There's three separate systems. The ignition coil / spark plugs, the fuel pump, and the trigger circuit that tells the Engine Computer to turn both of them on. The coil circuit is the least likely one to have a problem. Most problems occur in the trigger circuit which is the cam and crank sensors.
The fastest way to tell if the two sensors are working is by viewing live sensor data on a scanner. If you don't have a scanner, you can see the results of the computer turning the systems on by measuring the voltage feeding them. The voltage comes from the automatic shutdown (ASD) relay when the computer gets pulses from those two sensors.
Look for a dark green / orange wire in the connector for a coil or injector and measure the voltage on it. You should see full battery voltage for one second after turning on the ignition switch, then it should come back during engine rotation, (cranking or running). If it doesn't come back during cranking, check the two sensors for a 5.0 volt feed and a good ground which should measure close to 0.2 volts. Normally if those voltages are correct but one of the sensors isn't working, it should set a diagnostic fault code and the computer will turn on the Check Engine light. When there's no code, you'll need a scanner to see which sensor isn't producing a signal.
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Friday, December 24th, 2010 AT 6:01 PM
