P0157
DTC P0157 HO2S CIRCUIT LOW VOLTAGE (BANK 2 / SENSOR 2)Component Location:
GENERAL DESCRIPTION
HO2S(B2/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(B2/S2), it means the poor performance of catalytic converter.
DTC DESCRIPTION
Checking output signals from HO2S every 15 sec. under detecting condition, if an output signal is below 0.05 V for more than 12.5 sec., PCM sets P0157. MIL(Malfunction Indication Lamp) turns on when the malfunction lasts till consecutive 2 driving cycle.
DTC Detecting Condition:
Specification:
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. IG "OFF" & connect Scantool.
2. ENG "ON" and warm -up the engine to normal operating temperature.
3. Monitor "HO2S(B2/S2)" item on the service data.
4. Is the service data displayed correctly?
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, ending, 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.
SIGNAL CIRCUIT INSPECTION
1. IG "OFF" and disconnect HO2S(B2/S2)
2. IG "ON"
3. Measure voltage between terminal 3 of HO2S(B2/S2) harness connector and chassis ground.
Specification :
Approx.3.5 V - when pumping current is ON
Approx.0.45 V - when pumping current is OFF
4. Is the measured voltage within specification?
YES: Go to "Component Inspection" procedure.
NO: Repair short to ground in harness, and go to "Verification of Vehicle Repair" 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(B2/S2) normal?
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.
NO: Substitute with a known - good HO2S(B2/S2) and check for proper operation. If the problem is corrected, replace HO2S(B2/S2) 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. Before or after testing PCM on the vehicle, use this function to reuse the PCM on the others
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 trouble shooting procedure.
NO: System is performing to specification at this time.