P0032

1ZZ-FE ENGINE CONTROL SYSTEM: SFI SYSTEM: P0031: Oxygen Sensor Heater Control Circuit Low (Bank 1 Sensor 1)

DTC P0031 - Oxygen Sensor Heater Control Circuit Low (Bank 1 Sensor 1)

DTC P0032 - Oxygen Sensor Heater Control Circuit High (Bank 1 Sensor 1)

DESCRIPTION
The A/F sensor generates a voltage* that corresponds to the actual air-fuel ratio. This sensor voltage is used to provide the ECM with feedback so that it can control the air-fuel ratio. The ECM determines the deviation from the stoichiometric air-fuel ratio level, and regulates the fuel injection time. If the A/F sensor malfunctions, the ECM is unable to control the air-fuel ratio accurately.
The A/F sensor is the planar type and is integrated with the heater, which heats the solid electrolyte (zirconia element). This heater is controlled by the ECM. When the intake air volume is low (the exhaust gas temperature is low), a current flows into the heater to heat the sensor, in order to facilitate accurate oxygen concentration detection. In addition, the sensor and heater portions are narrower than the conventional type. The heat generated by the heater is conducted to the solid electrolyte though the alumina, therefore the sensor activation is accelerated.
In order to obtain a high purification rate of the carbon monoxide (CO), hydrocarbon (HC) and nitrogen oxide (NOx) components in the exhaust gas, a TWC is used. For the most efficient use of the TWC, the air-fuel ratio must be precisely controlled so that it is always close to the stoichiometric level.
*: Value changes inside the ECM. Since the A/F sensor is the current output element, a current is converted to a voltage inside the ECM. Any measurements taken at the A/F sensor or ECM connectors will show a constant voltage.

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 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.

HINT:
- When any of these DTCs are set, check the A/F sensor voltage output by selecting the following menu items on Techstream: Powertrain / Engine and ECT / Data List / A/F Control System / AFS B1 S1.
- Short-term fuel trim values can also be read using Techstream.
- The ECM regulates the voltage at the A1A+ and A1A- terminals of the ECM at a constant level. Therefore, the A/F sensor voltage output cannot be confirmed without using Techstream.
- An OBD II scan tool displays the A/F sensor voltage output at a voltage level that is 1/5 of that of the Techstream.

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 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 the 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 will be inaccurate, as a result, the ECM will be 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

P0031:

P0032:

TYPICAL MALFUNCTION THRESHOLDS

P0031:

P0032:

COMPONENT OPERATING RANGE

MONITOR RESULT

The monitor result (mode 6) allows the OBD scan tool to display the monitor status, test value and test limit.
A problem in this component can be found by comparing the test value and test limit. This procedure is described in "CHECKING MONITOR STATUS" (Mode 6 Data).

- TID (Test Identification) is assigned to each emission-related component.
- TLT (Test Limit Type):
If TLT is 0, the component is malfunctioning when the test value is higher than the test limit.
If TLT is 1, the component is malfunctioning when the test value is lower than the test limit.
- CID (Component Identification) is assigned to each test value.
- Unit Conversion is used to calculate the test value indicated on generic OBD scan tools.

TID $07: A/F Heater

WIRING DIAGRAM

INSPECTION PROCEDURE

HINT: 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 A24 Air-Fuel Ratio (A/F) sensor connector.
(b) Measure the resistance between the terminals of the A/F sensor connector.
Standard resistance:

(c) Reconnect the A/F sensor connector.
NG -- REPLACE AIR FUEL RATIO SENSOR
OK -- Continue to next step.
2. INSPECT EFI RELAY

(a) Remove the EFI relay from the engine room R/B.
(b) Check the EFI relay resistance.
Standard resistance:

(a) Turn the ignition switch to the ON position.
(b) Measure the voltage between the terminals of the E4 ECM connector.
Standard voltage:

OK -- REPLACE ECM
NG -- Continue to next step.
4. CHECK HARNESS AND CONNECTOR (AIR FUEL RATIO SENSOR - ECM, EFI RELAY)

(a) Check the harness and connector between the ECM and A/F sensor.
(1) Disconnect the A24 A/F sensor connector.
(2) Disconnect the E4 ECM connector.
(3) Check the resistance.
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 connector between the A/F sensor and EFI relay.
(1) Inspect the EFI2 fuse.

- Remove the EFI2 fuse from the engine room R/B.
- Check the EFI2 fuse resistance.
Standard resistance:
Below 1 Ohms
- Reinstall the EFI2 fuse.

(2) Disconnect the A24 A/F sensor connector.
(3) Remove the EFI relay from the engine room R/B.
(4) Check the resistance.
Standard resistance (Check for open):

Standard resistance (Check for short):

(5) Reconnect the A/F sensor connector.
(6) Reinstall the EFI relay.
NG -- REPAIR OR REPLACE HARNESS OR CONNECTOR
OK -- REPLACE ECM