P0139
DTC P0139 HO2S CIRCUIT SLOW RESPONSE (BANK 1/ SENSOR 2)Component Location:
COMPONENT LOCATION
GENERAL DESCRIPTION
The rear heated oxygen sensor is mounted on the rear side of the Catalytic Converter (warm-up catalytic converter) or in the rear exhaust pipe, which detects the catalyst efficiency. The rear heated oxygen sensor (HO2S) produces a voltage between 0 V and 1 V. This rear heated oxygen sensor is used to estimate the oxygen storage capability. If a catalyst has good conversion properties, the oxygen fluctuations are smoothed by the oxygen storage capacity of the catalyst. If the conversion provided by the catalyst is low due to aging, poisoning or misfiring, then the oxygen fluctuations are similar to signals from the front oxygen sensor.
DTC DESCRIPTION
If the rear HO2S signal's response time from rich to lean is longer than 1 second while engine is in fuel cut-off and Engine coolant temperature is over 82 °C (179.6 °F),the PCM determines that a fault exists and a DTC is stored.
DTC Detecting Condition:
Schematic Diagram:
Signal Waveform & Data:
MONITOR SCANTOOL DATA
1. Warm up the engine to normal operating temperature.
2. Connect Scantool then, Ignition "ON" & Engine "ON"
DTC Detecting Condition:
3. Monitor the response time is within the specification as below.
Specification: Approx. Within 1 sec.
4. Is the shift time from signal waveform within specification?
YES: Fault is intermittent caused by poor contact in the sensor's and/or PCM's connector or was repaired and PCM memory was not cleared. Thoroughly check connectors for looseness, poor connection, bending, corrosion, contamination, deterioration, or damage. Repair or replace as necessary and go to "Verification of Vehicle Repair" procedure.
NO: Go to "Component Inspection" procedure.
COMPONENT INSPECTION
1. Visual Inspection of HO2S
1. Visually/physically inspect following items:
- Inspect the rear HO2S for Contaminated, deteriorated or aged Rear HO2S.
- If contamination is evident on the HO2S, replace contaminated sensor.
2. Is the HO2S visually / physically O.K.?
YES: Go to "Check PCM" as below.
NO:
- Substitute with a known - good HO2S and check for proper operation.
- If the problem is corrected, replace HO2S and go to "Verification of Vehicle Repair" procedure.
2. Check PCM
1. Ignition "OFF" & Engine "OFF"
2. Connect Scantool and Ignition "ON"
3. Select simulation function on scantool.
4. Simulate voltage at terminal 1 of HO(2) sensor signal connector.
5. Does the HO(2) sensor signal value changes according to simulation voltage?
YES: Fault is intermittent caused by poor contact in the sensor's and/or PCM's connector. Thoroughly check connectors for looseness, poor connection, bending, corrosion, contamination, deterioration, or damage. Repair or replace as necessary and go to "Verification of Vehicle Repair" procedure.
NO: Substitute with a known - good PCM and check for proper operation.
If the problem is corrected, replace PCM and go to "Verification of Vehicle Repair" procedure.
VERIFICATION OF VEHICLE REPAIR
After a repair, it is essential to verify that the fault has been corrected.
1. Monitor and record the Freeze Frame Data for the Diagnostic Trouble Code(DTC) which has been diagnosed.
2. Using a Scantool, Clear the DTCs.
3. Operate the vehicle within conditions noted in the freeze frame data or enable conditions.
4. Monitor that all readiness tests have been verified as "Complete".
5. Are any DTCs present?
YES: Go to the applicable troubleshooting procedure.
NO: System is performing to specification at this time.