P0139

P0139-O2 SENSOR 1/2 SLOW RESPONSE






For a complete wiring diagram refer to: Electrical Diagrams

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.

Possible Causes
- EXHAUST LEAK
- (K141) O2 1/2 SIGNAL CIRCUIT
- (K904) O2 DOWNSTREAM RETURN CIRCUIT
- O2 SENSOR

Always perform the Pre-Diagnostic Troubleshooting procedure before proceeding.

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.
Perform POWERTRAIN VERIFICATION TEST. Powertrain Verification Test
2. EXHAUST LEAK
Start the engine.
Inspect the exhaust system for leaks between the engine and the O2 Sensors.

Are there any exhaust leaks?
Yes >> Repair or replace the leaking exhaust parts as necessary.
Perform POWERTRAIN 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 pro gram the Powertrain Control Module per Service Information.
Perform POWERTRAIN VERIFICATION TEST. Powertrain Verification Test
4. (K904) O2 DOWNSTREAM RETURN CIRCUIT





Measure the voltage on the (K904) 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 (K904) O2 Downstream Return circuit for a short to ground, open, or short to voltage. If OK, replace and program the Powertrain Control Module per Service Information.
Perform POWERTRAIN VERIFICATION TEST. Powertrain Verification Test
5. O2 SENSOR
If there are no possible causes remaining, view repair.

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