P0156
DTC P0156 HO2S CIRCUIT (BANK 2 / SENSOR 2)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 0V and 1V. 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
ECM sets DTC P0136 if the ECM detects that the rear HO2S signal circuit is open.
DTC Detecting Condition:
Schematic Diagram:
Signal Waveform:
MONITOR DTC STATUS
1. Connect scan tool and select "Diagnostic Trouble Codes(DTCS)" mode.
2. Press F4(DTAL) to select DTC information from the DTCs menu.
3. Confirm that "DTC Readiness Flag" indicates "Complete". If not, drive the vehicle within conditions noted in the freeze frame data or enable conditions.
4. Read "DTC Status" parameter.
5. Is parameter displayed "History(Not Present) fault"?
NOTE:
- History (Not Present) fault: DTC occurred but has been cleared.
- Present fault: DTC is occurring at present time.
YES: Fault is intermittent caused by poor contact in the sensor's and/or ECM's connector or was repaired and ECM memory was not cleared. Thoroughly check connectors for loose or poor connection, bending, corrosion, contamination, deterioration, or damage. Repair or replace as necessary and go to "Verification of Vehicle Repair" procedure.
NO: Go to next step as below.
TERMINAL & CONNECTOR INSPECTION
1. Many malfunctions in the electrical system are caused by poor harness(es) 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 "Ground Circuit Inspection" procedure.
GROUND CIRCUIT INSPECTION
1. Ignition "OFF"
2. Disconnect HO2S and ECM connectors.
3. Measure resistance between terminal 2 of the sensor harness connector and 24 of the ECM harness connector.
Specification: Approx. 0 Ohm
4. Is resistance within the specification?
YES: Go to "Signal circuit inspection" procedure.
NO: Repair open in the signal circuit and go to "Verification of Vehicle Repair" procedure.
SIGNAL CIRCUIT INSPECTION
1. Measure resistance between terminals 1 of the HO2S harness connector and 18 of the ECM harness connector.
Specification: Approx. 0 Ohm
2. Is resistance within the specification?
YES: Go to "Component Inspection" procedure.
NO: Repair open in the ground circuit and go to "Verification of Vehicle Repair" procedure.
COMPONENT INSPECTION
1. Warm up the engine to normal operating temperature and check that HO2S signal is active.
2. Connect Scantool and monitor the "RR OXYGEN SNSR-B2" parameter on the Scantool data list.
Test Condition Engine "ON" & In Idle("Closed Loop")condition.
Specification: Above 0.6V.
3. Is sensor data within the specification?
YES: Check for poor connection between ECM and component: backed out terminal, improper mating, broken locks or poor terminal to wire connection. Repair as necessary and go to "Verification of Vehicle Repair" procedure.
NO: Check HO2S for contamination, deterioration, or damage. Substitute with a known-good HO2S and check for proper operation. If the problem is corrected, replace HO2S and then 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. Connect scan tool and select "Diagnostic Trouble Codes(DTCs)" mode.
2. Press F4(DTAL) and confirm that "DTC Readiness Flag" indicates "Complete". If not, drive the vehicle within conditions noted in the freeze frame data or enable conditions.
3. Read "DTC Status" parameter.
4. Is parameter displayed "History(Not Present) fault"?
YES: System performing to specification at this time. Clear the DTC.
NO: Go to the applicable troubleshooting procedure.