OBD code question

cragmor

The car is giving me P0016 and P0017 codes. I have read up on them, and it appears 17 could point to 16 being the culprit. Regular service, oil changes when the car says it is time. Vehicle has 90k miles. This is the 4 cyl engine.
So, what am I most likely looking at? One or both sensors? Basically, is there a common problem associated with this vehicle and these codes that I can begin looking at?

Mr_Shiftright

The computer codes don't necessarily point to the defective component. Often the codes are showing distress of the circuitry, or within the entire system. So, for instance, you might also get these codes with an incorrectly torqued crankshaft balancer or with timing belt issues.

thecardoc3

The codes mean that the synchronization of the crankshaft position sensor signal to the intake camshaft signal, (P0016) and the exhaust camshaft signal (P0017) has been lost.

To troubleshoot these codes correctly top shops/techs rely on a combination of routines. In a number of cases the scan tool might be all that the tech needs. The first thing to do would be to access the scan data and compare the desired camshaft positions to the actual positions in the data. Then use the bi-directional controls (if not locked out by the trouble codes) to override and actively test the system.

There are so many variations in what could be found at this point that it would take hours to type them all out, and if you don't have the ability to do the full testing (Tools and equipment issues) it really wouldn't help you anyway. But what the technician discovers during this phase of the testing with the first scan tool would determine where the focus then must go. Some examples are that maybe both camshafts show retarded angles right from the start-up. That makes a timing chain and guides quite likely and we would then use the digital oscilloscope and a pressure transducer to measure exactly what is going on in one of the cylinders. We can actually prove exactly what the camshaft timing is right through the spark plug hole on an idling engine this way. If the pressure transducer shows the cams out of time agreeing with what the computer is saying about the signals then we would be getting ready to do some disassembly.

The tech might find that the cam timing is correct at start-up but the computer loses control of it after it goes into variable valve timing. This could be a loss of oil pressure in the engine itself.
There might be enough pressure to keep the light out, but not enough to control the valve timing correctly.

The tech might find that the engine starts up in time but then moves without being commanded to by the PCM. That "could be" sticking control solenoids, or even wear in the camshaft journals in the cylinder head.

The tech might find that the engine starts up with the camshafts in time and when the PCM commands the system to change the camshaft timing, they don't move. Now the concentration is on the solenoids first, and the actuators on the cams secondly.

The really fun part here is that both cams could have different failures, and there is always potential for more than one failure with any system. You wrote that the car had been serviced regularly, specifically when the car said that it was time. Did the car get serviced with just any bulk 5W30, or was it serviced with a product that was also approved for GM spec 6094M? That is a very important question. If you find out that the camshafts don't move when they are commanded, and you pull the solenoids and find sludge restricting them, then the car wasn't serviced correctly.