P0031
2ZR-FE ENGINE CONTROL: SFI SYSTEM: P0031,P0032: Oxygen (A/F) Sensor Heater Control Circuit Low (Bank 1 Sensor 1)
DESCRIPTION
Refer to DTC P2195 P2195.
HINT
- When either of these DTCs is set, the ECM enters fail-safe mode. The ECM turns off the air fuel ratio sensor heater in fail-safe mode. Fail-safe mode continues until the ignition switch is turned off.
- Although the DTC titles say the oxygen sensor, these DTCs relate to the air fuel ratio sensor.
- Sensor 1 refers to the sensor mounted in front of the Three-way catalytic converter and located near the engine assembly.
- The ECM uses pulse width modulation to adjust the current through the heater. The air fuel ratio sensor heater circuit uses a relay on the +B side of the circuit.
HINT
- 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 ECM uses information from the air fuel ratio 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 to purify the exhaust gases.
The air fuel ratio 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 air fuel ratio 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 air fuel ratio sensor becomes inaccurate, as a result, the ECM is unable to regulate air fuel ratio properly.
When the current in the air fuel ratio 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
All:
P0031
P0031:
P0032
P0032:
TYPICAL MALFUNCTION THRESHOLDS
P0031
P0031:
P0032
P0032:
COMPONENT OPERATING RANGE
WIRING DIAGRAM
Refer to DTC P2195 P2195.
INSPECTION PROCEDURE
HINT
Read freeze frame data using the 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 AIR FUEL RATIO SENSOR (HEATER RESISTANCE)
(a) Disconnect the air fuel ratio sensor connector.
(b) Measure the resistance according to the value(s) in the table below.
Standard Resistance:
(c) Reconnect the air fuel ratio sensor connector.
NG -- REPLACE AIR FUEL RATIO SENSOR Removal
OK -- Continue to next step.
2. CHECK TERMINAL VOLTAGE (POWER SOURCE)
(a) Disconnect the air fuel ratio sensor connector.
(b) Turn the ignition switch to ON.
(c) Measure the voltage according to the value(s) in the table below.
Standard Voltage:
(d) Reconnect the air fuel ratio sensor connector.
NG -- INSPECT FUSE (EFI NO. 2 FUSE)
OK -- Continue to next step.
3. CHECK HARNESS AND CONNECTOR (AIR FUEL RATIO SENSOR - ECM)
(a) Disconnect the air fuel ratio sensor connector.
(b) Disconnect the ECM connector.
(c) Measure the resistance according to the value(s) in the table below.
Standard Resistance (Check for Open):
Standard Resistance (Check for Short):
(d) Reconnect the air fuel ratio sensor connector.
(e) Reconnect the ECM connector.
NG -- REPAIR OR REPLACE HARNESS OR CONNECTOR (AIR FUEL RATIO SENSOR - ECM)
OK -- Continue to next step.
4. CHECK WHETHER DTC OUTPUT RECURS (DTC P0031 OR P0032)
(a) Connect the Techstream to the DLC3.
(b) Turn the ignition switch to ON.
(c) Turn the Techstream on.
(d) Clear DTCs DTC Check / Clear.
(e) Start the engine.
(f) Allow the engine to idle for 1 minute or more.
(g) Enter the following menus: Powertrain / Engine and ECT / Trouble Codes.
(h) Read the DTCs.
Result:
B -- REPLACE ECM Removal
A -- CHECK FOR INTERMITTENT PROBLEMS Check for Intermittent Problems
5. INSPECT FUSE (EFI NO. 2 FUSE)
(a) Remove the EFI No. 2 fuse from the engine room relay block.
(b) Measure the resistance according to the value(s) in the table below.
Standard Resistance:
(c) Reinstall the EFI No. 2 fuse.
NG -- REPLACE FUSE (EFI NO. 2)
OK -- REPAIR OR REPLACE HARNESS OR CONNECTOR (INTEGRATION RELAY (EFI MAIN RELAY) - AIR FUEL RATIO SENSOR)