P0139
DTC P0139 HO2S CIRCUIT SLOW RESPONSE (BANK 1 / SENSOR 2)Component Location:
GENERAL DESCRIPTION
HO2S (B1/S2) is in the back of Catalytic Converter to check the proper operation of catalyst. As Exhaust gas already passed through catalyst, oxygen density in it is within specific range. If the oxygen density changes in accordance with HO2S (B1/S1), it means the poor performance of catalytic converter.
DTC DESCRIPTION
Checking the Maximum time allowed between the front sensor response and the rear sensor response under detecting condition, if the difference time is higher than 25 sec., PCM determines a fault and sets DTC P0139. MIL (Malfunction Indication Lamp) turns on when the malfunction lasts till consecutive 2 driving cycle.
DTC Detecting Condition:
SPECIFICATION:
Air/fuel mixture Voltage
Rich 0.75 - 1 V
Lean 0 - 0.12 V
Schematic Diagram:
SIGNAL WAVEFORM AND DATA
Signal Waveform And Data:
The amplitude of the signal output of the rear HO2S is small compared to the front HO2S because the rear HO2S detects emission gas purified by the catalytic converter. This is the normal signal waveform of the rear HO2S at idle.
MONITOR SCANTOOL DATA
1. Connect Scantool then Engine "ON"
2. Warm up the engine to normal operating temperature.
3. Monitor the signal waveform of HO2S (B1S2) with scantool
Specification : 0.1 - 0.9 V
4. Is the shift time from signal waveform within specifications?
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 "Terminal and Connector Inspection" procedure.
TERMINAL AND CONNECTOR INSPECTION
1. Many malfunctions In the electrical system are caused by poor harness and terminals. Faults can also be caused by interference from other electrical systems, and mechanical or chemical damage.
2. Thoroughly check connectors for looseness, poor connection, bending, corrosion, contamination, deterioration, or damage.
3. Has a problem been found?
YES - Repair as necessary and go to "Verification of Vehicle Repair" procedure.
NO - Go to "Signal Circuit Inspection" procedure.
COMPONENT INSPECTION
1. Visual Inspection of HO2S
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 (B1/S2) O.K?
YES - 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.
NOTE: There is a memory reset function on scantool that can erase optional parts automatically detected and memorized by PCM.
NO - Substitute with a known - good HO2S (B1 S2) and check for proper operation. If the problem is corrected, replace HO2S (B1 S2) 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 test 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.