P0139

P0139-O2 SENSOR 1/2 SLOW RESPONSE





For a complete wiring diagram Consult Diagrams/Electrical.

- When Monitored:
Vehicle is started and driven between 20 and 55 MPH with the Throttle open for a minimum of 120 seconds. Coolant greater than 70°C (158°F). Catalytic Converter Temp greater than 600°C (1112°F) and EVAP Purge is active.

- Set Condition:
The oxygen sensor signal voltage switches less than 16 times from lean to rich within 20 seconds during monitoring. 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.

Diagnostic Test

1. ACTIVE DTC

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

Ignition on, engine not running.

NOTE: After the repairs have been made, verify proper O2 Sensor operation. If all the O2 Sensor voltage readings have not returned to normal, follow the diagnostic procedure for the remaining O2 Sensors.

With a scan tool, read DTCs.
Is the DTC active at this time?

Yes

- Go To 2

No

- Refer to the INTERMITTENT CONDITION Diagnostic Procedure.Intermittent Condition
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test

2. CHECKING THE EXHAUST SYSTEM FOR LEAKS
Perform the diagnostic procedure for *CHECKING THE EXHAUST SYSTEM FOR LEAKS.
Were any problems found?

Yes

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

No

- Go to 3

3. (K141) O2 1/2 SIGNAL CIRCUIT




Turn the ignition off
Disconnect the 1/2 O2 Sensor harness connector.
Ignition on, engine not running.
Measure the voltage on the (K141) O2 1/2 Signal circuit in the O2 Sensor harness connector.
Is the voltage between 4.5 and 5.0 volts?

Yes

- Go To 4

No

- Check the (K141) O2 1/2 Signal circuit for a short to ground, open, or short to voltage. If OK, replace and program the Powertrain Control Module.
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test

4. (K902) O2 DOWNSTREAM RETURN CIRCUIT




Measure the voltage on the (K902) O2 Downstream Return circuit in the 1/2 O2 Sensor harness connector.
Is the voltage at 2.5 volts?

Yes

- Go To 5

No

- Check the (K902) O2 Downstream Return circuit for a short to ground, open, or short to voltage. If OK, replace and program the Powertrain Control Module.
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test

5. O2 SENSOR
If there are no possible causes remaining, view repair.

Repair

- Replace the O2 Sensor
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test