P0140

CIRCUIT DESCRIPTION
The Heated Oxygen Sensor 2 (HO2S 2), located in the exhaust stream past the catalytic converter, produces an output signal relative to the oxygen storage capacity of the catalytic converter. The Powertrain Control Module (PCM) can then determine the ability of the catalytic converter to convert the exhaust emissions effectively. The HO2S 2 signal will be far less active than the signal produced by the front oxygen sensor 1 (O2S 1).

CONDITIONS FOR RUNNING THE DTC
^ DTCs P0105, P0107, P0108, P0112, P0113, P0117, P0118, P0122, P0123, P0169, P0171, P0172, P0178, P0201-P0204, P0300, P0301-P0304, P0336, P0440, P0446, P0452, P0453, P0506, P0507, P0601, P0602, or P1441 are not set.
^ The air flow is more than 5.5 grams per second for 140 seconds.
^ The Engine Coolant Temperature (ECT) is more than 70°C (158°F).
^ The above conditions are met for 70 seconds.
^ The engine run time is more than 30 seconds in Closed Loop.
^ The throttle position (TP) is between 8-56 percent.
^ The Manifold Absolute Pressure (MAP) is greater than 25 kPa.
^ The fuel level is greater than 10 percent.
^ The battery voltage is greater than 10 volts.

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

IMPORTANT: Never solder the HO2S wires. For proper wire and connection repairs, refer to Wiring Repairs or Connector Repairs in Diagrams.

Inspect for exhaust system leaks upstream of the suspect HO2S. The leak may be very small and typically be within 30.5 cm (12 inches) of the suspect HO2S. Refer to Exhaust Leakage in Exhaust System. Testing and Inspection

A Malfunctioning HO2S Heater or Heater Circuit With the ignition ON and the engine OFF, the HO2S voltage displayed on a scan tool should gradually drop to below 0.150 volts, indicating that the heater works properly. If not, disconnect the HO2S and connect a test lamp between the terminals C and D. If the test lamp does not light, repair the open in the HO2S ground circuit or the HO2S ignition 1 voltage circuit. If the test lamp lights, replace the HO2S.

The Intermittent Test
Use a scan tool in order to monitor this HO2S signal voltage. Move the related connectors and the wiring harness with a warm engine running at part throttle in Closed Loop. If the failure is induced, the HO2S signal voltage reading changes from the normal fluctuating voltage (above 600 mV and below 300 mV) to a fixed value around 450 mV. This may help to isolate the location of the malfunction.

An intermittent may be caused by any of the following conditions:
^ A poor connection
^ Rubbed through wire insulation
^ A broken wire inside the insulation Thoroughly check any circuitry that is suspected of causing the intermittent complaint. Refer to Testing for Intermittent and Poor Connections in Diagrams.

If a repair is necessary, refer to Wiring Repairs or Connector Repairs in Diagrams.

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 1 voltage should toggle above and below the specified values.
5. The specified value is what is measured on a correctly operating system.
6. The specified value is what is measured on a correctly operating system.
12. The replacement PCM must be reprogrammed and the crankshaft position system variation learn procedure must be performed.