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Discussion Starter #1 (Edited)
Update: Fixed! See below for the running fix log, but if you skip to the end you'll see the solution and the high level take aways.


My car threw a P0017 today at around 75K miles. I coudn't find much on the internet about how to tackle this one so I'm going to log my questions and the answers I come across as I find them. Feel free to chip in if you've dealt with this before.

Initial research:
P0017 appears to indicate a timing signal mismatch between the camshaft position sensor and the crankshaft position sensor on the exhaust side (i.e. the rear of the engine).

This can be caused by (from most to least invasive troubleshooting order):
1) A broken or disconnected wire - maybe I ran over a branch or tumbleweed and it had enough heft to break a wire (this would be more likely for the crankshaft position sensor, which is under the car)
2) A bad crankshaft or camshaft position sensor - maybe it just got tired or I bashed on f the sensors without realizing it while wrenching on something else
3) A legitimate mechanical mismtach on the timing belt - maybe the timing belt jumped a tooth (I haven't done any work here recently, but if I had then that would make this a higher probability fault source)
4) A broken tonal ring - maybe it just got tired (I haven't done any work here recently, but if I had then that would make this a higher probability fault source)

So then the high level troubleshooting steps are:
1) Inspect the wires
2) Run various voltage and resistance tests on the sensors or swap a high-probability-good replacement in and see if that fixes the issue
3) Check the timing and if it's bad, un-bad it
4) Fix it (I'm not super sure how, I've never had to mess with it so a tonal ring diagnostic and repair is probably a last resort)

Judging by the handful of other discussion on this (see below) it looks like the sensors are the most common failure point, with the timing belt being the next most common.
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Aside from the general failure trends, how might we tell the difference between a sensor failure and timing belt failure? If the sensor went bad then it likely could/would have had a slow decline into failure as heat and oxidation worked on it. This might have manifested as occasional weird engine blips or hesitations. Then again the sensor could have been banged up in which case these symptoms wouldn't have been present. A timing belt would have a pretty sudden failure mode. The months leading up to the failure probably wouldnt have had engine blips or hesitations (assuming everything else was fine). So if you had minor problems before the failure that didn't trigger a code I'd suspect the sensor. If you didn't it could still be either.

In my case, I just did a 10K mile lap around the US over a couple of weeks and I did notice some engine hesitations and blips during that time. They were momentary and inconsistent so troubleshooting them after the fact didn't really get me anywhere. Anyway, between those minor issues, the 8hr daily run times and the engine bay heat that generates, the fact that the service interval for the belt is normally 150K and we're only at 75k, and that the most common failure point is one of the senors, I think the balance of probability favors the sensors. It could still be an wiring issue - I did run over a couple of tumbleweeds on that trip.

Troubleshooting for me:
So if we're operating under a sensor/electronics first approach, here's my game plan:
1) Visually inspect the wire. Are they visibly broken or unseated?
2) Try some cheap replacement sensors. By which I mean, raid the junkyard for some replacement sensors. In the grand scheme of things, general sensor failure isn't terribly common so the odds are pretty high that any given 7th gen Ford Fiesta in the yard will have a working set of sensors. If we swap them in and the problem goes away then we've confirmed the sensor issue and can order fresh senor(s) from Amazon.
3) If that still doesn't work, it's time to break out the multimeter and check some voltages. The aptly named "How to Test Crankshaft and Camshaft Position Sensors" video by Ratchets And Wrenches will be our guide here. From the tests that he describes, we should also be able to isolate any wires that are internally broken (i.e. the wire is broken inside the cladding/sleeve without a visible break from the outside - personally I've never seen it happen).
4) After that, if everything checks out, it still could be the sensors but at this point the balance of probability has swung to a legit mechanical timing issue. The guides I;'e seen on this (youtube and Chiltin) really only cover full timing belt changes. Ideally we'd have a way of checking the timing without pulling a lot of components out of the engine bay but I'm not sure if that's possible yet.
5) Now we're in solidly low probability territory so I dont expect to get this far but for the sake of completeness: If the timing and the sensors/wiring have checked out so far it's time to start seriously digging into the tonal ring side of things.
6) If the timing is good, the sensors and wiring have so far checked out, and the tonal ring doesn't appear to be the issue then I'll just buy new sensors and drop them in.
7) If it's still throwing codes, then it's time to quit and bring it it a shop and pay the stealer (read: Dealer) to figure it out

Open Questions:
  • Is there an easy way to inspect the timing marks? I've never had to pull the cover on this make/model but it looks like we might be able to just pull the cover without getting too crazy. Does anybody have or want to write a quick guide on how to check the timing on this car
  • Anyone have a guide on how to check the tonal rings on this car?
  • What other cars use the Fiesta's 1.6L 4Cyl non-turbo? Maybe there are some more detailed guides and discussions for those cars.
Other Notes:
This is the camshaft sensor:
648


Still gotta grab a pic of the crankshaft sensor.

I work in software development so issue logs like this are more or less my bread and butter. I know it's unusual but I think the writing process helps reach a high level of understanding and maybe it'll help someone else down the line.
 

