Toyota Fortuner. Air Conditioning System (For Automatic Air Conditioning System) Vehicle Speed Signal Circuit

CHECK AIR CONDITIONING AMPLIFIER ASSEMBLY

CHECK HARNESS AND CONNECTOR (COMBINATION METER - AIR CONDITIONING AMPLIFIER)

AIR CONDITIONING SYSTEM (for Automatic Air Conditioning System) - Vehicle Speed Signal Circuit

DESCRIPTION

The air conditioning amplifier assembly monitors signals from the speedometer sensor via the combination meter assembly. The air conditioning amplifier assembly uses these signals to adjust the thermistor signal.

WIRING DIAGRAM

Toyota Fortuner. Ggn50, 60 Kun51, 61 Tgn51 Lan50.Air Conditioning.Air Conditioning System (For Automatic Air Conditioning System).Air Conditioning System (For Automatic Air Conditioning System) Vehicle Speed Signal Circuit

INSPECTION PROCEDURE

HINT:

Check that the speedometer in the combination meter assembly operates normally before inspecting the vehicle speed signal circuit (Toyota Fortuner RM0000011IY017X.html).

1.CHECK AIR CONDITIONING AMPLIFIER ASSEMBLY

Remove the air conditioning amplifier assembly with its connectors still connected (Toyota Fortuner RM000001K3A018X.html).

Using an oscilloscope, check the waveform of the air conditioning amplifier assembly.
Measurement Condition
Item
Content
Tester Connection
A38-9 (SPD) - Body ground
Tool Setting
5 V/DIV., 20 ms./DIV.
Condition
Driving at approximately 20 km/h (12 mph)
OK:
Waveform is as shown in the illustration.
Text in Illustration
*a
Component with harness connected
(Air Conditioning Amplifier Assembly)
HINT:
As the vehicle speed increases, the wavelength becomes shorter.

Measurement Condition
Item	Content
Tester Connection	A38-9 (SPD) - Body ground
Tool Setting	5 V/DIV., 20 ms./DIV.
Condition	Driving at approximately 20 km/h (12 mph)

Text in Illustration
*a	Component with harness connected (Air Conditioning Amplifier Assembly)

Go to step 2

PROCEED TO NEXT SUSPECTED AREA SHOWN IN PROBLEM SYMPTOMS TABLE (Toyota Fortuner RM0000045E300YX.html)

2.CHECK COMBINATION METER ASSEMBLY

Remove the combination meter assembly with its connector still connected (Toyota Fortuner RM000000THS01WX.html).

Using an oscilloscope, check the waveform of the combination meter assembly.
Measurement Condition
Item
Content
Tester Connection
C27-6 - Body ground
Tool setting
5 V/DIV., 20 ms./DIV.
Condition
Vehicle is driven at approximately 20 km/h (12 mph)
OK:
Waveform is as shown in the illustration.
Text in Illustration
*a
Component with harness connected
(Combination Meter Assembly)
HINT:
As the vehicle speed increases, the wavelength becomes shorter.

Measurement Condition
Item	Content
Tester Connection	C27-6 - Body ground
Tool setting	5 V/DIV., 20 ms./DIV.
Condition	Vehicle is driven at approximately 20 km/h (12 mph)

Text in Illustration
*a	Component with harness connected (Combination Meter Assembly)

REPLACE COMBINATION METER ASSEMBLY (Toyota Fortuner RM000000THS01WX.html)

OK

3.CHECK HARNESS AND CONNECTOR (COMBINATION METER - AIR CONDITIONING AMPLIFIER)

Disconnect the C27 combination meter assembly connector.

Disconnect the A38 air conditioning amplifier assembly connector.

Measure the resistance according to the value(s) in the table below.
Standard Resistance:
Tester Connection
Condition
Specified Condition
C27-6 - A38-9 (SPD)
Always
Below 1 Ω
A38-9 (SPD) - Body ground
Always
10 kΩ or higher

REPAIR OR REPLACE HARNESS OR CONNECTOR

REPLACE AIR CONDITIONING AMPLIFIER ASSEMBLY (Toyota Fortuner RM000001K3A018X.html)

Tester Connection	Condition	Specified Condition
C27-6 - A38-9 (SPD)	Always	Below 1 Ω
A38-9 (SPD) - Body ground	Always	10 kΩ or higher