GPEC

P0139-O2 SENSOR 1/2 SLOW RESPONSE

For a complete wiring diagram Consult Diagrams/Electrical.

- When Monitored:
With engine run time greater than 5 minutes, coolant temperature greater than 75 C (167 F), vehicle speed greater than 97 kph (60 mph), and vehicle in decel fuel shut-off (coasting with the accelerator pedal fully released).

- Set Condition:
The O2 signal voltage does not switch quickly enough from rich to lean when the fuel is turned off during a coast with the throttle closed. Two Trip Fault. Three good trips to turn off the MIL.

Always perform the Pre-Diagnostic Troubleshooting procedure before proceeding. Initial Inspection and Diagnostic Overview.

1. EXHAUST LEAK

NOTE: A thorough exhaust leak test must be completed before removing an O2 Sensor or any other part from the exhaust system. Do not remove any parts before an exhaust leak check has been completed.

NOTE: An exhaust leak may cause downstream fuel adaptives to rail out, resulting in a false 1/1 O2 Sensor failure

Perform the diagnostic procedure for *CHECKING THE EXHAUST SYSTEM FOR LEAKS. Checking the Exhaust System For Leaks

Were any problems found?

Yes

- Go to 10

No

- Go to 2

2. DTC IS ACTIVE

NOTE: Check for contaminants that may have damaged the O2 Sensor: contaminated fuel, unapproved silicone, oil and coolant.

NOTE: It may be necessary to test drive the vehicle within the DTC monitoring conditions in order for this DTC to set.

Start the engine and allow it to reach operating temperature.

WARNING: When the engine is operating, do not stand in direct line with the fan. Do not put your hands near the pulleys, belts, or fan. Do not wear loose clothing. Failure to follow these instructions can result in personal injury or death.

With a scan tool, select View DTCs.
Is the status Active for this DTC?

Yes

- Go to 3

No

- Refer to the *CHECKING FOR AN INTERMITTENT DTC Diagnostic Procedure.Checking For An Intermittent DTC

3. (K141) O2 1/2 SIGNAL CIRCUIT SHORTED TO VOLTAGE

Turn the ignition off.
Disconnect the Oxygen Sensor 1/2 harness connector.
Turn the ignition on.
Measure the voltage on the (K141) O2 1/2 Signal circuit in the Oxygen Sensor 1/2 harness connector.

NOTE: Measure the voltage in reference to ground, not the (K904) O2 1/2 Return circuit.

Is the voltage above 5.2 volts?

Yes

- Repair the (K141) O2 1/2 Signal circuit for a short to voltage.
- Perform the PCM Verification Test Ver. 1Powertrain Verification Test.

No

- Go to 4

4. (K904) O2 1/2 RETURN CIRCUIT SHORTED TO VOLTAGE

Turn the ignition off.
Disconnect the Powertrain Control Module (PCM) harness connector.
Turn the ignition on.
Measure the voltage on the (K904) O2 1/2 Return circuit in the Oxygen Sensor 1/2 harness connector.
Is there any voltage present?

Yes

- Repair the (K904) O2 1/2 Return circuit for a short to voltage.
- Perform the PCM Verification Test Ver. 1Powertrain Verification Test.

No

- Go to 5

5. (K141) O2 1/2 SIGNAL CIRCUIT SHORTED TO GROUND

Turn the ignition off.
Measure the resistance between ground and the (K141) O2 1/2 Signal circuit in the Oxygen Sensor 1/2 harness connector.
Is the resistance below 100 ohms?

Yes

- Repair the (K141) O2 1/2 Signal circuit for a short to ground.
- Perform the PCM Verification Test Ver. 1Powertrain Verification Test.

No

- Go to 6

6. (K904) O2 1/2 RETURN CIRCUIT SHORTED TO GROUND

Measure the resistance between ground and the (K904) O2 1/2 Return circuit in the Oxygen Sensor 1/2 harness connector.
Is the resistance below 100 ohms?

Yes

- Repair the (K904) O2 1/2 Return circuit for a short to ground.
- Perform the PCM Verification Test Ver. 1Powertrain Verification Test.

No

- Go to 7

7. (K141) O2 1/2 SIGNAL CIRCUIT OPEN OR HIGH RESISTANCE

NOTE: When checking circuits at the Powertrain Control Module (PCM), be careful not to damage or distort the connector terminals. Improper measurement technique could result in poor pin to terminal contact.

Measure the resistance of the (K904) O2 1/2 Return circuit between the Oxygen Sensor 1/2 harness connector to the Powertrain Control Module (PCM) harness connector.
Is the resistance below 5.0 ohms?

Yes

- Go to 9

No

- Repair the (K904) O2 1/2 Return circuit for an open circuit or high resistance.
- Perform the PCM Verification Test Ver. 1Powertrain Verification Test.

9. OXYGEN SENSOR 1/2
NOTE: Prior to replacing the O2 sensor, verify that the correct part number is being used in order to prevent improper O2 heater control.

Using the wiring diagram/schematic as a guide, inspect the wiring and connectors between the Oxygen Sensor 1/2 and the Powertrain Control Module (PCM).
Look for any chafed, pierced, pinched, or partially broken wires.
Look for broken, bent, pushed out or corroded terminals.
Search for any Technical Service Bulletins that may apply.
Were any problems found?

Yes

- Repair as necessary.
- Perform the PCM Verification Test Ver. 1Powertrain Verification Test.

No

- Replace the Oxygen Sensor 1/2.
- Perform the PCM Verification Test Ver. 1Powertrain Verification Test.

10. EXHAUST LEAK
Repair the exhaust leak(s) as necessary.
Start the engine and allow it to reach operating temperature.
Test drive the vehicle for at least 5 minutes.
During the test drive, accelerate from 64 kph (40 mph) to 80 kph (50 mph), then release the accelerator pedal for at least 3 seconds. Repeat this procedure a minimum of 10 times.
Stop the vehicle and turn the ignition off for 5 seconds.
Test drive the vehicle again for at least 5 minutes.
During the test drive, accelerate from 64 kph (40 mph) to 80 kph (50 mph), then release the accelerator pedal for at least 3 seconds. Repeat this procedure a minimum of 10 times.
Stop the vehicle.
With the scan tool, select View DTCs.
Does this DTC reset as a pending or stored DTC?

Yes

- Retest. Go to 1

No

- Test Complete.
- Perform the PCM Verification Test Ver. 1Powertrain Verification Test.