P0031
1GR-FE ENGINE CONTROL SYSTEM: SFI SYSTEM: P0031,P0032,P0051,P0052: Oxygen (A/F) Sensor Heater Control Circuit Low (Bank 1 Sensor 1)
CAUTION / NOTICE / HINT
HINT
* Although the DTC titles say the oxygen sensor, these DTCs relate to the Air-Fuel Ratio (A/F) sensor.
* Sensor 1 refers to the sensor mounted in front of the Three-Way Catalytic Converter (TWC) and located near the engine assembly.
DESCRIPTION
Refer to DTC P2195 P2195.
HINT
* When any of these DTCs are set, the ECM enters fail-safe mode. The ECM turns off the A/F sensor heater in fail-safe mode. Fail-safe mode continues until the ignition switch is turned off.
* The ECM provides a pulse width modulated control circuit to adjust the current through the heater. The A/F sensor heater circuit uses a relay on the +B side of the circuit.
MONITOR DESCRIPTION
The ECM uses information from the Air-Fuel Ratio (A/F) sensor to regulate the air-fuel ratio and keep it close to the stoichiometric level. This maximizes the ability of the Three-Way Catalytic Converter (TWC) to purify the exhaust gases.
The A/F sensor detects oxygen levels in the exhaust gas and transmits the information to the ECM. The inner surface of the sensor element is exposed to the outside air. The outer surface of the sensor element is exposed to the exhaust gas. The sensor element is made of platinum coated zirconia and includes an integrated heating element.
The zirconia element generates a small voltage when there is a large difference in the oxygen concentrations between the exhaust gas and outside air. The platinum coating amplifies this voltage generation.
The A/F sensor is more efficient when heated. When the exhaust gas temperature is low, the sensor cannot generate useful voltage signals without supplementary heating. The ECM regulates the supplementary heating using a duty-cycle approach to adjust the average current in the sensor heater element. If the heater current is outside the normal range, the signal transmitted by the A/F sensor becomes inaccurate, as a result, the ECM is unable to regulate air-fuel ratio properly.
When the current in the A/F sensor heater is outside the normal operating range, the ECM interprets this as a malfunction in the sensor heater and sets a DTC.
MONITOR STRATEGY
TYPICAL ENABLING CONDITIONS
All
P0031 and P0051
P0032 and P0052
TYPICAL MALFUNCTION THRESHOLDS
P0031 and P0051
P0032 and P0052
COMPONENT OPERATING RANGE
CONFIRMATION DRIVING PATTERN
1. Connect the Techstream to the DLC3.
2. Turn the ignition switch to ON and turn the Techstream on.
3. Clear the DTCs (even if no DTCs are stored, perform the clear DTC operation).
4. Turn the ignition switch off and wait for at least 30 seconds.
5. Turn the ignition switch to ON and turn the Techstream on [A].
6. Start the engine and idle it for 5 minutes or more [B].
7. With the vehicle stationary, depress the accelerator pedal and maintain an engine speed of 3000 rpm for 1 minute [C].
8. Idle the engine for 5 minutes or more [D].
9. Enter the following menus: Powertrain / Engine and ECT / Trouble Codes [E].
10. Read the DTCs.
HINT
* If a DTC is output, the system is malfunctioning.
* If a DTC is not output, perform the following procedure.
11. Enter the following menus: Powertrain / Engine and ECT / Utility / All Readiness.
12. Input the DTC: P0031, P0032, P0051 or P0052.
13. Check the DTC judgment result.
HINT
* If the judgment result shows NORMAL, the system is normal.
* If the judgment result shows ABNORMAL, the system has a malfunction.
* If the judgment result shows INCOMPLETE or UNKNOWN, perform steps [B] through [E] again.
14. If no pending DTC is output, perform a universal trip and check for permanent DTCs DTC Check / Clear.
HINT
* If a permanent DTC is output, the system is malfunctioning.
* If no permanent DTC is output, the system is normal.
WIRING DIAGRAM
Refer to DTC P2195 P2195.
INSPECTION PROCEDURE
NOTICE:
Inspect the fuses for circuits related to this system before performing the following inspection procedure.
HINT
* Read freeze frame data using the Techstream. Freeze frame data record 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.
* Bank 1 refers to the bank that includes the No. 1 cylinder*.
*: The No. 1 cylinder is the cylinder which is farthest from the transmission.
* Bank 2 refers to the bank that does not include the No. 1 cylinder.
* Sensor 1 refers to the sensor closest to the engine assembly.
* Sensor 2 refers to the sensor farthest away from the engine assembly.
* Refer to "Data List / Active Test" [A/F Heater Duty #1, A/F Heater Duty #2] Data List / Active List.
PROCEDURE
1. INSPECT AIR FUEL RATIO SENSOR (HEATER RESISTANCE)
(a) Disconnect the A/F sensor connector.
(b) Measure the resistance according to the value(s) in the table below.
Standard Resistance:
Bank 1 Sensor 1
Bank 2 Sensor 1
(c) Reconnect the A/F sensor connector.
NG -- REPLACE AIR FUEL RATIO SENSOR Removal
OK -- Continue to next step.
2. INSPECT AIR FUEL RATIO SENSOR HEATER RELAY
(a) Remove the A/F HEATER relay from the engine room relay block.
(b) Measure the resistance according to the value(s) in the table below.
Standard Resistance:
(c) Reinstall the A/F HEATER relay.
NG -- REPLACE AIR FUEL RATIO SENSOR HEATER RELAY
OK -- Continue to next step.
3. INSPECT ECM (HA1A OR HA2A VOLTAGE)
(a) Turn the ignition switch to ON.
(b) Measure the voltage between the terminals of the ECM connector.
Standard Voltage:
Result
HINT
* The HA1A means the A/F sensor bank 1 sensor 1.
* The HA2A means the A/F sensor bank 2 sensor 1.
B -- REPLACE ECM Removal
A -- Continue to next step.
4. CHECK HARNESS AND CONNECTOR (A/F SENSOR - ECM, A/F SENSOR - A/F HEATER RELAY)
(a) Check the harness and the connector between the ECM and the A/F sensor.
(1) Disconnect the A/F sensor connector.
(2) Disconnect the ECM connector.
(3) Measure the resistance according to the value(s) in the table below.
Standard Resistance (Check for Open):
Standard Resistance (Check for Short):
(4) Reconnect the A/F sensor connector.
(5) Reconnect the ECM connector.
(b) Check the harness and the connector between the A/F sensor and A/F HEATER relay.
(1) Disconnect the A/F sensor connector.
(2) Remove the A/F HEATER relay from the engine room relay block.
(3) Measure the resistance according to the value(s) in the table below.
Standard Resistance (Check for Open):
Standard Resistance (Check for Short):
(4) Reconnect the A/F sensor connector.
(5) Reinstall the A/F HEATER relay.
NG -- REPAIR OR REPLACE HARNESS OR CONNECTOR
OK -- REPLACE ECM Removal