P0156
DTC P0156 HO2S CIRCUIT (BANK 2/SENSOR 2)
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 circuit voltage is higher than 4.5 V after 5 V is applied to the HO2S output line via a resistor, the PCM judged as a open circuit and DTC is set.
Schematic Diagram:
MONITOR SCANTOOL DATA
1. Warm up the engine to normal operating temperature.
2. Connect Scantool then, Ignition "ON" & Engine "ON"
3. Monitor the "HO2S VOLTAGE(B2S2)" parameter on scantool.
Specification : Appox. 0.6 - 0.7 Volts
4. Is the HO2S VOLT.(B2/S2) parameter displayed 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 "W/Harness Inspection" procedure.
TERMINAL&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. Check for open in harness
1. Ignition "OFF"
2. Disconnect HO2 sensor connector and PCM connector.
3. Measure resistance between terminal 1 of HO2 sensor harness connector and terminal 3/C44-3 of PCM harness connector.
Specification : Approx.below 1 Ohm
4. Is the measured resistance within specifications?
YES: Go to " Ground Circuit Inspection " procedure.
NO:
- Check open in harness between HO2S harness connector and PCM connector.
- Repair or replace as necessary and then, go to " Verification of Vehicle Repair" procedure.
GROUND CIRCUIT INSPECTION
1. Check for open in harness
1. Ignition "OFF"
2. Disconnect HO2 sensor.
3. Measure resistance between terminal 2 of HO2 sensor harness connector and chassis ground.
Specification : Approx. below 1 Ohm
4. Is the measured resistance within specifications?
YES: Go to " Component Inspection " procedure.
NO:
- Check open in harness between HO2S connector and PCM connector.
- Repair or replace as necessary and then, go to " Verification of Vehicle Repair" 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 HO2 sensor signal connector.
5. Does the HO2 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 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.