Throttle Full Open Switch: Testing and Inspection

Motronic ECU Harness Connector (pin # Locations):

1. With ignition turned "on", disconnect throttle switch, and check voltage between terminals #1 and #2, and between terminals #3 and #2 of harness side of connector. Should be battery voltage. If not, check for:

a. Open or grounded circuit between throttle switch harness connector terminal #1 and ECU terminal #28.
b. Open or grounded circuit between throttle switch harness connector terminal #3 and ECU terminal #31.
c. Open circuit between throttle switch connector terminal #2 and ground.

If no wiring problems are found and there is still no power at terminals #1 or #3 of harness side connector, then there is a poor connection at the ECU or the ECU is faulty.

2. Connect ohmmeter between terminals #1 and #2 of switch side of connector.

3. Open throttle about half way and close slowly, while observing the resistance.
- Resistance should be infinite (idle switch open) while throttle is open and then go to zero (idle switch closed) when throttle stop is within approx. 0.7mm (0.028") of idle stop adjustment screw.

4. Connect ohmmeter between terminals #3 and #2 of switch side of connector.
- .Resistance should be infinite (open circuit).

5. Slowly open throttle all the way.
- .Resistance should remain infinite and then go to zero when throttle is within approx. 10~ of full throttle stop. Adjust position of full throttle switch if necessary.