P0140

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 which indicates the oxygen storage capacity of the catalytic converter. This indicates to the PCM 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 (O2S).

Conditions for Setting the DTC
- The rear HO2S 2 remains between 425 mV and 460 mV 42 seconds
- The engine has been running for greater than 30 seconds
- The Throttle Position angle is between 4% and 55%
- The engine coolant temperature is greater than 70°C (158°F)
- The vehicle is in "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) 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 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 oxygen sensor performance.
An intermittent may be caused by a poor connection, rubbed through wire insulation or a wire broken inside the insulation.

Diagnostic Aids
Check for:
- Poor connection or damaged harness - Inspect the PCM harness for open in the rear HO2S high circuit, improper mating, broken locks, improperly formed or damaged terminals, poor terminal to wire connection and damaged harness.
- 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.

DTC P0140 - Heated Oxygen Sensor (HO2S) Circuit Insufficient Activity Sensor 2 (1 Of 2):

DTC P0140 - Heated Oxygen Sensor (HO2S) Circuit Insufficient Activity Sensor 2 (2 Of 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.
4. 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.
10. Before replacing the PCM, check terminals for improper mating, broken locks, or physical damage to the wiring harness. Replacement PCM must be reprogrammed. Refer to the latest Techline information for programming procedures.