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Discussion Starter #2
I've thought more on how to troubleshoot this. There are two identical camshaft sensors on this engine. The intake side and the exhaust side. If it is a bad camshaft sensor, then I if I swap the two sensors, the code should shift to a P0016 (which after some quick googling appears to be the same issue as P0017, just for the intake side).

If the code switches then you've confirmed that it's probably a bad camshaft sensor. If the code stays the same, then it's either a bad crank sensor or legit timing issue (it could also be the lower probability issues but we're just focusing on the high side for now).

I was also thinking more on how to test the timing for this and I've more or less decided on the procedure. The engine uses a timing pin to align the crankshaft at TDC. You just stick the pin in and rotate the crank until it won't rotate anymore and that's TDC. From there, you just pull the covers and make sure the the two crankshaft alignment marks are where they should be.

I still need to find out:
How I want to pull the cover
How to confidentlly say that the crankshafts are in the right timing (the manual I see says that they should both be at the eleven oclock position but that's vague af, there's gotta be a reference mark right?)
 

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Discussion Starter #3
I swapped the sensors and still got the same code. I pulled the wheel and the lower accessory belt cover and you can in fact access all 7 of the timing belt cover screws without pulling any other components. You might not actually be able to remove it all the way but for our purposes (simply checking the timing) that's fine.

So with that in mind, our next point to check is the crankshaft sensor. It still could be a wiring issue with the camshaft sensor. I think there's an easy way to check if it's the wire though. They make multi meters that basically have clamps on them and you can place the wire between the clamps and with the engine running you'll be able to tell if it's getting a signal. Easy wire checks, boom. You could probably also use this to test the sensors but I'd need to think on it more. In any case, back to the crankshaft sensor. Wouldn't you know it, there's a 2014 Ford Fiesta in a junkyard near my house. I'll go pull that bad boy and see if that does the trick.

On second thought, if the crankshaft sensor were bad... you'd think it would throw both P0017 and P0016 since both camshafts would be right but the signal from the crankshaft would be wrong i.e. both sensors would be off from the camshafts timing.... I'm starting to think it might be a timing belt issue after all.....
 

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Discussion Starter #4
So the yard near me is closed due to quarantine. That sucks but I decided to pull the crankshaft sensor anyway and see if there was anything obviously wrong with it. There were some metal shavings on the tip so i brushed those off and put it back in and... no change.

On a lark I started generically googling for P0017 and the engine specs for this (ford, 1.6 vct 4cylinder) and I found a few other cars that use this engine. With that code though there was a trend in discussions - check the VCT solenoid. It's oil operated and I did in fact just do an oil change. I pulled the front and rear solenoids intending to swap them like I did the camshaft sensors but those don't appear to be interchangeable. While holding them both in my hands, I did notice that one was heavier than the other. The exhaust side was full of oil and the intake side was not. I don't know how this system works but I decided to shake out all the oil I could and put the solenoids back in. Lo and behold, the engine is waaay smoother now. I wouldn't call it 100% smooth but it's close.

I cleared the codes and kept checking for a pending P0017 (like had happened during all the checks before it) but I never hit one. Then I went for a quick drive and still didn't hit the code. That sounds an awful lot like I found the problem. I'm betting that either the solenoid just got stuck and the shaking unstuck it OR there's a damaged internal o-ring that's letting oil into the solenoid and that oil is preventing the solenoid from properly firing (i.e. oil is filling the cavity that the solenoid would normally activate through). A quick tour through google shows that I can get a Dorman solenoid here by Tuesday (it's Sunday as of writing this) for about half of what Autozone/AdvanceAuto wants. Um yes please. I'll install it and update you guys on Tuesday but for now this is looking pretty solved.
 

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You did an amazing job with explaining your troubleshooting! I hope that the Dorman solenoid proves to be the fix to your problem!
 

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Discussion Starter #6
Glad someone enjoyed it. I swapped the new VCT solenoid in and everything is fine. Back to 100%.

High level takeaways:
  • If it's just a P0017 or P0016 then it's probably the solenoid or the camshaft sensor. If it's both, then it's probably the crankshaft sensor. It could also be a mechanical issue with the timing (see below).
  • It's easy to diagnose which camshaft sensor is causing the problem (if it's causing a problem at all). They're interchangeable so if you swap them and the code changes then you've IDed the bad sensor. If the codes doesn't change then it's the solenoid or the timing belt.
  • The timing checks are simple but you need special tools. Advance the crankshaft until it hits the stop pin and make sure that the notches on the camshaft gears are perfectly in line and symmetrical with each other. The timing cover can be dislodged for inspection without removing all the other accessories driven by that side of the engine - you just need to jack the car up, remove the passenger side wheel and the lower plastic cover and you'll have complete if slightly awkward access to the 7 mounting bolts. If you've jumped a tooth then your idler or belt is about to fail.
  • There's not a lot of fiesta info out there since about 80% of Fiesta sales went to Europe land but the engines used in the FIesta are common in other Ford vehicles, so in addition to searching for how-to's and tutorials for this specific car, be sure to also search for the specific engine as it relates to other cars.
 
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