P0140

Diagnostic Chart:

Wiring Diagram:

CIRCUIT DESCRIPTION

In order to control the 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 Rear Heated Oxygen Sensor (HO2S 2), 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 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 (O2S 1).

If the oxygen sensor pigtail wiring, connector, or the terminal are damaged, replace the entire oxygen sensor assembly. Do not attempt to repair the wiring, connector, or the terminals. The sensor must have a clean air reference in order for the sensor to function properly. This clean air reference is obtained by way of the oxygen sensor wire(s). Any attempt to repair the wires, connectors, or the terminals could result in the obstruction of the air reference and degrade oxygen sensor performance. Refer to Heated Oxygen Sensor (O2S) Repair.

CONDITIONS FOR SETTING THE DTC

^ DTCs P0106, P0107, P0108, P011 2, P0113, P0117, P0118, P0121, P0122, P0123, P0171, P0200, P0300, P0301, P0302, P0303, P0304, P0341, P0404, P0506, P0507, P0601, P0602 not set.

^ Air flow is greater than 5.5 grams per second.

^ Engine Coolant Temperature (ECT) is greater than 40°C (104°F).

^ Throttle Position (TP) is between 4% and 56%.

^ 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 DTC will clear after 40 consecutive warm up cycles without a fault.

^ The MIL/DTC(s) can be cleared by using the scan tool.

DIAGNOSTIC AIDS

An intermittent could be the result of a poor connection, a rubbed through wire insulation, or a broken wire inside of the insulation.

Check for the following conditions:

^ A poor connection or a damaged harness-Inspect the PCM harness for an open in the HO2S 2 signal circuit. Check for the following conditions: Refer to Heated Oxygen Sensor (O2S) Replacement:

- 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 connectors and the wiring harness with the key ON. If the malfunction is induced, the HO2S 2 display will change. This test should help isolate the location of the malfunction.

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 failure or an intermittent condition.

4. Disconnecting the HO2S 2 and jumpering 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 connection or the PCM is malfunctioning.

10. Reprogram the replacement PCM and perform the crankshaft position system variation learning procedure. Refer to the latest Techline information for PCM programming and Crankshaft Position (CKP) System Variation Learn Procedure for the crankshaft position system variation learning procedure.