1. Carry out a fault report and obtain the correct codes.
2 fault(s) Present
Audi – P0017 Crankshaft Position Camshaft Position Correlation Bank 1 Sensor B
Audi – P0016 Crankshaft Position Camshaft Position Correlation Bank 1 Sensor A
2. What does the code mean?
This fault code means that the camshaft position sensors on both camshafts are detecting that the cam to crank timing is out of spec. i.e. the measured number of teeth between the crankshaft trigger and the camshaft trigger do not match.
Due to both camshafts flagging cam to crank correlation codes we can safely assume that the cam to cam timing is within spec, and the issue is the crank to cam timing.
3. So how do we test it?
The first knee jerk reaction to an Audi with a P0016 might be to pull all the timing covers off and the engine mount and re-time the engine and check the physical timing, AKA get stuck right in and get involved.
However there is another way that doesn’t involve the removal of any parts whatsoever and within 15 minutes we can get a clear direction as to whether we need to start pulling timing covers.
Thanks to the availability of modern automotive oscilloscope tools such as the Picoscope, we can very quickly determine the fault without removing any parts.
In the case of this vehicle I measured the camshaft signal for both camshafts, and the crankshaft signal against each other with and took approximately 15 minutes to test.
Looking at the trace below labelled Trace 1, we can see that the green trace shows the crankshaft signal, the blue trace shows the intake camshaft signal and the red shows the exhaust camshaft signal.
In our case, I was fortunate to have another vehicle in the shop with the exact same engine so I could easily scope the same data points on the other vehicle and have a known good to compare too.
Alternatively the Picoscope features a waveform library that allows you to look up a library of previous Picoscope users waveform to compare with and is a priceless tool. We now have all the necessary data to make an informed decision over after some analysis.
Now, the squiggly lines are often the first thing to scare people away and prevent this kind of diagnostic work being done confidently, but If we take 5 minutes to look and see what is going on, we can begin to build a picture of what the ECU is seeing, and why the Audi P0016 DTC was stored.
First of all we need to know what we need to know, weirdly enough. So we need to know the number of teeth between each camshaft, and then the number of teeth between the camshaft and the crankshaft and then compare this to the known good waveform, any discrepancies will tell us who the culprit is and warrants us going in further.
Trace 1 shows that the amount of teeth between the missing crankshaft tooth, and the next red trigger is 3.5 teeth, and the number of teeth between the end of the red trigger and the blue trigger is half a tooth.
Now looking at the known good waveform of Trace 2, we can gather that the number of teeth between the cranks missing tooth on the green trace and the exhaust cams red trigger is 6 teeth, and the number of teeth between the end of the red trigger and the blue trigger is also approximately half a tooth.
5. And breathe
So lets take a step back from the scary lines. What do we see? Well as we just discussed the timing between the camshafts has been proven good, as both traces match at 0.5 teeth apart. Whereas the crank to exhaust cam timing of Trace 1 is 3 teeth advanced of Trace 2
This proves that the Crank to Cam timing is out and by exact;y how much, without touching a single spanner. Now as a footnote it is important to state that 3 teeth variation is not 3 teeth on the timing chain, but 3 teeth on the crank trigger.
6. So, What now?
Now we have all the data to go back to the customer and say “This is whats wrong”, all without getting dirty and taking around 30 mins start to finish. The elephant in the room however is how does the cam/crank timing get to the point of triggering a P0016 and P0017?
Well the ECU has a threshold for how many teeth apart the cam and crankshaft timing are allowed to be, and if its crossed as we see here the DTC’s are triggered.
The threshold can be triggered for many reasons, 2 of the main reasons are an incorrectly installed timing chain or an excessively worn timing chain that is now effectively 3 teeth longer than it should be.
Other factors that should be considered are the influence that camshaft phase adjusters have, a camshaft phase adjuster. When they are stuck in a position whereby the cam timing is the advanced position it will have the same affect. One way to get around this is to unplug the phase adjusters on both the known good engine and the one in question.
The cause of why the cam timing is out is not what you need to tell the customer at this stage. But what you will have is evidence for the customer to spend his money on the Audi P0016 diagnosis while you spend a few hours further investigating the vehicle.