P0141

Heated Oxygen Sensor 2 (HO2S 2) Circuit:

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 PCM can then calculate the catalytic converter's ability to convert exhaust emissions effectively. The rear 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 voltage changes less than 148 mV in 100 to 190 seconds
- The Engine Coolant Temperature (ECT)is less than 40°C (104°F)
- The Intake Air Temperature (IAT)is less than 40°C (104°F)
- The temperature difference between the ECT sensor and the IAT is less than 7°C (45°F)
- The Throttle Position angle is greater than 18% for greater than 5 seconds

Action Taken When the DTC Set
- The Malfunction Indicator Lamp (MIL) will illuminate after two consecutive ignition cycles in which the diagnostic runs with the fault active.
- The PCM will record operating conditions at the time the diagnostic fails. This information will be stored 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 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.
- DTCs can be cleared by using a scan tool.

NOTE: 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 sensor to function properly, The rear HO2S 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 oxygen sensor performance.

Diagnostic Aids
Check for:
- A poor connection or damaged harness - Inspect the harness connectors for improper mating, broken locks, improperly formed or damaged terminals, or a damaged harness.
- An intermittent may be caused by rubbed through wire insulation or a wire contacting the exhaust.

DTC P0141 - Heated Oxygen Sensor (HO2S) Heater Circuit Sensor 2:

Test Description
Numbers below refer to the step numbers on the Diagnostic Table.
1. 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.
2. With the ignition "ON," and the engine "OFF," the rear HO2S 2 voltage displayed on the scan tool should change within several minutes between 0 or 1 volt, indicating that the heater is working properly.
3. Probing terminal "D" of the rear HO2S 2 connector verifies if voltage is available to the rear HO2S 2 heater.
4. Whenever voltage is available at the connector, then the connector becomes a good voltage source to check for a ground at terminal "C".
5. Determines if voltage is not available at the rear HO2S 2 due to an open O2S fuse or open ignition feed. Whenever the fuse is open, determine the cause of the short to ground in the ignition feed circuit before replacing the fuse.