Toyota FJ Cruiser (GSJ 10, 15 series). Instruction - part 32

1GR-FE ENGINE CONTROL SYSTEM  –  SFI SYSTEM

ES–83

ES

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 (See page 

ES-307

).

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.

DTC

P0031

Oxygen (A/F) Sensor Heater Control Circuit 
Low (Bank 1 Sensor 1)

DTC

P0032

Oxygen (A/F) Sensor Heater Control Circuit 
High (Bank 1 Sensor 1)

DTC

P0051

Oxygen (A/F) Sensor Heater Control Circuit 
Low (Bank 2 Sensor 1)

DTC

P0052

Oxygen (A/F) Sensor Heater Control Circuit 
High (Bank 2 Sensor 1)

DTC No.

DTC Detection Conditions

Trouble Areas

P0031
P0051

Air-Fuel Ratio (A/F) sensor heater current less than 0.8 A (1 
trip detection logic)

•

Open in A/F sensor heater circuit

•

A/F sensor heater

•

A/F sensor heater relay

•

ECM

Reference (System Diagram of Bank 1 Sensor 1):

From 
Battery

From EFI 
Relay

A/F HEATER

A/F HEATER

A/F Sensor

ECM

+B

A1A-

Sensor

Heater

A1A+

HA1A

A1A+

A1A-

HA1A

Duty 
Control

A133442E01

ES–84

1GR-FE ENGINE CONTROL SYSTEM  –  SFI SYSTEM

ES

HINT:
•

Bank 1 refers to the bank that includes cylinder No. 1.

•

Bank 2 refers to the bank that does not include cylinder No. 1.

•

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 (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 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 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
P0052

Air-Fuel Ratio (A/F) sensor heater current more than 10 A (1 
trip detection logic)

•

Short in A/F sensor heater circuit

•

A/F sensor heater

•

A/F sensor heater relay

•

ECM

Related DTCs

P0031: A/F sensor heater (bank 1) open/short (Low electrical current)
P0032: A/F sensor heater (bank 1) open/short (High electrical current)
P0051: A/F sensor heater (bank 2) open/short (Low electrical current)
P0052: A/F sensor heater (bank 2) open/short (High electrical current)

Required Sensors/Components (Main)

A/F sensor heater (bank 1 and 2)

Required Sensors/Components (Related)

-

Frequency of Operation

Continuous

Duration

10 seconds

MIL Operation

Immediate

Sequence of Operation

None

Monitor runs whenever following DTCs not present

None

Battery voltage

10.5 V or more

A/F sensor heater duty-cycle ratio

50 % or more

Time after engine start

10 seconds or more

DTC No.

DTC Detection Conditions

Trouble Areas

1GR-FE ENGINE CONTROL SYSTEM  –  SFI SYSTEM

ES–85

ES

P0032 and P0052:

TYPICAL MALFUNCTION THRESHOLDS

P0031 and P0051:

P0032 and P0052:

COMPONENT OPERATING RANGE

WIRING DIAGRAM

Refer to DTC P2195 (See page 

ES-312

).

INSPECTION PROCEDURE

HINT:
Read freeze frame data using an intelligent tester. 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.

(a) Disconnect the B33*1 or B31*2 A/F sensor connector.

HINT:
•

*1: Bank 1 Sensor 1

•

*2: Bank 2 Sensor 1

(b) Measure the resistance between the terminals of the A/F 

sensor connector.
Standard Resistance (Bank 1 Sensor 1)

Standard Resistance (Bank 2 Sensor 1)

(c) Reconnect the A/F sensor connector.

NG

OK

Time after engine start

10 seconds or more

A/F sensor heater current

Less than 0.8 A

A/F sensor heater current

More than 10 A

A/F sensor heater resistance

1.8 to 3.4 

Ω at 20°C (68°F)

1

INSPECT AIR FUEL RATIO SENSOR (HEATER RESISTANCE)

Component Side:

A/F Sensor

+B

A1A- *1 
A2A- *2

*1: Bank 1 
*2: Bank 2

*2

B31

*1

B33

Front View

A1A+ *1 
A2A+ *2

HA1A *1 
HA2A *2

A085152E57

Tester Connections

Specified Conditions

HA1A (1) - +B (2)

1.8 to 3.4 

Ω at 20°C (68°F)

HA1A (1) - A1A- (4)

10 k

Ω or higher

Tester Connections

Specified Conditions

HA2A (1) - +B (2)

1.8 to 3.4 

Ω at 20°C (68°F)

HA2A (1) - A2A- (4)

10 k

Ω or higher

REPLACE AIR FUEL RATIO SENSOR (See 
page 

EC-21

)

ES–86

1GR-FE ENGINE CONTROL SYSTEM  –  SFI SYSTEM

ES

(a) Remove the A/F sensor heater relay from the engine 

room relay block.

(b) Check the A/F sensor heater relay resistance.

Standard Resistance

(c) Reinstall the A/F sensor heater relay.

NG

OK

(a) Turn the ignition switch ON.
(b) Measure the voltage between the terminals of the B2 

ECM connector.
Standard Voltage

HINT:
•

The HA1A means the A/F sensor bank 1 sensor 1.

•

The HA2A means the A/F sensor bank 2 sensor 1.

OK

NG

2

INSPECT AIR FUEL RATIO SENSOR HEATER RELAY

B016200E02

Tester Connections

Specified Conditions

3 - 5

10 k

Ω or higher

Below 1 

Ω

(when battery voltage applied to terminals 1 and 2)

REPLACE AIR FUEL RATIO SENSOR 
HEATER RELAY

3

INSPECT ECM (HA1A OR HA2A VOLTAGE)

E04

E05

HA1A

HA2A

ECM Connector

B2

A115970E14

Tester Connections

Specified Conditions

HA1A (B2-2) - E04 (B2-7)

11 to 14 V

HA2A (B2-1) - E05 (B2-6)

REPLACE ECM (See page 

ES-446

)