4.
Read "DTC Status" parameter.
The normal operating temperature of the HO2S(Heated Oxygen Sensor) ranges 350 to 850℃(662 to 1562℉). The HO2S heater greatly decreases the amount of time required for fuel control to become active. The ECM provides a pulse width modulated control circuit to adjust current through the heater. When the HO2S is cold, the value of the resistance is low and the current in the circuit is high. On the contrary, the temperature in the resistor of the sensor rises, the current drops gradually.
ECM sets DTC P0038 if the ECM detects that the rear HO2S heater control line is open or short to battery line.
Item | Detecting Condition | Possible Cause |
DTC Strategy | ● Check open or short circuit to battery line on front HO2S heater line | ● Open or short to battery in control harness ● Contact resistance in connectors ● Faulty HO2S |
Enable Conditions | ● Battery voltage〉10V ● 1%〈Heater power〈99% | |
Threshold Value | ● Open or short to Battery | |
Diagnostic Time | ● 20 sec. | |
Fail Safe | ● Heater open loop control |
HO2S Heater | Normal Parameter |
20℃ (68℉) | |
Heater Resistance | Approx. 3~4Ω |
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 connections, 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 "Control Circuit Inspection" procedure.
Check for open in control harness
Ignition "OFF".
Disconnect HO2S and ECM connectors.
Measure resistance between terminals 4 of the HO2S heater harness connector and 7 of the ECM harness connector.
Specification : Approx. 0Ω
Is resistance within the specification?
▶ Go to next step as below.
▶ Repair as necessary and go to "Verification of Vehicle Repair" procedure.
Check for short to power in control circuit.
Reconnect the ECM connector.
Ignition "ON" & Engine "OFF".
Measure voltage between terminal 4 of the HO2S heater harness connector and chassis ground.
Specification : Approx. 0V
Is voltage within the specification?
▶ Go to "Component Inspection" procedure.
▶ Repair as necessary and go to "Verification of Vehicle Repair" procedure.
Ignition "OFF".
Measure resistance between terminals 3 and 4 of the sensor connector (Component side).
Specification : 3~4Ω[at 20℃(68℉)]
Is resistance within the specification?
▶ 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.
