4.
Read "DTC Status" parameter.
The HO2S is used to supply the ECM with information regarding the composition of the air/fuel mixture. The HO2S is positioned in the exhaust pipe ahead of the TWC. To measure the oxygen content, the HO2S requires a supply of ambient air as a reference. Since this is supplied through the wiring, the lead must not be clamped or damaged in any other way. The HO2S produces a voltage that varies between 0.1V and 0.9V under normal operating conditions. The Engine Control Module (ECM) monitors this voltage and determines if the exhaust gas is lean or rich. If the voltage input at the ECM is under approx. 0.45V the exhaust is lean, and if the voltage input is over approx. 0.45V the exhaust is rich. The ECM constantly monitors the HO2S signal during closed loop operation and compensates for a rich or lean condition by decreasing or increasing injector pulse width as necessary.
The control unit of the linear oxygen sensor built inside the ECM monitors short circuit errors on all front Heated Oxygen Sensor (HO2S) control lines and the ECM sets P0131 with short circuit to ground.
ITEM | DETECING CONDITION | POSSIBLE CAUSE |
DTC Strategy | ●Sensor voltage low | ● Short to ground in signal harness ● Contact resistance in connectors ● Faulty Heated O2 Sensor.(HO2S) |
Enable Conditions | ●Sensor preheating and full heating phases finished ●Battery voltage ＞10V | |
Threshold Value | ●Sensor voltage ＜0.02V and element resistance ＜10Ω | |
Diagnostic Time | ●60 sec. |
Connect scan tool and select "Diagnostic Trouble Codes(DTCs)" mode.
Press F4(DTAL) to select DTC information from the DTCs menu.
Confirm that "DTC Readiness Flag" indicates "Complete". If not, drive the vehicle within conditions noted in the freeze frame data or enable conditions.
Read "DTC Status" parameter.
Is parameter displayed "History(Not Present) fault"?
History (Not Present) fault : DTC occurred but has been cleared.
Present fault : DTC is occurring at present time.
▶ 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.
▶ Go to next step as below.
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.
Thoroughly check connectors for looseness, poor connection, bending, corrosion, contamination, deterioration, or damage.
Has a problem been found?
▶ Repair as necessary and go to "Verification of Vehicle Repair" procedure.
▶ Go to "Signal Circuit Inspection" procedure.
Ignition "OFF"
Disconnect HO2S connector.
Measure resistance between terminal 1 of the HO2S harness connector and chassis ground.
Specification : Infinite
Is resistance within the specification?
▶ Go to "Component Inspection" procedure.
▶ Repair open in the signal circuit and go to "Verification of Vehicle Repair" procedure.
Visually/physically inspect following items:
Inspect the front HO2S for any silicon contamination. This contamination will be indicated by a white powdery coating and this will result in a but false voltage signal.
If contamination is evident on the HO2S, replace contaminated sensor and go to next step.
Warm up the engine to normal operating temperature and check that HO2S signal is active.
Connect Scantool and monitor the "FR OXYGEN SNSR-B1" parameter on the Scantool data list.
Specification : Verify signal is switching from rich(above 0.45V) to lean(below 0.45V) a minimum of 3 times in 10 seconds (voltage will vary between 0.1 and 0.9V).
Is sensor switching properly?
▶ 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.
▶ 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.
After a repair, it is essential to verify that the fault has been corrected.
Connect scan tool and select "Diagnostic Trouble Codes(DTCs)" mode.
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.
Read "DTC Status" parameter.
Is parameter displayed "History(Not Present) fault"?
▶ System performing to specification at this time. Clear the DTC.
▶ Go to the applicable troubleshooting procedure.
