Vehicle Speed Signal Circuit

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

Vehicle Speed Signal Circuit

DESCRIPTION

The A/C amplifier monitors signals from the speed sensor via the combination meter.
The A/C amplifier assembly uses these signals to revise the ambient temperature sensor signal.
Check that the speedometer in the combination meter operates normally before inspecting the vehicle speed signal circuit.
If the meter does not operate normally, refer to the combination meter system (How To Proceed With Troubleshooting).

WIRING DIAGRAM





INSPECTION PROCEDURE

PROCEDURE

1. INSPECT AIR CONDITIONING AMPLIFIER (SPD)





(a) Remove the A/C amplifier assembly with the connectors still connected.
(b) Move the shift lever to the Neutral position.
(c) Lift up the vehicle.
(d) Turn the ignition switch to the ON position.
(e) Connect the oscilloscope to terminal A32-2 (SPD) and body ground.
(f) Check the signal waveform according to the condition(s) in the table below.
OK:
Waveform operate as shown in the illustration.





HINT: As vehicle speed increases, the cycle of the signal waveform narrows.

NG -- CHECK HARNESS AND CONNECTOR (COMBINATION METER - AIR CONDITIONING AMPLIFIER)
OK -- PROCEED TO NEXT CIRCUIT INSPECTION SHOWN IN PROBLEM SYMPTOMS TABLE
2. CHECK HARNESS AND CONNECTOR (COMBINATION METER - AIR CONDITIONING AMPLIFIER)





(a) Measure the resistance according to the value(s) in the table below.
Standard resistance:





NG -- REPAIR OR REPLACE HARNESS OR CONNECTOR
OK -- GO TO COMBINATION METER SYSTEM