This Chevy Spark came in with oil leaks and all kinds of engine problems. After the engine was removed and oil leaks were fixed etc we start the engine and notes the engine light came on. The faults in the ECU were:
P0335 Crankshaft Position (CKP) Sensor Circuit
DTC Status: Not Present
P0342 Camshaft Position (CMP) Sensor Circuit
DTC Status: Pending
My next step was to check voltage and ground connection and they were all ok. The next step was to check the crank sensor signals with a scope. See the next to images:
Here something strange happening, not sure what happened here but this could have caused the ECU to log a fault. It could be a voltage drop in the system. (Crank sensor)
This Images clearly show that the sensor did not read one tooth properly, you can see that in the square red block. The ECU will not be happy with that. I did not yet test the cam sensor, I have tested the battery just to see that the voltage is not dropping to match when the starter is cranking. Well, I noticed that the voltage drops to about 6 volts when the starter is engaged, and that is too much. I have charged the battery for a few hours and since then the ECU is not logging any faults. Hope this helps.