Using The Iac Signal Tester Alone; Checking The Iac Circuit. - OTC 3052S Parts List & Operating Instructions

Parts List & Operating Instructions

Using The IAC Signal Tester Alone

1. Disconnect the vehicle wiring harness from the IAC on
the throttle body.
2. Connect the signal tester to the vehicle wiring harness.

Checking The IAC Circuit.

If you are using only the IAC signal tester, you must do two things:
check the circuit when there is a demand for a larger amount of air
through the IAC valve, and check the circuit when there is a demand
for a smaller amount of air through the IAC valve. This procedure
tells how:
1. Create a demand for large amounts of air to be passed through the IAC valve. To do this, create a load
on the engine at idle either by turning the Air Conditioning on, or by turning the front wheel completely
to the left or right until it locks.
2. The increase in load will cause the engine RPM to decrease. Then the ECM should begin sending
signals to the IAC to change the position of the pintle to allow more air to pass through it.
3. If the ECM is sending the signal to the IAC as described above, both LEDs on the signal tester should
be lit. Color is not important.
4. If either light is not lit, inspect the circuit between the ECM and the IAC harness connector for broken
wires or poor connections. If all wires and connections are good, the ECM may be defective.
5. Create a demand for less air to pass through the IAC valve by creating a vacuum leak to the intake
manifold.
6. When a leak is large enough, the RPM should begin to increase. The ECM should begin sending
signals to the IAC to change the position of the pintle to reduce the amount of air passing through it.
7. If the ECM is sending the signal to the IAC as described above, both LEDs on the signal tester should
be lit. Color is not important.
8. If both lights flash and the IAC does not respond to the signals from the ECM (while hooked to the
vehicle wiring harness), the IAC valve may be defective. If either light is not lit, inspect the circuit
between the ECM and the IAC harness connector for broken wires or poor connections. If all wires
and connections are good, the ECM may be defective.
Form No. 103378, Sheet 1 of 1, Back