Toyota Tundra. Manual — part 1157

HINT:



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.



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.



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.

Fig. 40: Oxygen (A/F) Sensor Heater Control Circuit Diagram

DTC TROUBLE DETECTION CONDITION CHART

DTC

No.

DTC Detection Condition

Trouble Area

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 (sensor
1)



Integration relay (A/F
relay)



ECM

P0032
P0052

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



Short in A/F sensor heater
circuit



A/F sensor heater (sensor
1)



Integration relay (A/F
relay)

2008 Toyota Tundra

2008 ENGINE PERFORMANCE Engine Control System (1GR-FE) - Tundra

HINT:



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

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.

MONITOR STRATEGY

MONITOR STRATEGY



ECM

Related DTCs

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

Required Sensors/Components (Main)

A/F sensor heater

Required Sensors/Components (Related) -
Frequency of Operation

Continuous

Duration

10 seconds

MIL Operation

Immediate

Sequence of Operation

None

2008 Toyota Tundra

2008 ENGINE PERFORMANCE Engine Control System (1GR-FE) - Tundra

TYPICAL ENABLING CONDITIONS

All:

TYPICAL ENABLING CONDITIONS

P0031 and P0051:

TYPICAL ENABLING CONDITIONS

P0032 and P0052:

TYPICAL ENABLING CONDITIONS

TYPICAL MALFUNCTION THRESHOLDS

P0031 and P0051:

TYPICAL MALFUNCTION THRESHOLDS

P0032 and P0052:

TYPICAL MALFUNCTION THRESHOLDS

COMPONENT OPERATING RANGE

COMPONENT OPERATING RANGE

WIRING DIAGRAM

Refer to DTC P2195 .

INSPECTION PROCEDURE

HINT:

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

Battery voltage

Less than 20 V

Engine

Running

A/F sensor heater current

Less than 0.8 A

Hybrid IC high current limiter port

Fail

A/F sensor heater resistance

1.8 to 3.4 ohms at 20°C (68°F)

2008 Toyota Tundra

2008 ENGINE PERFORMANCE Engine Control System (1GR-FE) - Tundra

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.

1. INSPECT AIR FUEL RATIO SENSOR (HEATER RESISTANCE)

a. Disconnect the D33*1 or D34*2 A/F sensor connector.

b. Measure the resistance according to the value(s) in the table below.

Standard resistance (for Bank 1 sensor 1)

TESTER CONNECTION SPECIFIED CONDITION

Standard resistance (for Bank 2 sensor 1)

TESTER CONNECTION SPECIFIED CONDITION

NG : REPLACE AIR FUEL RATIO SENSOR (See REMOVAL )

Fig. 41: Identifying Air Fuel Ratio Sensor Connector Terminals

OK : Go to next step

2. CHECK TERMINAL VOLTAGE (+B OF A/F SENSOR)

a. Disconnect the D33*1 or D34*2 A/F sensor connector.

Tester Connection Condition Specified Condition

1 (HA1A) - 2 (+B) 20°C (68°F)

1.8 to 3.4 ohms

1 (HA1A) - 4(A1A-)

Always

10 kohms or higher

Tester Connection

Condition Specified Condition

1 (HA2A) - 2 (+B) 20°C (68°F)

1.8 to 3.4 ohms

1 (HA2A) - 4 (A2A-)

Always

10 kohms or higher

2008 Toyota Tundra

2008 ENGINE PERFORMANCE Engine Control System (1GR-FE) - Tundra