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Car comes in with a P1390 Cam/Crank Correlation code and note about adding coolant recently.

The Neon 2.0 doesn't have timing marks on the front cover. You guess at cylinder 1 TDC using a rod through the spark plug hole. Then look through a small hole to line up the marks on the camshaft.

So I decided to take a few minutes and scope the camshaft sensor and crankshaft sensor first.


As I pull connector 1 on the PCM. I'm greeted with what looks like coolant in the plug cavity.

enter image description here

Not good, at least the PCM didn't short.


On to the cam crank correlation.

enter image description here

It looks... OK? No signal dropouts or weird glitches.

Thanks to Fred Wilson. Cam signal is shifted to the right and cam gear was off one tooth.

I'd expect the cam signal (green) to be shifted more to the right or left if it were off.

I'm having trouble finding a known good pattern to compare to.

Can anyone provide a known good cam/crank correlation pattern?

If the pattern is good and effectively rules out timing, what are some other causes of a P1390 code?

Coolant in the PCM plug cavity could definitely be a contributing factor.


As I was doing the correlation I noticed coolant leaking from the timing cover.

So if I get confirmation I'll be tearing apart the front of the engine and will be able to confirm the correlation. As well as the source of the leak, most likely a water pump.


Update

Tore apart the front of the engine today. Forgot to get a picture of the cam gear, the locator pin was fine and the cam gear was off one tooth.

To bad the front cover is hidden behind the front mount/power steering/tensioner plate.

enter image description here enter image description here enter image description here

Oh well.

The car now has a new water pump, tensioner belt and cam gear locator pin.

  • 1
    Great question @ben. I wish I could be helpful but my knowledge is lacking in this area. Looking for to seeing great answer hopefully. +1 – DucatiKiller Apr 14 '16 at 1:52
  • As always, a great question @Ben +1 – cdunn Apr 14 '16 at 12:42
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I checked a known good waveform (cannot copy here, copyrighted). Yours is shifted just a bit to the right. Around your frame 95 that cam sensor vertical line should exactly bisect the horizontal line on the crank signal.

Most common failure for a small shift is bending of the locator roll pin on the cam pulley.

  • Is inserting a copyrighted image of a waveform here for educational purposes a problem, considering that the author was mentioned? – I have no idea what I'm doing Apr 14 '16 at 11:34
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    @IhavenoideawhatI'mdoing I would think it would fall under fair use as long as credit was given. But it may not be worth taking a chance. – Ben Apr 14 '16 at 12:18
  • @IhavenoideawhatI'mdoing The waveform in question is owned by a site in the small and provincial world of professional automotive technical sites. A place a cannot afford to become blacklisted. – Fred Wilson Apr 14 '16 at 14:27
  • Is it a technical service platform, or a community of some sorts? A link then, perhaps? – I have no idea what I'm doing Apr 14 '16 at 15:40
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    @IhavenoideawhatI'mdoing It is a community called iATN. It requires industry credentials to sign up and it is has a monthly fee to access much of the data. www.iatn.net – Fred Wilson Apr 14 '16 at 18:28

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