GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Chevrolet 🢒 2003 🢒 Corvette 🢒 Engine 🢒 Engine Controls - 5.7L 🢒 DTC P0140 or P0160

Circuit Description

Heated oxygen sensors (HO2S) are used for fuel control and post catalyst monitoring. Each HO2S compares the oxygen content of the surrounding air with the oxygen content in the exhaust stream. The HO2S must reach operating temperature to provide an accurate voltage signal. Heating elements inside the HO2S minimize the time required for the sensors to reach operating temperature. The powertrain control module (PCM) supplies the HO2S with a reference, or bias, voltage of about 450 mV. When the engine is first started the PCM operates in open loop, ignoring the HO2S voltage signal . Once the HO2S reaches operating temperature and closed loop is achieved, the HO2S generates a voltage within a range of 0-1,000 mV that fluctuates above and below bias voltage. High HO2S voltage indicates a rich exhaust stream; low HO2S voltage indicates a lean exhaust stream.

This diagnostic will only run once per ignition cycle. If the PCM detects an HO2S voltage that remains within the bias voltage range, DTC P0140 or P0160 sets.

Conditions for Running the DTC
    • DTCs P0101, P0102, P0103, P0106, P0107, P0108, P0112, P0113, P0116, P0117, P0118, P0135, P0141, P0155, P0161, P0200, P0300, P0410, P0440, P0442, P0446, P0452, P0453, P1120, P1125, P1220, P1221, P1221, P1258, P1415, P1416, P1441, P1514, P1515, P1516, P1517, or P1518 are not set.
    • The Engine Run Time parameter is more than 409 seconds.
    • The Ignition 1 Signal parameter is between 9-18 volts.
    • The Loop Status parameter is Closed.

Conditions for Setting the DTC
    • The affected HO2S voltage parameter is between 410-490 mV for 150 seconds.
    • The TP indicated angle parameter 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.

Test Description

The numbers below refer to the step numbers on the diagnostic table.

  1. The engine must be at the normal operating temperature before you perform this test.

    2.

  2. If the scan tool indicates that the HO2S voltage goes below 200 mV, this indicates the HO2S circuits and PCM are OK.

    3.

  3. This step verifies whether the low signal circuit from the PCM is OK. A voltage indicates that the PCM and the wiring are OK.

    4.

  4. This step verifies whether the signal circuit from the PCM is OK.

    5.

  5. Disconnecting the PCM allows you to use a DMM in order to test the circuit continuity. This procedure helps to locate an open or shorted circuit.

Step

Action

Values

Yes

No

Schematic Reference: Engine Controls Schematics

Connector End View Reference: Powertrain Control Module Connector End Views or Engine Controls Connector End Views

1

Did you perform the Diagnostic System Check-Engine Controls?

--

Go to Step 2

Go to Diagnostic System Check - Engine Controls

2

Important: Inspect the HO2S for being secure before proceeding with this DTC. A loose sensor could cause this DTC to set.

  1. Install a scan tool.
  2. Start the engine and idle the engine at the normal operating temperature.
  3. Change the throttle position more than 5 percent within 1 second, 6 times.
  4. Observe the HO2S voltage with a scan tool.

Is the HO2S voltage outside the specified range?

410-490 mV

Go to Step 3

Go to Step 4

3
  1. Observe the Freeze Frame/Failure Records for this DTC.
  2. Turn OFF the ignition for 30 seconds.
  3. Start the engine.
  4. Operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records.

Did the DTC fail this ignition?

--

Go to Step  4

Go to Intermittent Conditions

4

  1. Turn ON the ignition, with the engine OFF.
  2. Disconnect the HO2S.
  3. Jumper the HO2S high signal circuit to a known good ground.
  4. Jumper the HO2S low signal circuit to a known good ground.
  5. Observe the HO2S voltage with a scan tool.

Is the HO2S voltage below the specified value?

200 mV

Go to Step 8

Go to Step 5

5

  1. Remove both jumper wires.
  2. Use the DMM in order to measure the voltage from the HO2S low signal circuit to a battery ground.

Is the voltage near the specified value?

5 V

Go to Step 6

Go to Step 7

6

  1. Turn OFF the ignition.
  2. Disconnect the PCM connector C1. Refer to Powertrain Control Module Replacement .
  3. Test for continuity of the HO2S high signal circuit. Refer to Testing for Continuity in Wiring Systems.
  4. If no continuity is indicated on the DMM, repair the open circuit. Refer to Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 12

Go to Step 10

7

  1. Turn OFF the ignition.
  2. Disconnect the PCM connector C1. Refer to Powertrain Control Module Replacement .
  3. Test for continuity of the HO2S low signal circuit. Refer to Testing for Continuity in Wiring Systems.
  4. If no continuity is indicated on the DMM, repair the open or the faulty connection. Refer to Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 12

Go to Step 10

8
  1. Inspect the HO2S circuits for a faulty connection at the HO2S harness connector. Refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems.
  2. If you find a faulty connection, replace or repair the terminal as necessary. Refer to Repairing Connector Terminals in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 12

Go to Step 9

9

Replace the affected HO2S. Refer to Heated Oxygen Sensor Replacement - Bank 1 Sensor 2 or Heated Oxygen Sensor Replacement - Bank 2 Sensor 2 .

Did you complete the replacement?

--

Go to Step 12

--

10
  1. Inspect the HO2S circuits for a faulty connection at the PCM. Refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems.
  2. If you find a faulty connection, replace or repair the terminal as necessary. Refer to Repairing Connector Terminals in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 12

Go to Step 11

11

Replace the PCM. Refer to Powertrain Control Module Replacement .

Did you complete the replacement?

--

Go to Step 12

--

12
  1. Clear the DTCs with a scan tool.
  2. Turn OFF the ignition for 30 seconds.
  3. Start the engine.
  4. Operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records.

Did the DTC fail this ignition?

--

Go to Step 2

Go to Step 13

13

Observe the Capture Info with the scan tool.

Are there any DTCs that have not been diagnosed?

--

Go to Diagnostic Trouble Code (DTC) List

System OK