |
| • | The engine run time is less than 400 seconds |
| • | Engine coolant temperature (ECT) less than 45°C (113°F) |
| • | Intake air temperature (IAT) less than 45°C (113°F) |
| • | Difference between ECT and IAT is less than 7°C (13°F) |
| • | The battery voltage is between 11.6 volts and 16 volts |
| • | The average air flow prior to activity is less than 20 grams per second |
Conditions for Setting the DTC
HO2S 2 voltage increases less than 148 mV within a predetermined time after a cold start.
Action Taken When the DTC Sets
| • | The control module illuminates the malfunction indicator lamp (MIL) if a failure is detected during 2 consecutive key cycles. |
| • | The control module sets the DTC and records the operating conditions at the time the diagnostic failed. The failure information is stored in the scan tools Freeze Frame and Failure Records. |
Conditions for Clearing the MIL/DTC
| • | The control module turns OFF the MIL after 3 consecutive drive trips when the test has Run and Passed |
| • | A history DTC will clear if no fault conditions have been detected for 40 warm-up cycles. A warm up cycle occurs when the coolant temperature has risen 22°C (40°F) from the startup coolant temperature and the engine coolant reaches a temperature that is more than 70°C (158°F) during the same ignition cycle. |
| • | Use a scan tool to clear the DTCs. |
Diagnostic Aids
An intermittent may be the result of the following conditions:
| • | Poor electrical connection |
| • | Moisture in the connector/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 degrade HO2S 2 performance may 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:
-
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 (bias) voltage due to the high oxygen content.
-
This step tests for proper HO2S heater ignition positive voltage and ground supply.
-
This step tests for proper PCM and signal circuit operation.
-
The replacement PCM must be programmed and the Crankshaft Position System Learn procedure must be performed.
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 diagnosis. The ignition must remain OFF for at least one half hour before proceeding with diagnosis.
Does the HO2S voltage increase or decrease by the specified value? | 150 mV | |||||||||||||
3 | The condition that set this DTC is not present. This DTC may have been set by one of the following conditions:
Did you find and correct the condition? | -- | Go to Diagnostic Aids | |||||||||||
Does the test lamp illuminate? | -- | |||||||||||||
Ensure the ignition is ON with the engine OFF. Does the HO2S voltage read less than the specified value? | 20 mV | |||||||||||||
6 | Connect the test lamp between the HO2S heater ignition positive voltage circuit terminal (engine harness side) and a known good ground. Ensure the ignition is ON with the engine OFF. Does the test lamp illuminate? | -- | ||||||||||||
7 |
Does the resistance measure less than the specified value? | 5 ohms | ||||||||||||
8 | Replace the HO2S. Refer to Heated Oxygen Sensor Replacement . Did you complete the replacement? | -- | -- | |||||||||||
9 | Repair the open HO2S heater ground circuit. Refer to Wiring Repairs in Wiring Systems. Did you complete the repair? | -- | -- | |||||||||||
10 | Repair the lack of voltage on the HO2S heater ignition positive voltage circuit. Refer to Wiring Repairs in Wiring Systems. If the fuse is blown repair the short to ground on the circuit. A blown fuse or lack of voltage to the fuse may cause other DTCs or symptoms to be present. Refer to Wiring Repairs in Wiring Systems. Did you complete the repair? | -- | -- | |||||||||||
11 | Repair the circuit that measured high resistance. Refer to Wiring Repairs in Wiring Systems. Did you complete the repair? | -- | -- | |||||||||||
12 |
Did you find and correct the condition? | -- | ||||||||||||
|
Important:: The replacement PCM must be programmed. Replace the PCM. Refer to Powertrain Control Module Replacement/Programming . Did you complete the replacement? | -- | -- | ||||||||||||
14 |
Important:: The HO2S must be cool before proceeding with diagnosis. The Ignition must remain OFF for at least one half hour before proceeding with diagnosis.
Does the HO2S voltage increase or decrease by the value specified? | 150 mV | System OK |
