P0140

CIRCUIT DESCRIPTION
In order to control emissions, a catalytic converter converts any harmful exhaust emissions into harmless water vapor and carbon dioxide.

The Powertrain Control Module (PCM) has the capability to monitor this process by using a rear Heated Oxygen Sensor (HO2S) 2. The 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 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 (O2S) 1.

Obstruction of the air reference and degraded HO2S 2 performance could result from 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 wires.

CONDITIONS FOR RUNNING THE DTC
^ DTCs P0105, P0107, P0108, P0112, P0113, P0117, P0118, P0122, P0123, P0171, P0201-P0204, P0300, P0301-P0304, P0335, P0440, P0442, P0446, P0506, P0507, P0601, P0602, or P1441 are not set.
^ The engine coolant temperature is greater than 70°C (158°F).
^ The battery voltage is greater than 10 volts.
^ The fuel level is greater than 10 percent.
^ The engine run time is greater than 30 seconds.
^ The air flow is more than 5.5 g/s.
^ The Throttle Position (TP) is between 8-56 percent.
^ The Manifold Absolute Pressure (MAP) is greater than 25 kPa.
^ The engine is operating in closed loop.

CONDITIONS FOR SETTING THE DTC
HO2S 2 remains between 425-460 mV for 125 seconds.

ACTION TAKEN WHEN THE DTC SETS
^ The control module illuminates the Malfunction Indicator Lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
^ The control module records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the control module stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the control module records the operating conditions at the time of the failure. The control module writes the operating conditions to the Freeze Frame and updates the Failure Records.

CONDITIONS FOR CLEARING THE MIL/DTC
^ The control module turns OFF the Malfunction Indicator Lamp (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail.
^ A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
^ A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
^ Use a scan tool in order to clear the MIL and the DTC.

DIAGNOSTIC AIDS
An intermittent could be the result of the following conditions:
^ A faulty electrical connection
^ Moisture in the electrical connector or connector wiring
^ Rubbed-through wire insulation
^ A broken wire inside the insulation

Check for the following conditions:
^ A faulty 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 faulty terminal-to-wire connection
- A damaged harness
^ An 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.

Obstruction of the air reference and degraded 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 wires.

TEST DESCRIPTION

Steps 1-9:

Steps 10-14:

The numbers below refer to the step numbers on the diagnostic table.
2. When the system is operating correctly the HO2S voltage should toggle above and below the specified voltage.
5. This step checks the PCM and the high signal circuits between the PCM and the HO2S connector for proper voltage.
6. The specified value is what is measured on a correctly operating system.
13. This step checks for proper circuit resistance between the HO2S low signal circuit and PCM ground.