Toyota 4Runner: Transmission Fluid Temperature Sensor "B" Circuit Low Input (P2742,P2743)

Toyota 4Runner Service Manual / Drivetrain / A750e Automatic Transmission / Transaxle / Automatic Transmission System / Transmission Fluid Temperature Sensor "B" Circuit Low Input (P2742,P2743)

DESCRIPTION

The Automatic Transmission Fluid (ATF) temperature sensor is on the transmission, just in front of the oil cooler inlet pipeline.

If the ECM detects an abnormally high ATF temperature near this sensor, it illuminates the warning light.

HINT:

The temperature of the ATF easily rises when towing, climbing hills, in traffic, etc.
If the ATF temperature sensor becomes short-circuited, the signal that indicates that the ATF temperature is 150°C (302°F) or higher is input into the ECM.

Vehicle conditions when the sensor is normal and when the sensor is short-circuited are indicated in the table below.

No. 2 ATF Temperature Sensor State	Detection Condition	Symptom	Recovery Condition
Sensor is normal	ATF temperature higher than 150°C (302°F)	ATF temperature warning light remains ON	ATF temperature below 135°C (275°F)*1
	ATF temperature higher than 130°C (266°F)	Shift point too high	ATF temperature below 110°C (230°F)
	Conditions (a) and (b) are met: (a) ATF temperature higher than 130°C (266°F) (b) Engine coolant temperature higher than 95°C (203°F)	Lock-up in 3rd gear*2	ATF temperature below 110°C (230°F)*1 and engine coolant temperature higher than 95°C (203°F)
Sensor is short-circuited	Any conditions	ATF temperature warning light blinks Shift point too high	Symptoms still occur
Sensor is short-circuited	Engine coolant temperature higher than 95°C (203°F)	Lock-up in 3rd gear*2	Symptoms still occur

HINT:

*1: When ATF temperature is in the normal range, it decreases to below 135°C (275°F) within 5 minutes with the shift lever in P or N in an idling state.

*2: When ATF temperature is normal, transmission lock-up occurs in 5th gear with the shift lever in D or with the S5 range selected, and in 4th gear with the S4 range selected.

DTC Code	DTC Detection Condition	Trouble Area
P2742	No. 2 ATF temperature sensor resistance is below 25 Ω (0.046 V) for 0.5 sec. or more (1-trip detection logic).	Short in No. 2 ATF temperature sensor circuit No. 2 ATF temperature sensor (Transmission wire) ECM
P2743	ATF temperature sensor resistance is higher than 156 kΩ (4.915 V) for 0.5 sec. or more and either condition is met (1-trip detection logic): (A) 15 min. or more have elapsed after the engine start when the engine coolant temperature or intake air temperature is -29.375°C (-20.875°F) or less. (B) 10 sec. or more have elapsed after the engine start when the engine coolant temperature and intake air temperature are higher than -29.375°C (-20.875°F).	Open in No. 2 ATF temperature sensor circuit No. 2 ATF temperature sensor (Transmission wire) ECM

DTC Code

DTC Detection Condition

Trouble Area

P2742

No. 2 ATF temperature sensor resistance is below 25 Ω (0.046 V) for 0.5 sec. or more (1-trip detection logic).

Short in No. 2 ATF temperature sensor circuit
No. 2 ATF temperature sensor (Transmission wire)
ECM

P2743

ATF temperature sensor resistance is higher than 156 kΩ (4.915 V) for 0.5 sec. or more and either condition is met (1-trip detection logic):

(A) 15 min. or more have elapsed after the engine start when the engine coolant temperature or intake air temperature is -29.375°C (-20.875°F) or less.

(B) 10 sec. or more have elapsed after the engine start when the engine coolant temperature and intake air temperature are higher than -29.375°C (-20.875°F).

Open in No. 2 ATF temperature sensor circuit
No. 2 ATF temperature sensor (Transmission wire)
ECM

MONITOR DESCRIPTION

The ATF temperature sensor converts the ATF temperature into an electrical resistance value. Based on the resistance, the ECM determines the ATF temperature, and the ECM detects an open or short in the ATF temperature circuit. If the resistance value of the ATF temperature sensor is below 25 Ω*1 or higher than 156 kΩ*2, the ECM interprets this as a fault in the ATF sensor or wiring. The ATF temperature warning light blinks and the ECM stores the DTC.

