Note On Intermittents

If an intermittent Code 12 is being set, observe engine performance while manipulating the related wiring. Since Code 12 is a "no-start" condition, when the failure is induced, the engine should begin to stall. This will help to isolate the location of the malfunction.

If the crank signal circuit (circuit 6) is shorted to voltage at the ECM, the ECM will begin checking for distributor pulses and set Code 12 if the engine is not turning. As soon as the engine starts, Code 12 will become intermittent, however both "Service" telltale lights will remain on since the ECM thinks the engine is still cranking.