SFI SYSTEM (w/ Secondary Air Injection System), Diagnostic DTC:P0037, P0038, P0141
| DTC Code | DTC Name |
|---|---|
| P0037 | Oxygen Sensor Heater Control Circuit Low (Bank 1 Sensor 2) |
| P0038 | Oxygen Sensor Heater Control Circuit High (Bank 1 Sensor 2) |
| P0141 | Oxygen Sensor Heater Circuit Malfunction (Bank 1 Sensor 2) |
DESCRIPTION
Tech Tips
Sensor 2 refers to the sensor mounted behind the Three-Way Catalytic Converter (TWC) and located far from the engine assembly.
Refer to DTC P0136 Click here.
Tech Tips
-
When either of these DTCs are set, the ECM enters fail-safe mode. The ECM turns off the Heated Oxygen (HO2) sensor heater in fail-safe mode. Fail-safe mode continues until the ignition switch is turned to off.
-
The ECM provides a pulse width modulated control circuit to adjust the current through the heater. The HO2 sensor heater circuit uses a relay on the +B side of the circuit.
| DTC No. | DTC Detection Conditions | Trouble Areas |
|---|---|---|
| P0037 | Heated Oxygen (HO2) sensor heater current less than 0.3 A (1 trip detection logic) |
|
| P0038 | Heated Oxygen (HO2) sensor heater current more than 2 A (1 trip detection logic) |
|
| P0141 | Cumulative heater resistance correction value exceeds threshold (2 trip detection logic) |
|
MONITOR DESCRIPTION
The sensing portion of the Heated Oxygen (HO2) sensor has a zirconia element which is used to detect the oxygen concentration in the exhaust gas. If the zirconia element is at the appropriate temperature, and the difference between the oxygen concentration surrounding the inside and outside surfaces of the sensor is large, the zirconia element generates voltage signals. In order to increase the oxygen concentration detecting capacity of the zirconia element, the ECM supplements the heat from the exhaust with heat from a heating element inside the sensor.
-
The ECM monitors the current applied to the heated oxygen sensor heater to check the heater for malfunctions. If the current is below the threshold value, the ECM will determine that there is an open circuit in the heater. If the current is above the threshold value, the ECM will determine that there is a short circuit in the heater.
-
Example:
-
The ECM stores DTC P0038 when the current in the heated oxygen sensor heater is more than 2 A. Conversely, when the heater current is less than 0.3 A, DTC P0037 is stored.
Heated Oxygen Sensor Heater Range Check (P0037 and P0038):
-
After the accumulated heater ON time exceeds 100 seconds, the ECM calculates the heater resistance using the battery voltage and the current applied to the heater.
If the resistance is above the threshold value, the ECM determines that there is a malfunction in the heated oxygen sensor heater and stores DTC P0141.
Heated oxygen sensor heater performance (P0141):
WIRING DIAGRAM
Refer to DTC P0136 Click here.
INSPECTION PROCEDURE
Tech Tips
-
If other DTCs relating to different systems that have terminal E2 as the ground terminal are output simultaneously, terminal E2 may have an open circuit.
-
Read freeze frame data using the intelligent tester. Freeze frame data records the engine condition when malfunctions are detected. When troubleshooting, freeze frame data can help determine if the vehicle was moving or stationary, if the engine was warmed up or not, if the air fuel ratio was lean or rich, and other data from the time the malfunction occurred.
PROCEDURE
-
INSPECT HEATED OXYGEN SENSOR (HEATER RESISTANCE)
-
Inspect the Heated Oxygen (HO2) sensor Click here.
NG 
REPLACE HEATED OXYGEN SENSOR
OK 
-
-
INSPECT INTEGRATION RELAY
-
Inspect the integration relay (MAIN relay) Click here.
NG
REPLACE INTEGRATION RELAY
OK
-
-
REPLACE ECM
-
Text in Illustration *a Component with wire harness connected
(ECM)
Turn the ignition switch to ON.
-
Measure the voltage according to the value(s) in the table below.
Voltage Tester Connections Switch Condition Specified Conditions D1-2 (HT1B) - D3-4 (E03) Ignition switch ON 11 to 14 V
NG 
CHECK HARNESS AND CONNECTOR (HO2 SENSOR - ECM, HO2 SENSOR - INTEGRETION RELAY) Click here
OK 
REPLACE ECM
-
-
CHECK HARNESS AND CONNECTOR (HO2 SENSOR - ECM, HO2 SENSOR - INTEGRETION RELAY)
-
Check the harness and connectors between the ECM and HO2 sensor.
-
Disconnect the HO2 sensor connector.
-
Disconnect the ECM connector.
-
Measure the resistance according to the value(s) in the table below.
Resistance (Check for open) Tester Connections Condition Specified Conditions D35-1 (HT1B) - D1-2 (HT1B) Always Below 1 Ω Resistance (Check for short) Tester Connections Condition Specified Conditions D35-1 (HT1B) or D1-2 (HT1B) - Body ground Always 10 kΩ or higher -
Reconnect the HO2 sensor connector.
-
Reconnect the ECM connector.
-
-
Check the harness and connector between the HO2 sensor and Integration relay (MAIN relay).
-
Disconnect the HO2 sensor connector.
-
Remove the integration relay from the engine room R/B No.1.
-
Measure the resistance according to the value(s) in the table below.
Resistance (Check for open) Tester Connections Condition Specified Conditions D35-2 (+B) - 1J-4 Always Below 1 Ω Resistance (Check for short) Tester Connections Condition Specified conditions D35-2 (+B) or 1J-4 - Body ground Always 10 kΩ or higher -
Reconnect the HO2 sensor connector.
-
Reinstall the integration relay (MAIN relay).
-
NG
REPAIR OR REPLACE HARNESS OR CONNECTOR
OK
REPLACE ECM
-