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)
CAUTION / NOTICE / HINT
HINT: Sensor 2 refers to the sensor mounted behind the Three-Way Catalytic Converter (TWC) and located furthest from the engine assembly.
DESCRIPTION
Sensor 2 refers to the sensor mounted behind the Three-Way Catalytic Converter (TWC) and located far from the engine assembly.
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 adjusts the fuel injection time so that the air-fuel ratio is nearly stoichiometirc.
The HO2S generates a voltage between 0.1 and 0.9 volts 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 volts. 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 volts.
HINT:
- When any 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 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 furthest 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 supplements the heat from the exhaust with heat from a heating element inside the sensor.
Heated oxygen sensor heater range check (P0037,P0038, P0057 and P0058):
- The ECM 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 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 sets DTC P0038 or P0058 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 or P0057 is set.
Heated oxygen sensor heater performance (P0141 and P0161):
- 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 will determine that there is a malfunction in the HO2S heater and set DTC P0141 and P0161.
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:
P0141 and P0161 (Heater performance monitor check):
COMPONENT OPERATING RANGE
MONITOR RESULT
Refer to CHECKING MONITOR STATUS (Mode 6 Data).
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 records vehicle and driving condition information as freeze frame data the moment a DTC is stored. When troubleshooting, freeze frame data can be helpful in determining whether the vehicle was running or stopped, whether the engine was warmed up or not, whether the air-fuel ratio was lean or rich, as well as other data recorded at the time of a malfunction.
PROCEDURE
1. INSPECT HEATED OXYGEN SENSOR (HEATER RESISTANCE)
(a) Disconnect the heated oxygen sensor connector (Bank 1 Sensor 2) or heated oxygen sensor connector (Bank 2 Sensor 2).
(b) Measure the resistance between the terminals of the HO2 sensor connector.
Standard resistance:
Bank 1
Bank 2
(c) Reconnect the HO2 sensor connector.
NG -- REPLACE HEATED OXYGEN SENSOR
OK -- Continue to next step.
2. INSPECT EFI RELAY
(a) Remove the EFI relay from the engine room J/B.
(b) Measure the EFI relay resistance.
Standard resistance:
(c) Reinstall the EFI relay.
NG -- REPLACE EFI MAIN RELAY
OK -- Continue to next step.
3. INSPECT ECM (HT1B OR HT2B VOLTAGE)
(a) Turn the ignition switch to the ON position.
(b) Measure the voltage between the terminals of the ECM 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 ECM
NG -- Continue to next step.
4. CHECK HARNESS AND CONNECTOR (HEATED OXYGEN SENSOR - ECM, HEATED OXYGEN SENSOR - EFI RELAY)
(a) Check the harness and the connector between the ECM and the HO2 sensor.
(1) Disconnect the heated oxygen sensor connector (Bank 1 Sensor 2) or heated oxygen sensor connector (Bank 2 Sensor 2).
(2) Disconnect the ECM connector.
(3) Measure the resistance.
Standard resistance:
Check for open
Standard resistance:
Check for short
(b) Check the harness and the connectors between the heated oxygen sensor and EFI relay.
(1) Remove the EFI relay from the engine room J/B.
(2) Measure the resistance between the terminals.
Standard resistance:
Check for open
Standard resistance:
Check for short
(c) Reconnect the HO2 sensor connector.
(d) Reconnect the ECM connector.
(e) Reinstall the EFI relay.
NG -- REPAIR OR REPLACE HARNESS OR CONNECTOR
OK -- REPLACE ECM