P0032
2UR-FSE ENGINE CONTROL SYSTEM: SFI SYSTEM: P0031,P0032,P0051,P0052: Oxygen (A/F) Sensor Heater Control Circuit Low (Bank 1 Sensor 1)
P0052 - Oxygen (A/F) Sensor Heater Control Circuit High (Bank 2 Sensor 1)
DESCRIPTION
HINT
- Although the DTC titles include 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.
The A/F sensor generates 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. 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
- 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 power 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 viewed from the rear of the engine assembly, Bank 1 is on the left side and Bank 2 is on the right side.
- Bank 1 refers to the bank that includes No. 1 cylinder.
- Bank 2 refers to the bank that does not include 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.
MONITOR DESCRIPTION
1. 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.
2. 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.
3. 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.
4. 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 the air-fuel ratio properly.
5. 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 or P0052 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 or P0051 is set.
MONITOR STRATEGY
TYPICAL ENABLING CONDITIONS
All:
P0031 and P0051:
P0032 and P0052:
TYPICAL MALFUNCTION THRESHOLDS
P0031 and P0051:
P0032 and P0052:
COMPONENT OPERATING RANGE
P0031 and P0051:
WIRING DIAGRAM
Refer to DTC P2195 P2195.
INSPECTION PROCEDURE
HINT
- When viewed from the rear of the engine assembly, Bank 1 is on the left side and Bank 2 is on the right side.
- Read freeze frame data using the Techstream. Freeze frame data records 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) Turn the power switch off.
(b) Disconnect the A/F sensor connector.
(c) Measure the resistance according to the value(s) in the table below.
Standard resistance:
for Bank 1 Sensor 1
for Bank 2 Sensor 1
NG -- REPLACE AIR FUEL RATIO SENSOR Removal
OK -- Continue to next step.
2. CHECK TERMINAL VOLTAGE (+B OF A/F SENSOR)
(a) Disconnect the A/F sensor connector.
(b) Turn the power switch on (IG).
(c) Measure the voltage according to the value(s) in the table below.
Standard voltage:
for Bank 1 Sensor 1
for Bank 2 Sensor 1
NG -- INSPECT FUSE (A/F)
OK -- Continue to next step.
3. CHECK HARNESS AND CONNECTOR (A/F SENSOR - ECM)
(a) Turn the power switch off.
(b) Disconnect the A/F sensor connector.
(c) Disconnect the E3 and E4 ECM connectors.
(d) Measure the resistance according to the value(s) in the table below.
Standard resistance (Check for open):
Standard resistance (Check for short):
NG -- REPAIR OR REPLACE HARNESS OR CONNECTOR
OK -- REPLACE ECM Removal
4. INSPECT FUSE (A/F)
(a) Remove the A/F fuse from the engine room No. 2 junction block.
(b) Measure the resistance according to the value(s) in the table below.
Standard resistance:
NG -- CHECK FOR SHORT IN ALL HARNESSES AND CONNECTORS CONNECTED TO FUSE AND REPLACE FUSE
OK -- Continue to next step.
5. INSPECT ENGINE ROOM NO. 2 JUNCTION BLOCK (A/F RELAY)
HINT
A/F relay cannot be removed and inspected, as it is part of the engine room No. 2 junction block internal circuit.
(a) Remove the terminal cover.
(b) Measure the voltage according to the value(s) in the table below.
Standard voltage:
NG -- REPLACE ENGINE ROOM NO. 2 JUNCTION BLOCK
OK -- Continue to next step.
6. CHECK HARNESS AND CONNECTOR (A/F FUSE - A/F SENSOR)
(a) Disconnect the A/F fuse from the engine room No. 2 junction block.
(b) Disconnect the E47*1 or E48*2 A/F sensor connector.
HINT
*1: for Bank 1 Sensor 1
*2: for Bank 2 Sensor 1
(c) Measure the resistance according to the value(s) in the table below.
Standard resistance (Check for open):
Standard resistance (Check for short):
NG -- REPAIR OR REPLACE HARNESS OR CONNECTOR
OK -- REPAIR OR REPLACE ENGINE ROOM NO. 2 JUNCTION BLOCK