1994 Chevy Caprice aldl and idle

LUWILKES

MEMBER
1994 CHEVROLET CAPRICE
V8
2WD
AUTOMATIC
130,000 MILES

Check engine wont come on when terminal a and b is shorted but come on if not shorted and switch is on(normal). And fast start up idle all the time which is the reason I was trying to get a code by shorting the a and b terminal.

Wednesday, June 2nd, 2010 AT 11:24 PM

1 Reply

OBXAUTOMEDIC

MECHANIC
3,711 POSTS

Hello,

Ok, I am posting the proceedure and a diagram of the ALDL. Retry and see what happens.

Ground terminals A and B with the ignition "ON" and engine not running. The system will enter the diagnostic mode. In this mode, the computer will display a 12, three consecutive times, by flashing the "CHECK ENGINE", "SERVICE ENGINE SOON" or "MALFUNCTION INDICATOR LAMP" or light. A 12 consists of one flash, a short pause, then two flashes in rapid succession.

After 12 is displayed, any stored trouble s will be displayed by flashing the "CHECK ENGINE", "SERVICE ENGINE SOON" or "MALFUNCTION INDICATOR LAMP" light. All s are displayed 3 times each then a 12 will repeat. In the diagnostic mode, the computer will also energize all computer controlled relays and solenoids.

A possibility of the High Idle Problem could be a Vacuum Leak.