Throttle Full Close Switch: Testing and Inspection

The following tests are for the idle switch and full throttle switch only. The full throttle switch (normally open), closes only when the throttle valve is near the wide open position. The throttle valve potentiometer signal is used by the transmission control unit only and does not affect fuel or ignition system operation.

IDLE SWITCH CHECK

The idle switch is closed when the throttle valve is closed, and opens as soon as the throttle is opened.

1. Disconnect throttle valve harness connector from throttle valve switch/potentiometer housing.

Throttle Valve Switches And Potentiometer Connector Terminal ID:

CAUTION: The terminals on the harness connector are numbered in reverse order compared to the throttle valve potentiometer housing. Male tab #1 in throttle valve potentiometer connector inserts into the #6 female socket in the harness connector. Male tab #2 fits into socket #5, and so on. Be careful to check the correct terminals when testing.

2. Check for continuity between potentiometer terminals #6 and #4 (idle switch terminal and ground terminal respectively).

^ Should have continuity with throttle valve closed.

If not, loosen mounting screws and rotate potentiometer assembly (in the same direction as the throttle valve opens) just as much as is necessary to obtain continuity through the idle switch and tighten screws. If continuity cannot be obtained by adjustment, replace throttle valve switch/potentiometer assembly.

3. Insert a 0.012" (0.30mm) feeler gauge between idle stop and idle stop adjustment screw on throttle housing.

^ Should have no continuity (switch open) with feeler gauge inserted.

If not, open throttle by hand.

^ Resistance should go infinite (switch open).

If switch opens when throttle is opened, loosen mounting screws and rotate potentiometer assembly in the opposite direction as the throttle valve opens, then rotate back just as much as is necessary to obtain continuity through the idle switch. Tighten mounting screws and re-check idle switch.

If switch does not open, replace throttle valve switch/potentiometer assembly.

CIRCUIT CHECK


1. Check continuity between throttle valve harness connector terminals #1 & #2 and ECM terminals 52 & 53 respectively.

^ Should be continuous and not grounded.

If not OK, repair open or short in wiring.

2. Check continuity to ground between harness connector terminal #4 and engine block.

^ Should have continuity with not more than 0.2-0.5 ohms resistance.

If not, repair open in throttle switch ground wire.