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Old 08-16-2010, 02:56 PM   #1
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Default Crank pos sensor not reading new jdm engine??

hey guys, I recently needed to exchange the engine in my 96miata and with some delay from the "friend recommended" (crap) mechanic, i finally got it back with a new (used)low mile japan engine.

Runs strong and great but the engine light is on and after a scan I found out it's the "crank shaft position sensor"... I've gotten it replaced but the bracket that it sits on is about an inch from the crank wheel and not surprisingly the "error" isn't going away. i've checked with several mechanics but nobody quite knows and I keep being told that I should ask dealer. Mazda dealer is telling me $300 for their diagnostic but I don't have money to throw away to learn what I know so... tried to simply move it closer but it's not aligning right to get a reading so that didn't help and it caused the bracket to not be in place right... so I shifted it back to the inch away situation...


Has anybody had this kind of issue or got an idea as to what I need to look for when i close the distance (don't see any mark to align it with)??

starting to think maybe the japanese engines have some different specs or brackets or somehting??

need to get this thing off so I can pass smog before end of month http://www.boostedmiata.com/avatar/f...if:(:facepalm:
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Old 08-16-2010, 03:02 PM   #2
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the 96 has a CAS...
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Old 08-16-2010, 03:24 PM   #3
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hmm sorry, what is CAS?
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Old 08-16-2010, 03:24 PM   #4
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Indeed- it would be helpful to know exactly which P-code the ECU is throwing, as the '96 and '97 cars actually have two crank position sensors.

The one which is actually mounted next to the crank pulley is not a primary trigger. It was added to satisfy the requirement for more stringent misfire detection with OBD-II, and its sole job is to throw an error code. You can remove it completely and the engine will still run just fine.

Then, at the back of the head on the exhaust side, there is a second sensor, a large can which we refer to as the CAS (cam/crank angle sensor). This device outputs two signals, one for absolute cam position, the other for crank TDC/BDC. This sensor is the primary operating sensor for all '90-'97 Miatas.


From your description, I'm guessing that the error is for the one down by the crank, and of course you're not going to pass a CA smog inspection unless you get that rectified.

So, give us a specific P-code, and a clear picture would also be nice.
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Old 08-16-2010, 03:39 PM   #5
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oh wow that makes so much sense... I actually took sensor out now to get a picture of the bracket and indeed the car drove me home just fine...

the PO code I'm getting is "PO335"

the org sensor that we pulled out had some exposed wire from having rubbed up on something so I didn't question it being bad but according to manual it's supposed to
be .020-.059 inches from pulley and it's no where near that

is there a magnetic trigger or something to satisfy the sensor in addition to the distance that might not exist in my new pulley?
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Old 08-16-2010, 03:41 PM   #6
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exactly.
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Old 08-16-2010, 03:47 PM   #7
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Move to a state that doesnt require gaymissions testing
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Old 08-16-2010, 03:48 PM   #8
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Yeah, pretty sure P0335 is for the one down by the crank pulley.

Honestly, a picture would be really helpful.

The sensor is supposed to be pointing at a toothed plate which sits behind the pulley, not at the pulley itself. The plate is fairly thin, and has four unevenly spaced teeth. With your new engine being a JDM pull, I'm wondering if perhaps you're just missing the wheel altogether??
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Old 08-17-2010, 11:34 AM   #9
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If there's a crank sensor, could the "new" crank pulley, not have the trigger wheel as part of it?

Might want to look if you still have something for the sensor to be triggered with. Some UK models didn't have ODB-II in 96/97, so it's possible your jdm new motor doesn't either....

Dave,
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Old 08-17-2010, 08:48 PM   #10
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yeah steel that's what I fear :(

Joe I'm gonna get a clean picture to post up -thank you so much for your info - you clearly know your thing -thanks!

anybody have an idea if I could simply swap out the crank pulley with a us version that has the trigger wheel if this is the case??

I am not sure but i've had some restles idle in my car that i've thought was caused by this ...that's why I don't just want to figure out a way to "pass smog" but to actually fix the issue... arg
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