P0032
1NZ-FE ENGINE CONTROL SYSTEM: SFI SYSTEM: P0031,P0032: Oxygen (A/F) Sensor Heater Control Circuit Low (Bank 1 Sensor 1)
DESCRIPTION
Refer to DTC P2195 P2195.
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.
- When either 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 to 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.
Example:
The ECM sets DTC P0032 when the current in the A/F sensor heater is more than 10 A. Conversely, when the heater current is less than 0.8 A, DTC P0031 is set.
MONITOR STRATEGY
TYPICAL ENABLING CONDITIONS
All:
All::
P0031:
P0031::
P0032:
P0032::
TYPICAL MALFUNCTION THRESHOLDS
P0031:
P0031::
P0032:
P0032::
COMPONENT OPERATING RANGE
CONFIRMATION DRIVING PATTERN
- Connect the Techstream to the DLC3.
- Turn the ignition switch to ON and turn the Techstream on.
- Clear DTCs (even if no DTCs are stored, perform the clear DTC operation).
- Turn the ignition switch off and wait for at least 30 seconds.
- Turn the ignition switch to ON and turn the Techstream on [A].
- Start the engine and idle it for 5 minutes or more [B].
- With the vehicle stationary, depress the accelerator pedal and maintain an engine speed of 3000 rpm for 1 minute [C].
- Idle the engine for 5 minutes or more [D].
- Enter the following menus: Powertrain / Engine and ECT / Trouble Codes [E].
- Read pending DTCs.
HINT
- If a pending DTC is output, the system is malfunctioning.
- If a pending DTC is not output, perform the following procedure.
- Enter the following menus: Powertrain / Engine and ECT / Utility / All Readiness.
- Input the DTC: P0031 or P0032.
- Check the DTC judgment result.
- If the judgment result shows INCOMPLETE or UNKNOWN, perform steps [B] through [E] again.
- 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
HINT
Read freeze frame data using a 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.
PROCEDURE
1. INSPECT AIR-FUEL RATIO SENSOR (HEATER RESISTANCE)
(a) Disconnect the C23 A/F sensor connector.
(b) Measure the resistance of the A/F sensor connector.
Standard resistance:
(c) Reconnect the A/F sensor connector.
NG -- REPLACE AIR-FUEL RATIO SENSOR Removal
OK -- Continue to next step.
2. CHECK TERMINAL VOLTAGE (+B OF A/F SENSOR)
(a) Disconnect the C23 A/F sensor connector.
(b) Turn the ignition switch to ON.
(c) Measure the voltage between the terminals of the C23 A/F sensor connector and body ground.
Standard voltage:
(d) Reconnect the A/F sensor connector.
OK -- CHECK HARNESS AND CONNECTOR (A/F SENSOR - ECM)
NG -- Continue to next step.
3. INSPECT INTEGRATION RELAY (EFI RELAY)
(a) Remove the integration relay from the engine room relay block.
(b) Inspect the EFI fuse.
(1) Remove the EFI fuse from the integration relay.
(2) Measure the EFI fuse resistance.
Standard resistance:
Below 1 Ohms
(3) Reinstall the EFI fuse.
(c) Inspect the EFI relay.
(1) Measure the EFI relay resistance.
Standard resistance:
(d) Reinstall the integration relay.
NG -- REPLACE INTEGRATION RELAY
OK -- Continue to next step.
4. CHECK HARNESS AND CONNECTOR (A/F SENSOR - EFI RELAY)
(a) Disconnect the C23 A/F sensor connector.
(b) Remove the integration relay from the engine room Relay Block (R/B).
(c) Check the resistance.
Standard resistance (Check for open):
Standard resistance (Check for short):
(d) Reconnect the A/F sensor connector.
(e) Reinstall the integration relay.
NG -- REPAIR OR REPLACE HARNESS OR CONNECTOR
OK -- CHECK ECM POWER SOURCE CIRCUIT Component Tests and General Diagnostics
5. CHECK HARNESS AND CONNECTOR (A/F SENSOR - ECM)
(a) Disconnect the C23 A/F sensor connector.
(b) Disconnect the C20 ECM connector.
(c) Check the resistance.
Standard resistance (Check for open):
Standard resistance (Check for short):
(d) Reconnect the A/F sensor connector.
(e) Reconnect the ECM connector.
NG -- REPAIR OR REPLACE HARNESS OR CONNECTOR
OK -- Continue to next step.
6. 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) Drive the vehicle in accordance with the driving pattern described in the Confirmation Driving Pattern.
(f) Read DTCs.
Result:
B -- REPLACE ECM Removal
A -- CHECK FOR INTERMITTENT PROBLEMS