Diagnostic Aids

WARNING: This page is about a different car, the 2007 Saturn Vue. However, it is still accessible from the selected car via links, so may be relevant.

Inspect for the following conditions:

If the operation of the ignition system is intermittent, check for a reliable reference signal from the crankshaft position (CKP) sensor while cranking the engine. The PCM relies on the CKP sensor for engine reference. Without continuous accurate reference signals, there is no reliable spark or fuel injector pulse. The scan tool engine speed display should be more than 200 RPM while cranking. If erratic values, such as sudden spikes in engine speed are displayed, the engine reference signal may not be stable enough for the engine to start and run properly. Inspect the CKP sensor signal circuits for electromagnetic interference (EMI) or poor electrical connections.

A vehicle that starts and runs after being brought to the shop for an engine cranks but will not run concern, may have an ignition system that is susceptible to moisture. Spray water on the ignition system components and wiring in order to check for an engine miss or stall.

An intermittent malfunction may be caused by a condition in the ignition system electrical circuit. Inspect the wiring harness and components for an intermittent condition. Refer to Intermittent Conditions .