DTC P0140 or P0160. Pontiac GTO 2004

For 1990-2009 cars only

Makes 🢒 Pontiac 🢒 2004 🢒 GTO 🢒 Engine 🢒 Engine Controls - 5.7L 🢒 DTC P0140 or P0160

Circuit Description

The powertrain control module (PCM) supplies a voltage of about 450 mV between the HO2S high and low signal circuits. The oxygen sensor varies the voltage over a range from about 1,000 mV when the exhaust is rich, down through about 10 mV when the exhaust is lean.

The PCM monitors and stores the heated oxygen sensor (HO2S) voltage information. The PCM evaluates the HO2S voltage samples in order to determine the amount of time the HO2S voltage was out of range. The PCM compares the stored HO2S voltage samples taken within each sample period and determines if the majority of the samples are out of the operating range.

The PCM 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.

DTC Descriptors

This diagnostic procedure supports the following DTCs.

•	DTC P0140 HO2S Circuit Insufficient Activity Bank 1 Sensor 2

•	DTC P0160 HO2S Circuit Insufficient Activity Bank 2 Sensor 2

Conditions for Running the DTC

•	DTCs P0101, P0102, P0103, P0106, P0107, P0108, P0112, P0113, P0116, P0117, P0118, P0121, P0122, P0123, P0125, P0128, P0141, P0161, P0200, P0300, P0443, P0496, P1111, P1112, P1114, P1115, P1121, or P1122 are not set.

•	The ignition 1 signal is between 10-18 volts.

•	The engine run time is more than 300 seconds.

•	The loop status is CLOSED.

•	The intrusive tests are not in progress.

•	DTC P0140 and P0160 run once per ignition cycle when the above conditions are met.

Conditions for Setting the DTC

The HO2S signal voltage is steady between 410-490 mV for 150 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.

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

Test Description

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

Before you perform this test, the engine must be at the normal operating temperature.

The Freeze Frame/Failure Records may help to locate an intermittent condition. If you cannot duplicate the DTC, the information in the Freeze Frame/Failure Records can help to determine how many miles have occurred since the DTC set. The Fail Counter and the Pass Counter can also determine how many ignition cycles have occurred since the diagnostic reported a pass and/or a fail. In order to isolate when the DTC failed, operate the vehicle within the same Freeze Frame conditions that the PCM recorded. These conditions include the RPM, the vehicle load, the vehicle speed, and the temperature.

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

This step verifies whether the HO2S low signal circuit from the PCM is OK.

This step verifies whether the HO2S low signal circuit from the PCM is OK. A voltage indicates that the PCM and wiring are OK.

Disconnecting the PCM allows using a DMM in order to test the circuit continuity. This procedure helps to locate a circuit that is open or shorted.

Step

Action

Values

Yes

Schematic Reference: Engine Controls Schematics

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

Did you perform the Diagnostic System Check-Engine Controls?

Go to Step 2

Go to Diagnostic System Check - Engine Controls

Important:

•	Before you proceed with this DTC, inspect the HO2S for being secure. A loose sensor can cause this DTC to set.

•	If the HO2S heater current is not between 0.25-3.125 Amps, refer to DTC P0135, P0141, P0155, or P0161 .

Install a scan tool.
Idle the engine at the normal operating temperature.
Change the throttle position more than 5 percent within 1 second, 6 times.
Use a scan tool in order to observe the HO2S voltage.

Does the scan tool indicate that the HO2S voltage is outside the specified range?

410-490 mV

Go to Step 3

Go to Step 4

Observe the Freeze Frame/Failure Records data for this DTC.
Turn OFF the ignition for 30 seconds.
Start the engine.
Operate the vehicle within the Conditions for Running the as specified in the supporting text or as close to the Freeze Frame/Failure Records data that you observed.

Does the DTC fail this ignition?

Go to Step 4

Go to Intermittent Conditions

Turn ON the ignition, with the engine OFF.
Disconnect the HO2S.
Jumper the HO2S high signal circuit to a known good ground.
Jumper the HO2S low signal circuit to a known good ground.
Use a scan tool in order to observe the HO2S voltage.

Is the HO2S voltage below the specified value?

200 mV

Go to Step 8

Go to Step 5

Remove both jumper wires.
Measure the voltage from the HO2S low signal circuit to a battery ground using the DMM.

Does the DMM indicate near the specified value?

5 V

Go to Step 6

Go to Step 7

Turn OFF the ignition.
Disconnect the PCM connector C1. Refer to Powertrain Control Module Replacement .
Test the continuity of the HO2S high signal circuit. Refer to Testing for Continuity in Wiring Systems.
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

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

Did you find and correct the condition?

Go to Step 12

Go to Step 10

Inspect for a poor connection at the HO2S. Refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems.
If you find a poor connection, repair the connection 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

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

Did you complete the replacement?

Go to Step 12

Inspect for a poor connection at the PCM. Refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems.
If you find a poor connection, repair the connection 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

Replace the PCM. Refer to Powertrain Control Module Replacement .

Did you complete the replacement?

Go to Step 12

Use a scan tool in order to clear the DTCs.
Turn OFF the ignition for 30 seconds.
Start the engine.
Operate the vehicle within the Conditions for Running the DTC as specified in the supporting text.

Does the DTC run and pass?

Go to Step 13

Go to Step 2

With a scan tool, observe the stored information, Capture Info.

Does the scan tool display any DTCs that you have not diagnosed?

Go to Diagnostic Trouble Code (DTC) List

System OK