Toyota Tundra. Manual — part 1421



Air Fuel Ratio (A/F) sensor
(for bank 1, 2 sensor 1)



ECM

P2238
P2241



Case 1:

Condition (a) or (b) continues for 5.0 seconds or
more (1 trip detection logic):

a. AF+ voltage 0.5 V or less

b. (AF+) - (AF-) = 0.1 V or less



Case 2:

A/F sensor admittance: Less than 0.022 1/ohms (2
trip detection logic)



Open or short in A/F sensor
(for bank 1, 2 sensor 1) circuit



A/F sensor (for bank 1, 2
sensor 1)



A/F sensor heater (for bank 1,
2 sensor 1)



A/F relay



A/F sensor heater and relay
circuits



ECM

P2239
P2242

AF+ voltage more than 4.5 V for 5.0 seconds or more (2
trip detection logic)



Open or short in A/F sensor
(for bank 1,2 sensor 1) circuit



A/F sensor (for bank 1, 2
sensor 1)



A/F sensor heater (for bank 1,
2 sensor 1)



A/F relay



A/F sensor heater and relay
circuits



ECM

P2252
P2255

AF- voltage 0.5 V or less for 5.0 seconds or more (2 trip
detection logic)



Open or short in A/F sensor
(for bank 1,2 sensor 1) circuit



A/F sensor (for bank 1, 2
sensor 1)



A/F sensor heater (for bank 1,
2 sensor 1)



A/F relay



A/F sensor heater and relay
circuits



ECM

P2253
P2256

AF- voltage more than 4.5 V for 5.0 seconds or more (2
trip detection logic)



Open or short in A/F sensor
(for bank 1,2 sensor 1) circuit



A/F sensor (for bank 1, 2
sensor 1)



A/F sensor heater (for bank 1,
2 sensor 1)



A/F relay

2008 Toyota Tundra

2008 ENGINE PERFORMANCE Engine Control System (2UZ-FE) - Tundra

HINT:



DTCs P2237, P2238, P2239, P2252 and P2253 indicate malfunctions related to the bank 1 A/F sensor
circuit.



DTCs P2240, P2241, P2242, P2255 and P2256 indicate malfunctions related to the bank 2 A/F sensor
circuit.



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



Bank 2 refers to the bank that includes No. 2 cylinder.

MONITOR DESCRIPTION

These DTCs are output when there is an open or short in the A/F sensor circuit, or if A/F sensor output drops.

To detect these problems, the voltage of the A/F sensor is monitored when turning the ignition switch to the ON
position, and the admittance (admittance is an electrical term that indicates the ease of flow of current) is
checked while driving. If the voltage of the A/F sensor is between 0.6 V and 4.5 V, it is considered normal. If
the voltage is outside of the specified range, or the admittance is less than the standard value, the ECM will
determine that there is a malfunction in the A/F sensor. If the same malfunction is detected in the next driving
cycle, the MIL is illuminated and a DTC is set.

The Air-Fuel Ratio (A/F) sensor varies its output voltage in proportion to the air-fuel ratio. If the A/F sensor
impedance (alternating current resistance) or output voltage deviates greatly from the standard range, the ECM
determines that there is an open or short in the A/F sensor circuit.

MONITOR STRATEGY

MONITOR STRATEGY



A/F sensor heater and relay
circuits



ECM

Related DTCs

P2237: A/F sensor (for bank 1) open circuit between AF+ and AF-
P2238: A/F sensor (for bank 1) short circuit between AF+ and AF-
P2238: A/F sensor (for bank 1) short circuit between AF+ and
GND
P2238: A/F sensor (for bank 1) low impedance
P2239: A/F sensor (for bank 1) short circuit between AF+ and +B
P2240: A/F sensor (for bank 2) open circuit between AF+ and AF-
P2241: A/F sensor (for bank 2) short circuit between AF+ and AF-
P2241: A/F sensor (for bank 2) short circuit between AF+ and
GND
P2241: A/F sensor (for bank 1) low impedance
P2242: A/F sensor (for bank 2) short circuit between AF+ and +B
P2252: A/F sensor (for bank 1) short circuit between AF- and GND
P2253: A/F sensor (for bank 1) short circuit between AF- and +B
P2255: A/F sensor (for bank 2) short circuit between AF- and GND

