I am trying to diagnose an engine cut out problem on a 2000 Chevy Malibu 3.1 engine. With the engine running, I disconnect the connector to the camshaft sensor. There is no change in engine performance and no check engine light. Shouldn’t I???
The camshaft position sensor sends a signal to the computer so it can fire the injectors at the proper time. Unpluging the camshaft position sensor with the engine idling won’t turn on the Check Engine light. This is because the OBDII engine management system must see this loss of camshaft position sensor signal input for at least 2 drive cycles before the computer will turn on the Check Engine light. But if you connect a scanner to vehicle, and look at the pending codes, you’ll find a code indicating a loss of camshaft position sensor signal input.
When the camshaft sensor is unplugged or it’s signal is lost, the computer goes to a default value for injector timing. You probably won’t see a differnce in engine operation at idle under this default value, but if the engine RPM’s are changed you’ll notice a difference in the engine operation.
A defective camshaft position sensor won’t cause the engine to cut out. But a defective crankshaft position sensor will.
Tester
Tester, thank you for your very informative response. I did hook up a scanner and there were no pending codes. But, even more importantly, in trying to reproduce my engine cutting out problem, I disconnected the crankshaft sensor. This did shut the engine down, but again, no check engine light. Is this the same issue with the 2 drive cycles?
The crankshaft position sensor is one of the primary inputs to the computer. So if it suddenly fails, the computer won’t see it as fault and turn on the Check Engine light. The computer just sees that there’s no crankshaft rotation and turns off the fuel pump, the injectors, and the secondary ignition.
The best way to find out if it’s the crankshaft position sensor is to start the engine, and either with a heat gun or hair drier heat up the sensor. If the engine cuts out it pretty much points to crank sensor.
Tester
Thanks again, I am currently running the engine with a multimeter connected to the crankshaft sensor to monitor voltage. I will get a hair dryer and try to help it along. Thank you for the input…