P0140
P0140-O2 SENSOR 1/2 NO ACTIVITY DETECTED
For a complete wiring diagram, refer to the Wiring Information.
Theory of Operation
The Downstream O2 Sensor is located in the exhaust path behind the Catalytic Converter, is monitored for proper response to assure optimum Catalytic Converter efficiency. The Downstream O2 Sensor response monitor is intended to diagnose a Downstream O2 Sensor that is not moving or stuck in a voltage window and to insure accurate information for catalyst monitor diagnosis.
- When Monitored:
With the engine running, vehicle speed between 32 and 88 kph (20 and 55 mph), throttle open for a minimum of 120 seconds, ECT greater than 70°C (158°F), Catalytic Converter Temperature greater than 600°C (1112°F) and EVAP Purge active.
- Set Condition:
The Powertrain Control Module (PCM) detects that the Oxygen Sensor 1/2 signal switches from lean to rich less than 16 times 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. PCM Pre-Diagnostic Troubleshooting Procedure.
Diagnostic Test
1. ACTIVE DTC
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.
NOTE: Check for contaminants that may have damaged the O2 Sensor: contaminated fuel, unapproved silicone, oil and coolant.
1. Start the engine.
2. Allow the engine to reach normal operating temperature.
3. With the scan tool, select View DTCs.
NOTE: It may be necessary to drive the vehicle to meet the conditions to set this DTC, try to repeat the conditions in which the fault originally set by reviewing the Freeze Frame data.
Is the DTC Active or Pending at this time?
Yes
- Go To 2
No
- Perform the INTERMITTENT CONDITION diagnostic procedure. PCM Intermittent Condition Test.
2. CHECKING THE EXHAUST SYSTEM FOR LEAKS
1. Perform the CHECKING THE EXHAUST SYSTEM FOR LEAKS test procedure. Checking The Exhaust System For Leaks.
Were any exhaust leaks found?
Yes
- Perform the appropriate repairs.
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test.
No
- Go To 3
3. CHECK THE (K141) O2 SENSOR 1/2 1/2 SIGNAL CIRCUIT
1. Turn the ignition off
2. Disconnect the O2 Sensor 1/2 harness connector.
3. Ignition on, engine not running.
4. Measure the voltage on the (K141) O2 Sensor 1/2 Signal circuit in the O2 Sensor 1/2 harness connector.
Is the voltage between 4.1 and 5.0 volts?
Yes
- Go To 4
No
- Check the (K141) O2 Sensor 1/2 Signal circuit for a short to ground, open or short to voltage. If OK, replace and program the PCM. Powertrain Control Module - Removal.
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test.
4. CHECK THE (K904) O2 SENSOR 1/2 RETURN CIRCUIT
1. Measure the voltage on the (K904) O2 Sensor 1/2 Return circuit in the O2 Sensor 1/2 harness connector.
Is the voltage at 2.5 volts?
Yes
- Go To 5
No
- Check the (K904) O2 Sensor 1/2 Return circuit for a short to ground, open or short to voltage. If OK, replace and program the PCM. Powertrain Control Module - Removal.
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test.
5. OXYGEN SENSOR
NOTE: Check for signs of contaminants that may have damaged the O2 Sensor 1/2, such as contaminated fuel, unapproved silicone, oil and coolant.
1. Using the wiring diagram/schematic as a guide, inspect the wiring and connectors between the O2 Sensor 1/2 and the Powertrain Control Module (PCM).
2. Look for any chafed, pierced, pinched or partially broken wires.
3. Look for broken, bent, pushed out or corroded terminals.
4. Perform any Technical Service Bulletins that may apply.
Were any problems found?
Yes
- Repair as necessary.
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test.
No
- Replace the Oxygen Sensor 1/2. Oxygen Sensor - Removal.
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test.