2008 Toyota Tundra

2008 ENGINE PERFORMANCE Engine Control System (2UZ-FE) - Tundra

TYPICAL ENABLING CONDITIONS

All:

TYPICAL ENABLING CONDITIONS - ALL

A/F sensor - open circuit between AF+ and AF-

TYPICAL ENABLING CONDITIONS - A/F SENSOR - OPEN CIRCUIT BETWEEN AF+ AND AF-

A/F sensor - Low impedance

TYPICAL ENABLING CONDITIONS - A/F SENSOR - LOW IMPEDANCE

P2256: A/F sensor (for bank 2) short circuit between AF- and +B

Required Sensors/Components
(Main)

A/F sensor

Required Sensors/Components
(Related)

Engine Coolant Temperature (ECT) sensor, Crankshaft position
sensor

Frequency of Operation

Once per driving cycle

Duration

10 seconds: A/F sensor open circuit between AF+ and AF- and
Low impedance
5 seconds: Other

MIL Operation

2 driving cycles

Sequence of Operation

None

Monitor runs whenever following DTCs not present

P0031, P0032, P0051, P0052: A/F Sensor Heater
P0102 - P0103: MAF sensor
P0110 - P0113: IAT sensor
P0115 - P0118: ECT sensor
P0120 - P0223, P2135: TP sensor
P0125: Insufficient ECT for Closed Loop
P0171 -P0175: Fuel trim
P0300 - P0308: Misfire
P0335: CKP sensor
P0455 - P0456: EVAP system
P0500: VSS
P2440: AIR control valve stuck open
P2441: AIR control valve stuck close
P2444: Air pump stuck On
P2445: Air pump stuck Off

Battery voltage

11 V or higher

Engine

Running

Estimated sensor temperature

450 to 550°C (842 to 1022°F) for P2237 and P2240

Engine coolant temperature

0°C (32°F) or higher

Estimated sensor temperature

700 to 800°C (1292 to 1472°F) for P2238 and P2241

2008 Toyota Tundra

2008 ENGINE PERFORMANCE Engine Control System (2UZ-FE) - Tundra

Other:

TYPICAL ENABLING CONDITIONS - OTHER

TYPICAL MALFUNCTION THRESHOLDS

P2237 and P2240:

TYPICAL MALFUNCTION THRESHOLDS - P2237 AND P2240

P2238 and P2241:

TYPICAL MALFUNCTION THRESHOLDS - P2238 AND P2241

P2239 and P2242:

TYPICAL MALFUNCTION THRESHOLDS - P2239 AND P2242

P2252 and P2255:

TYPICAL MALFUNCTION THRESHOLDS - P2252 AND P2255

P2253 and P2256:

TYPICAL MALFUNCTION THRESHOLDS - P2253 AND P2256

WIRING DIAGRAM

Refer to DTC P2195 .

INSPECTION PROCEDURE

Fuel cut

Not executed

Battery voltage

11V or higher

Ignition switch

ON

Timing after ignition switch is OFF to ON

5 seconds or more

A/F sensor admittance

Below 0.002 1/ohms

When one of following conditions is met:

Condition 1, 2 or 3

1. Sensor admittance

Less than 0.022 1/ohms

2. AF+ voltage

0.5 V or less

3. Difference of AF+ and AF-

0.1 V or less

AF+ voltage

Higher than 4.5 V

AF- voltage

0.5 V or less

AF- voltage

Higher than 4.5 V

2008 Toyota Tundra

2008 ENGINE PERFORMANCE Engine Control System (2UZ-FE) - Tundra