P0038

P0038

Component Location:

General Description
The normal operating temperature of the HO2S (Heated Oxygen Sensor) ranges from 350 to 850 °C (662 to 1562 °F). The HO2S heater greatly decreases the amount of time required for fuel control to become active. The PCM 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, if the temperature in the resistor of the sensor rises, the current drops gradually.

DTC Description
If the PCM detects short to battery in heater under detecting conditions, PCM sets P0038. MIL (Malfunction Indication Lamp) turns on when the malfunction lasts till consecutive 2 driving cycle.

DTC Detecting Condition:

Specification:

Schematic Diagram:

Signal Waveform:

Monitor DTC Status
1. Check DTC Status
1. Connect scantool to Data Link Connector (DLC).
2. IG "ON".
3. Select "Diagnostic Trouble Codes ( DTCs)" mode, and then Press F5 ( INFO) to check DTC's information from the DTCs menu
4. Read "DTC Status" parameter.

5. Is parameter displayed "Present fault"?

YES - Go to "Terminal and Connector inspection" procedure.

NO - 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.

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 "Control Circuit Inspection " procedure.

Control Circuit Inspection
1. IG "OFF" & disconnect HO2S (B1/S2) connector.
2. IG "ON" & ENG "OFF".
3. Measure voltage between terminal 2 of HO2S (B1/S2) harness connector and chassis ground.

Specification : Approx. 0 V

4. Is the measured voltage within specification ?

YES - Go to HO2S (B1/S2) "Component Inspection" procedure.

NO - Repair short to battery in HO2S (B1/S2) heater control circuit and go to "Verification of Vehicle Repair" procedure.

Component Inspection
1. Check HO2S (B1/S2) Heater resistance
1. IG "OFF" and disconnect HO2S (B1/S2) connector
2. Measure resistance between terminal 1 and 2 of HO2S (B1/S2) (Component Side)

Specification :

3. Is the measured resistance within specification?

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.

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.

NO - Substitute with a known - good HO2S(B1/S2) and check for proper operation. If the problem is corrected, replace HO2S(B1/S2) 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. Connect scan tool and select "Diagnostic Trouble Codes (DTCs)" mode
2. Press F5 (INFO) 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.