P0140

P0140 O2 Bank 1 Sensor 2 No Activity




Circuit Description
In order to control emissions, a catalytic converter is used to convert harmful emissions into harmless water vapor and carbon dioxide.

The powertrain control module (PCM)/engine control module (ECM) has the ability to monitor this process by using a Heated Oxygen Sensor (HO2S). The HO2S, located in the exhaust stream past the catalytic converter, produces an output signal which indicates the storage capacity of the catalyst: this in turn indicates the catalyst's ability to convert exhaust emissions effectively. If the catalyst is functioning properly, the HO2S signal will be far less active than the signal produced by the Oxygen Sensor (O2S).

If the HO2S pigtail wiring, connector or terminal are damaged, the entire HO2S assembly must be replaced. Do not attempt to repair the wiring, connector or terminals. In order for the sensor to function properly, it must have a clean air reference provided to it. This clean air reference is obtained by way of the HO2S wire(s). Any attempt to repair the wires, connector or terminals could result in the obstruction of the air reference and degrade HO2S 2 performance.

Conditions for Setting the DTC
- HO2S is between 0.422 and 0.478 volts.
- Engine run time is greater than 60 seconds.
- Closed loop stoichiometry.
- No related malfunctions (see P0131).

Action Taken When the DTC Sets
- The Malfunction Indicator Lamp (MIL) will illuminate.
- The PCM/ECM 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 Diagnostic Trouble Code (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.
- DTC(s) can be cleared by using the scan tool.

Diagnostic Aids
An intermittent may be caused by rubbed through wire insulation or a wire contacting the exhaust.
Check for the following conditions:
- Poor connection or damaged harness Inspect the harness for a short to ground in the sensor signal circuit. Ensure that the HO2S pigtail is not contacting the exhaust. Check for the following conditions:
- Improper mating
- Broken locks
- Improperly formed
- Damaged terminals
- Poor terminal-to-wire connection
- Damaged harness

- Intermittent test - Observe the HO2S on scan tool while moving related connections and wiring harness with the ignition ON. If the failure is induced, the HO2S display will change. This may help isolate the location of the malfunction.

Step 1 - 4:

Step 5 - 12:

Test Description
Number(s) below refer to the step number(s) on the Diagnostic Table.
1. The On-Board Diagnostic (OBD II) System Check prompts the technician to complete some basic checks and store the freeze frame and failure records data on the scan tool if applicable. This creates an electronic copy of the data taken when the malfunction occurred. The information is then stored on the scan tool for later reference.
2. This step determines if DTC P0140 is the result of a hard failure or an intermittent condition.
4. Disconnecting the HO2S and jumpering the sensor signal circuit and the sensor low circuit to ground will determine if the PCM/ECM or wiring or HO2S is malfunctioning.
6. Determines which circuit the malfunction is in. If the sensor signal circuit and the sensor low circuit are OK, then the PCM/ECM connection or PCM/ECM is malfunctioning.
10. The replacement PCM/ECM must be reprogrammed. Refer to the latest Techline procedure for PCM/ECM reprogramming.