P0038
3MZ-FE ENGINE CONTROL SYSTEM: SFI SYSTEM: P0037: Oxygen Sensor Heater Control Circuit Low (Bank 1 Sensor 2)
DTC P0037 - Oxygen Sensor Heater Control Circuit Low (Bank 1 Sensor 2)
DTC P0038 - Oxygen Sensor Heater Control Circuit High (Bank 1 Sensor 2)
DTC P0057 - Oxygen Sensor Heater Control Circuit Low (Bank 2 Sensor 2)
DTC P0058 - Oxygen Sensor Heater Control Circuit High (Bank 2 Sensor 2)
DTC P0141 - Oxygen Sensor Heater Circuit Malfunction (Bank 1 Sensor 2)
DTC P0161 - Oxygen Sensor Heater Circuit Malfunction (Bank 2 Sensor 2)
DESCRIPTION
The heated oxygen sensor (HO2S) is used to monitor oxygen in the exhaust gas. For optimum catalyst operation, the air fuel mixture (air-fuel ratio) must be maintained near the ideal "stoichiometric" ratio. The HO2S output voltage changes suddenly in the vicinity of the stoichiometric ratio. The ECM (Included in HV control ECU) adjusts the fuel injection time so that the air-fuel ratio is nearly stoichiometric.
The HO2S generates a voltage between 0.1 and 0.9 V in response to oxygen in the exhaust gas. If the oxygen in the exhaust gas increases, the air-fuel ratio becomes "Lean". The ECM interprets Lean when the HO2S voltage is below 0.45 V. If the oxygen in the exhaust gas decreases, the air-fuel ratio becomes "Rich". The ECM interprets Rich when the HO2S voltage is above 0.45 V.
HINT:
- Sensor 2 refers to the sensor mounted behind the Three-Way Catalytic Converter (TWC) and located far from the engine assembly.
- When any of these DTCs are set, the ECM (Included in HV control ECU) 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 off.
- The HO2 sensor heater circuit uses a relay on the B+ side of the circuit.
HINT:
- Bank 1 refers to the bank that includes cylinder No. 1.
- Bank 2 refers to the bank that does not include cylinder No. 1.
- Sensor 1 refers to the sensor closest to the engine assembly.
- Sensor 2 refers to the sensor farthest away from the engine assembly.
MONITOR DESCRIPTION
The sensing position 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 concentrations 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 (Included in HV control ECU) supplements the heat from the exhaust with heat from a heating element inside the sensor.
Heated oxygen sensor heater range check (P0037 and P0038):
The ECM (Included in HV control ECU) monitors the current applied to the O2 sensor heater to check the heater for malfunctions. If the current is below the threshold value, the ECM determines that there is an open circuit in the heater. If the current is above the threshold value, the ECM determines that there is a short circuit in the heater.
The ECM constantly monitors the current applied to the heater. If the ECM (Included in HV control ECU) detects an open or short circuit, the ECM turns the MIL on and sets a DTC.
If a malfunction is detected, the ECM cuts off the current applied to the heater.
Example:
The ECM sets DTC P0038 when the current in the HO2 sensor heater is more than 2 A. Conversely, when the heater current is less than 0.3 A, DTC P0037 is set.
Heated oxygen sensor heater performance (P0141):
After the accumulated heater ON time exceeds 100 seconds, the ECM (Included in HV control ECU) 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 HO2 sensor heater and sets DTC P0141.
MONITOR STRATEGY
TYPICAL ENABLING CONDITIONS
All:
P0037 and P0057:
P0038 and P0058 Case 1:
P0038 and P0058 Case 2:
P0141 and P0161:
TYPICAL MALFUNCTION THRESHOLDS
P0037 and P0057:
P0038 and P0058 Case 1:
P0038 and P0058 Case 2:
P0141 and P0161:
COMPONENT OPERATING RANGE
MONITOR RESULT
- Refer to Checking Monitor Status Mode 6 Data.
The test value and test limit information are described as shown in the following table. Check the monitor result and test values after performing the monitor drive pattern Monitors, Trips, Drive Cycles and Readiness Codes.
- MID (Monitor Identification Date) is assigned to each emission-related component.
- TID (Test Identification Date) is assigned to each emission-related component.
- Scaling is used to calculate the test value indicated on generic OBD II scan tools.
Heated oxygen sensor heater:
WIRING DIAGRAM
INSPECTION PROCEDURE
HINT:
- 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 Techstream. The ECM (Included in HV control ECU) records vehicle and driving condition information as freeze frame data the moment a DTC is stored. 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
1. INSPECT HEATED OXYGEN SENSOR (HEATER RESISTANCE)
(a) Disconnect the H20 or H11 heated oxygen (HO2) sensor connectors.
(b) Measure the resistance between the terminals of the HO2 sensor connector.
Standard resistance (Bank 1 sensor 2):
Standard resistance (Bank 2 sensor 2):
(c) Reconnect the HO2 sensor connector.
NG -- REPLACE HEATED OXYGEN SENSOR
OK -- Continue to next step.
2. INSPECT IGCT RELAY
(a) Remove the IGCT relay from the engine room R/B.
(b) Inspect the IGCT relay.
Standard resistance:
(c) Reinstall the IGCT relay.
NG -- REPLACE IGCT RELAY
OK -- Continue to next step.
3. INSPECT HV CONTROL ECU (HT1B OR HT2B VOLTAGE)
(a) Turn the ignition switch to the ON position.
(b) Measure the voltage between the terminals of the H29, H31 and H33 HV control ECU connectors.
Standard voltage:
HINT:
- The HT1B means the heated oxygen sensor bank 1 sensor 2.
- The HT2B means the heated oxygen sensor bank 2 sensor 2.
OK -- REPLACE HV CONTROL ECU
NG -- Continue to next step.
4. CHECK HARNESS AND CONNECTOR (HEATED OXYGEN SENSOR - IGCT NO. 4 FUSE)
(a) Check the IGCT No. 4 fuse.
(1) Remove the IGCT No. 4 fuse.
(2) Measure the resistance IGCT No. 4 fuse.
Standard resistance:
Below 1 Ohms
(3) Reinstall the IGCT No. 4 fuse.
(b) Check the harness and connector between the HO2 sensor and IGCT No. 4 fuse.
(1) Disconnect the H11 or H20 HO2 sensor connector.
(2) Remove the IGCT No. 4 fuse from the R/B No. 3.
(3) Measure the resistance according to the value(s) in the table below.
Standard resistance:
Standard resistance:
(4) Reconnect the HO2 sensor connector.
(5) Reinstall the IGCT No. 4 fuse.
NG -- REPAIR OR REPLACE HARNESS OR CONNECTOR
OK -- Continue to next step.
5. CHECK HARNESS AND CONNECTOR (HEATED OXYGEN SENSOR - HV CONTROL ECU)
(a) Check the harness and connector between the HV control ECU and HO2 sensor.
(1) Disconnect the H20 or H11 HO2 sensor connector.
(2) Remove the H29 and H33 HV control ECU connectors.
(3) Measure the resistance according to the value(s) in the table below.
Standard resistance:
(4) Reconnect the HO2 sensor connector.
(5) Reconnect the HV control ECU connector.
NG -- REPAIR OR REPLACE HARNESS OR CONNECTOR
OK -- CHECK FOR INTERMITTENT PROBLEMS