HINT:

*1: 150°C (302°F) or higher is indicated regardless of the actual ATF temperature.
*2: -40°C (-40°F) is indicated regardless of the actual ATF temperature.
The ATF temperature can be checked on the Techstream display.

WIRING DIAGRAM

Refer to DTC P0712 (See page ).

CAUTION / NOTICE / HINT

NOTICE:

Perform the universal trip to clear permanent DTCs (See page ).

1. DATA LIST

HINT:

Using the Techstream to read the Data List allows the values or states of switches, sensors, actuators and other items to be read without removing any parts. This non-intrusive inspection can be very useful because intermittent conditions or signals may be discovered before parts or wiring is disturbed. Reading the Data List information early in troubleshooting is one way to save diagnostic time.

NOTICE:

In the table below, the values listed under "Normal Condition" are reference values. Do not depend solely on these reference values when deciding whether a part is faulty or not.

(a) Warm up the engine.

(b) Turn the ignition switch off.

(d) Turn the ignition switch to ON.

(e) Turn the Techstream on.

(f) Enter the following menus: Powertrain / Engine and ECT / Data List.

(g) According to the display on the Techstream, read the Data List.

Engine and ECT

Tester Display	Measurement Item/Range	Normal Condition	Diagnostic Note
A/T Oil Temperature 2	No. 2 ATF temperature sensor value/ Min.: -40°C (-40°F) Max.: 215°C (419°F)	After stall test: Approximately 80°C (176°F) With engine cold: Equal to ambient temperature	If the value is -40°C (-40°F) or 215°C (419°F), the No. 2 ATF temperature sensor circuit is open or shorted.

Tester Display

Measurement Item/Range

Normal Condition

Diagnostic Note

A/T Oil Temperature 2

No. 2 ATF temperature sensor value/

Min.: -40°C (-40°F)

Max.: 215°C (419°F)

After stall test: Approximately 80°C (176°F)
With engine cold: Equal to ambient temperature

If the value is -40°C (-40°F) or 215°C (419°F), the No. 2 ATF temperature sensor circuit is open or shorted.

HINT:

When DTC P2742 is output and the Techstream output is 150°C (302°F) or higher, there is a short circuit.
When DTC P2743 is output and the Techstream output is -40°C (-40°F), there is an open circuit.
Check the temperature displayed on the Techstream in order to check if a malfunction exists.

Temperature Displayed	Malfunction
-40°C (-40°F)	Open circuit
150°C (302°F) or higher	Short circuit

PROCEDURE

1.	INSPECT TRANSMISSION WIRE (NO. 2 ATF TEMPERATURE SENSOR)

(a) Disconnect the B32 transmission wire connector.

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

Standard Resistance:

Tester Connection	Condition	Specified Condition
1 (OT2-) - 9 (OT2+)	Always	25 Ω to 156 kΩ
1 (OT2-) - Body ground	Always	10 kΩ or higher
9 (OT2+) - Body ground	Always	10 kΩ or higher

HINT:

If the resistance is out of the specified range at one of the ATF temperatures shown in the table below, the driveability of the vehicle may decrease.

Resistance (Reference):

ATF Temperature	Specified Condition
10°C (50°F)	5 to 8 kΩ
25°C (77°F)	2.5 to 4.5 kΩ
110°C (230°F)	0.22 to 0.28 kΩ

Text in Illustration

*a	Component without harness connected (Transmission Wire)

REPAIR OR REPLACE NO. 2 ATF TEMPERATURE SENSOR (TRANSMISSION WIRE)

2.	CHECK HARNESS AND CONNECTOR (TRANSMISSION WIRE - ECM)

(a) Disconnect the B37 and B38 ECM connectors.

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

Standard Resistance:

Tester Connection	Condition	Specified Condition
B38-11 (THO2) - B37-8 (ETHW)	Always	25 Ω to 156 kΩ
B38-11 (THO2) - Body ground	Always	10 kΩ or higher
B37-8 (ETHW) - Body ground	Always	10 kΩ or higher

Text in Illustration

*a	Rear view of wire harness connector (to ECM)

REPLACE ECM

REPAIR OR REPLACE HARNESS OR CONNECTOR

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