P0140
Circuit Description
In order to control emissions, a catalytic converter converts any harmful exhaust emissions into harmless water vapor and carbon dioxide.
The PCM has the capability to monitor this process by using a Rear Heated Oxygen Sensor (HO2S 2). The HO2S 2 sensor, 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 catalysts ability to convert the exhaust emissions effectively. If the catalyst is functioning properly, the HO2S 2 signal will be far less active than the signal produced by the front Oxygen Sensor (02S 1).
Replace the entire HO2S 2 sensor assembly (Do not attempt to repair the HO2S 2) if the following conditions exist:
^ Damaged wiring
^ Damaged electrical connector
^ Damaged terminal(s)
Obstruction of the air reference and degrade 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 sensor to function properly. This clean air reference is obtained by way of the HO2S 2 wire(s).
Conditions for Running the DTC
^ DTCs P0105, P0107, P0108, P0112, P0113, P0117, P0118, P0122, P0123, P0171, P0200, P0300, P0301, P0302, P0303, P0304, P0335, P0440, P0442, P0446, P0506, P0507, P0601, P0602, or P1441 not set.
^ Air flow is more than 5.5 grams per second.
^ Engine Coolant Temperature (ECT) is more than 40°C (104°F).
^ Throttle Position (TP) is between 4% and 56%.
Conditions For Setting The DTC
HO2S 2 remains between 425 mV and 460 mV for 125 seconds.
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 stores.
^ The coolant fan turns ON.
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 DIC will clear after 40 consecutive warm up cycles without a fault.
^ The MIL/DTCs can be cleared by using the scan tool.
Diagnostic Aids
An intermittent could be the result of the following conditions:
^ Poor electrical connection
^ Moisture in the electrical connector/wiring
^ Rubbed through wire insulation
^ Broken wire inside of the insulation Check for the following conditions:
^ A poor electrical connection or a damaged harness-Inspect the PCM harness for an open in the HO2S 2 signal circuit. Check for the following conditions:
- Improper mating
- Broken locks
- Improperly formed connectors
- Damaged terminals
- A poor terminal to wire connection
- A damaged harness
^ Intermittent test-Observe the HO2S 2 on the scan tool while moving the related electrical connectors and the wiring harness with the ignition switch ON. If the malfunction is induced, the HO2S 2 display will change. This test should help isolate the location of the malfunction.
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 terminal(s)
Obstruction of the air reference and degrade 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 wire(s).
Test Description
The number(s) below refer(s) to the step number(s) on the Diagnostic Table.
1. The Powertrain OBD System Check prompts you to complete some of the basic checks and to store the freeze frame and failure records data on the scan tool if applicable. This creates an electronic copy of the data captured when the malfunction occurred. The scan tool stores this data for later reference.
2. This step determines if DTC P0140 is the result of a hard malfunction or an intermittent condition.
4. Disconnecting the HO2S 2 and connecting a jumper wire between the HO2S 2 signal circuit and the HO2S 2 low circuit to ground, will determine if the PCM or wiring or HO2S 2 is malfunctioning.
6. This step determines which circuit the malfunction is in. If the HO2S 2 signal circuit and the HO2S 2 low circuit are OK, this is an indication that the PCM electrical connection or the PCM is malfunctioning.
10. Reprogram the replacement PCM and perform the crankshaft position system variation learn procedure. Refer to the latest Techline information for PCM programming and CKP System Variation Learn Procedure for the crankshaft position system variation learn procedure.