Toyota Tundra. Manual — part 2421

The No. 1 cooler thermistor (evaporator temperature sensor) is installed on the evaporator in the air conditioner
unit to detect the cooled air temperature that has passed through the evaporator and control the air conditioning.
It sends appropriate signals to the air conditioning amplifier. The resistance of the No. 1 cooler thermistor
(evaporator temperature sensor) changes in accordance with the cooled air temperature that has passed through
the evaporator. As the temperature decreases, the resistance increases. As the temperature increases, the
resistance decreases.

The air conditioning amplifier applies voltage (5 V) to the No. 1 cooler thermistor (evaporator temperature
sensor) and reads voltage changes as the resistance of the No. 1 cooler thermistor (evaporator temperature
sensor) changes. This sensor is used for frost prevention.

DTC DETECTION CONDITION CHART

WIRING DIAGRAM

Fig. 110: Evaporator Temperature Sensor - Wiring Diagram
Courtesy of TOYOTA MOTOR SALES, U.S.A., INC.

INSPECTION PROCEDURE

1. READ VALUE USING TECHSTREAM (EVAPORATOR FIN THERMISTOR)

a. Use the Data List to check if the evaporator fin thermistor is functioning properly.

Air Conditioner

DTC

DTC Detection Condition

Trouble Area

B1413/13

Open or short in evaporator
temperature sensor circuit



No. 1 cooler thermistor
(evaporator temperature
sensor)



Air conditioning harness



Air conditioning amplifier

2009 Toyota Tundra

2009 HVAC Air Conditioning - Tundra

DATA LIST

OK:

The display is as specified in the normal condition.

Result

RESULT REFERENCE

B: PROCEED TO NEXT CIRCUIT INSPECTION SHOWN IN PROBLEM SYMPTOMS
TABLE (See PROBLEM SYMPTOMS TABLE )

C: REPLACE AIR CONDITIONING AMPLIFIER (See REMOVAL )

A: Go to Next Step

2. INSPECT NO. 1 COOLER THERMISTOR (EVAPORATOR FIN THERMISTOR)

Fig. 111: Temperature And Resistance Graph
Courtesy of TOYOTA MOTOR SALES, U.S.A., INC.

a. Remove the No. 1 cooler thermistor (evaporator temperature sensor) connector (see

DISASSEMBLY ).

Tester Display

Measurement Item/Range

Normal Condition

Diagnostic Note

Evaporator Fin

Thermistor

Evaporator fin
thermistor/Min.:-29.7°C (-
21.46°F)
Max.: 59.55°C (139.19°F)

Actual evaporator
temperature is displayed

Open in circuit: -
29.7°C (-21.46°F)
Short in circuit:
59.55°C (139.19°F)

Result

Proceed to

NG

A

OK (Checking from the PROBLEM SYMPTOMS TABLE)

B

OK (Checking from the DTC)

C

2009 Toyota Tundra

2009 HVAC Air Conditioning - Tundra

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

Standard Resistance

TESTER CONNECTION SPECIFIED CONDITION CHART

HINT:

As the temperature increases, the resistance decreases (see the graph ).

NG: REPLACE NO. 1 COOLER THERMISTOR (EVAPORATOR FIN THERMISTOR)
(See DISASSEMBLY )

OK: Go to Next Step

3. REPAIR OR REPLACE AIR CONDITIONING HARNESS

a. Repair or replace the air conditioning harness.

4. CHECK FOR DTC

a. Clear the DTC (see DTC CHECK/CLEAR ).

b. Check for DTC (see DTC CHECK/CLEAR ).

OK:

DTC is not output.

NG: REPLACE AIR CONDITIONING AMPLIFIER (See REMOVAL )

OK: END

Tester Connection Condition Specified Condition

1 - 2

-10°C (14°F) 7.30 to 9.10 kohms

-5°C (23°F) 5.65 to 6.95 kohms

0°C (32°F)

4.40 to 5.35 kohms

5°C (41°F)

3.40 to 4.15 kohms

10°C (50°F) 2.70 to 3.25 kohms
15°C (59°F) 2.14 to 2.58 kohms
20°C (68°F) 1.71 to 2.05 kohms
25°C (77°F) 1.38 to 1.64 kohms
30°C (86°F) 1.11 to 1.32 kohms

NOTE:



Even slightly touching the sensor may change the resistance
value. Be sure to hold the connector of the sensor.



When measuring, the sensor temperature must be the same as
the ambient temperature.

2009 Toyota Tundra

2009 HVAC Air Conditioning - Tundra

DTC B1422/22 COMPRESSOR LOCK SENSOR CIRCUIT

DESCRIPTION

The ECM sends a engine speed signal to the air conditioning amplifier via the CAN communication system.

The air conditioning amplifier reads the difference between compressor speed and engine speed. When the
difference becomes too large, the air conditioning amplifier determines that the compressor locks, and turns the
magnetic clutch off.

DTC DETECTION CONDITION CHART

WIRING DIAGRAM

Fig. 112: Compressor Lock Sensor - Wiring Diagram
Courtesy of TOYOTA MOTOR SALES, U.S.A., INC.

INSPECTION PROCEDURE

DTC

DTC Detection Condition

Trouble Area

B1422/22

Open or short in compressor lock
sensor circuit



Air conditioning compressor
(lock sensor)



Compressor drive belt



Harness and connector
between air conditioning
compressor (lock sensor) and
air conditioning amplifier



Air conditioning amplifier



CAN communication system

2009 Toyota Tundra

2009 HVAC Air Conditioning - Tundra