P0302, P0316, and P0171 codes with "new" 02 V6

Dwright

Member
Jun 5, 2020
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Wayne, pa
Hi Everyone,

My son turns 16 in two months and we picked up a 2002 V6 Mustang and we have been working on it. We started out with codes P1336 and P0401. Before this we replaced plugs, wires, and air and fuel filters. We started working on P1336 first. We replaced the crank sensor (cause it was cheap) and didn't notice a change. The car doesn't idle that well (not terrible) but I do notice some sputtering while driving. Someone told me that the rough idle could be causing the codes. I troubleshot the EGR system and confirmed a bad DPFE sensor. Replace that and P0401 went away. Then decided to replace the cam sensor. Since the sync wasn't that much difference I decided to replace that too. I installed this according to the instructions in the forums. Not 100% confident in this because at TDC the old one did not have the stator in the window (see first pic). When I installed, the stator is lined up in the window but I couldn't quite get the arrow on the alignment tool exactly where I wanted it (see pics).

So, we fired it up and all codes gone. But then while driving we got the flashing SES light and P0302, P0316, and P0171 codes. Cleared and they come back. When installing the sync I did crack the EGR pipe that goes to the manifold. Could this cause the codes? My first thought was my son didn't tighten the plug but it was tight.

Any help appreciated.

Daniel
 

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MustangIIMatt

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Mod Dude
Mar 7, 2002
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A cracked EGR pipe can cause the P0171, as that's a system lean code for bank 1, and any exhaust leak forward of the O2 sensor can cause that.

As far as the P0302 and P0316, they're related. The P0316 means there's a misfire at startup, and P0302 is telling you it's on cylinder number 2.

Misfires are easy to diagnose when isolated to one cylinder.

First things first, verify the source of the misfire.

Swap the spark plug from cylinder 2 with one from another cylinder and the coil from 2 with the coil from another (different) cylinder (example would be to use 1for the plug and 3 for the coil). Start the car and run the codes. If the misfire moved from 2 to one of the other cylinders, the part you moved to that cylinder is bad. If the misfire doesn't move, keep reading.

Make sure you are getting fuel to cylinder 2. A set of noid lights (parts stores have them either in their loaner tools or for sale) will tell you if the injector is getting signal to squirt fuel or not, if it is, swap the injector with one from another cylinder (do while engine is cool and after relieving fuel pressure) and starting the engine and running codes to see if the misfire moves. If it does, you need an injector. If you weren't getting signal to the injector, the problem is in the wiring harness or ECM. If the wiring and injector check out, keep reading.

If you have spark and fuel, the problem is mechanical. Buy/rent/borrow a compression tester and do a compression test. There are videos on Youtube on how to do one, and most testers come with basic instructions. If cylinder 2 is in spec and within tolerances in relation to the other 5 cylinders, the problem is in the valvetrain. If it's very low or zero, the problem is going to require some engine teardown to find. Either way, at that point, you're pulling a valvecover.
 

Dwright

Member
Jun 5, 2020
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Wayne, pa
Thanks for the help. I'll get some exhaust tape to seal the crack while I wait to get a new EGR tube. Is it possible that I am one tooth off on the cam sync? I read something about if its incorrect it could cause lean condition.

Daniel
 

MustangIIMatt

I need something stupid to play with
Mod Dude
Mar 7, 2002
8,113
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Thanks for the help. I'll get some exhaust tape to seal the crack while I wait to get a new EGR tube. Is it possible that I am one tooth off on the cam sync? I read something about if its incorrect it could cause lean condition.

Daniel
I would think it'd cause a P0016 (camshaft position correlation) code, but I'm not incredibly familiar with the 3.8 overall, I just happen to work on cars for a living. I suppose it's possible if the injectors run off of the cam position sensor reading.
 

Dwright

Member
Jun 5, 2020
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Wayne, pa
patching the EGR tube elimintated the 0710 code. Still have the others. So far I switched the plugs between 1 and 2 and problem is the same.
 

MustangIIMatt

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Mod Dude
Mar 7, 2002
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patching the EGR tube elimintated the 0710 code. Still have the others. So far I switched the plugs between 1 and 2 and problem is the same.
Try swapping a plug wire (both ends), if that doesn't make the code move... there's a way to test the ignition coil if I can find the specs needed (since yours uses a single coil pack).

https://easyautodiagnostics.com/ford/3.0L-3.8L/how-to-test-the-coil-pack-1 Hell, I went looking for the resistance specs to tell you how to do a basic test on the coil, and this guy has a well-written, with pictures, how-to on how to test it multiple ways.
 
Last edited:

Dwright

Member
Jun 5, 2020
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Wayne, pa
Plug swap no change. I’ll test the coil.

many idea whether there are timing marks on this V6? Looked all around and can’t find them even though the manual shows them
Daniel
 

Dwright

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Jun 5, 2020
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Wayne, pa
Ok I’ve confirmed that the sync is installed correctly.
I was looking for resistance too. Some conflicting info on this. Seems 1.0 is what some guys have found. But the article shows .45 - 2 ohms. I get 1.7, 1.7, and 1.2.
 

MustangIIMatt

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Mod Dude
Mar 7, 2002
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Ok I’ve confirmed that the sync is installed correctly.
I was looking for resistance too. Some conflicting info on this. Seems 1.0 is what some guys have found. But the article shows .45 - 2 ohms. I get 1.7, 1.7, and 1.2.
If the resistance is in spec, I'd use a spark tester to verify it's firing. They're usually pretty cheap at the parts stores.
 

Dwright

Member
Jun 5, 2020
12
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47
Wayne, pa
Didn't even get to fully test the resistance. The readings above were with the wires attached so that didn't help.

After pulling the cam sync to be 100% positive I didn't do something wrong I confirmed it was correct. It was a bit of a puzzle because I haven't had any misfiring codes before. So, I thought I messed up even though that install is pretty basic. The car has been running rough since we got it and now I know why. I had replaced plugs and wires but didn't test the coil. I order a tester and in 3 minutes the problem was obvious. No spark on #2. Replace the coil (or watched my son do it) and it runs great! Lesson learned here was to trust your work. i was confident going into it and had resources here and others online. But secondly, I skipped over the coil test because I had never gotten a misfire code before. I think the cam code P1336 was taking priority over the P0302. The other issue was that the original cam sync was clearly not installed correctly - thus throwing P1336. I think the previous owner tried to mess with it and messed it up.

Anyway, glad it's all better now! Thanks for the help.

Daniel