P0140 or P0160 (Federal W/RPO L35)

CIRCUIT DESCRIPTION
The heated oxygen sensor (HO2S) is a sensor designed to create a voltage relative to the oxygen content in the engine exhaust stream. The control module supplies the HO2S with signal high and low circuits. Ignition voltage and ground are supplied to the HO2S heater by independent circuits. The oxygen content of the exhaust indicates when the engine is operating lean or rich. When the HO2S detects that the engine is operating rich, the signal voltage is high, and decreases the signal voltage as the engine runs leaner. This oscillation above and below the bias voltage, sometimes referred to as activity or switching, can be monitored with the HO2S signal voltage.

The HO2S contains a heater that is necessary in order to quickly warm the sensor to operating temperature. The heater also maintains the operating temperature during extended idle conditions. The HO2S needs to be at a high temperature in order to produce a voltage. When the HO2S reaches operating temperature, the control module monitors the HO2S bias, or reference, voltage. The control module also monitors the HO2S signal voltage for Closed Loop fuel control. During normal Closed Loop fuel control operation, the control module will add fuel, or enrich the mixture, when the HO2S detects a lean exhaust content. The control module will subtract fuel, or lean out the mixture when the HO2S detects a rich exhaust condition.

This DTC monitors the HO2S voltage and detects if the voltage goes out of the bias range. If the (PCM) does not detect the voltage went out of the bias range, a DTC sets

CONDITIONS FOR RUNNING THE DTC
^ DTCs P0101, P0102, P0103, P0106, P0107, P0108, P0112, P0113, P0116, P0117, P0118, P0121, P0122, P0123, P0200, P0300, P0401, P0404, P0405, P0440, P0442, P0446, P0452, P0453, P1404, or P1441 are not set.
^ The engine run time is more than 409 seconds.
^ The loop status is closed.
^ The ignition 1 signal is between 9-18 volts.
^ Intrusive tests are not in progress.
^ Scan tool output controls are not active.

CONDITIONS FOR SETTING THE DTC
^ The HO2S signal voltage is steady between 400-475 mV for 150 seconds.
^ The throttle position (TP) changes more than 5 percent within 1 second, 6 times.

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.
^ Clear the MIL and the DTC with a scan tool.

DIAGNOSTIC AIDS

IMPORTANT: Before you service the PCM, remove any debris from the PCM connector surfaces. Inspect the PCM connector gaskets when diagnosing or replacing the PCM. Ensure that the gaskets are installed correctly. The gaskets prevent water intrusion into the PCM.

^ An oxygen supply inside the HO2S is necessary for proper operation. The HO2S wires provides the supply of oxygen. Inspect the HO2S wires and connections for breaks or contamination. Refer to Heated Oxygen Sensor (HO2S) Wiring Repairs in Diagnostic Aids.
^ For an intermittent condition, refer to Symptoms - Computers and Controls Systems. Symptom Related Diagnostic Procedures

TEST DESCRIPTION

DTC P0140 Or P0160 (Federal W/RPO L35) - Steps 1-7:

DTC P0140 Or P0160 (Federal W/RPO L35) - Steps 8-17:

DTC P0140 Or P0160 (Federal W/RPO LU35) - Steps 18-22:

The numbers below refer to the step numbers on the diagnostic table.
2. After the ignition is turned ON, the HO2S heater heats up causing the HO2S signal voltage to either increase or decrease. This indicates that the HO2S heater is OK.
3. If the HO2S voltage is varying outside the specified range, the condition is not present.
5. If the voltage is below the specified value, the high signal circuit, the low signal circuit, and the PCM are OK.
6. If the voltage is above the specified value, the low signal circuit is OK.
12. The opposite bank HO2S must be disconnected to isolate a short to ground in the HO2S heater ignition 1 voltage circuit.
14. Resistance within the specified range indicates the HO2S heater is OK.

For a description of the RPO Code(s) shown in this article or any of the images therein, refer to the RPO Code List found at Vehicle/Application ID". RPO Codes