2015 CX-5 Long crank issue

I am new on this forum, hoping to get some help. I have a 2015 cx5 having issue with long crank. The issue is intermittent. Once the car starts, there is no issue like stalling or misfire, fuel economy.
I’ve recently changed battery (energizer group 35, 640 CCA). Alternator also charges fine (tested with multimeter).
Sometimes, with long crank results check engine p0335 code (crankshaft positioning sensor code). I have also changed that sensor but no luck.
I am hoping to get some suggestion from this forum.
Thank you
 
With the engine idling, try wiggling the wires running from the crank sensor to the PCM - both the individual sensor harness and the big bundle running from the small harness to the PCM. If anything changes with the way the engines idles, then you've on your way to resolving the issue.

If nothing happens with that test, then you should test the crank sensor circuits, first with a multimeter. If nothing abnormal shows up with that, then the signal should be scoped, in order to see if there's anything unusual with the waveform. It's also never a bad idea to test the charging system for excessive ripple.
 
With the engine idling, try wiggling the wires running from the crank sensor to the PCM - both the individual sensor harness and the big bundle running from the small harness to the PCM. If anything changes with the way the engines idles, then you've on your way to resolving the issue.

If nothing happens with that test, then you should test the crank sensor circuits, first with a multimeter. If nothing abnormal shows up with that, then the signal should be scoped, in order to see if there's anything unusual with the waveform. It's also never a bad idea to test the charging system for excessive ripple.
Thank you for sharing your suggestion. I am comfortable doing the 1st part where I need to wiggle the wire. But I am not sure how to test sensor circuit. Any YouTube video or instruction would be appreciated. Thank you.
 
Thank you for sharing your suggestion. I am comfortable doing the 1st part where I need to wiggle the wire. But I am not sure how to test sensor circuit. Any YouTube video or instruction would be appreciated. Thank you.
You can do the simple multimeter testing by first removing the crank sensor connector, set your meter to DCV, connect one probe of the meter to connector pin A and the other probe to the negative battery ground post. Then have a helper crank the engine for a few seconds and watch the meter display to see how much (if any) deviation there is from a constant 5V reading.

Next, connect one probe of the meter to connector pin B and the other probe to the positive battery ground post. Then once again crank the engine for a few seconds and watch the meter display to see how much (if any) deviation there is from a constant B+ reading.

You can test the signal wire with a meter by backprobing, but there's usually not very much that can be determined by doing that, unless the signals are way off. The only meaningful way to test the signal is by using a scope, which for most DIYers normally means taking it to a shop. Someone who knows how to use a scope well can discover quite a bit of information by observing and evaluating sensor waveforms.
 
Thank you edmaz. I will check the sensor using a multimeter the way you explained and share the results. Besides that, should I also check fuel pumps even though there is no issues driving the car when it starts. Some forums also suggested low pressure fuel pump caused long crank on other Mazda models. Any thoughts.
Thank you
 
Thank you edmaz. I will check the sensor using a multimeter the way you explained and share the results. Besides that, should I also check fuel pumps even though there is no issues driving the car when it starts. Some forums also suggested low pressure fuel pump caused long crank on other Mazda models. Any thoughts.
Thank you
Although the low pressure fuel pump can be tested, the HPFP cannot. However, an OBD live data reader will provide fuel rail pressure while cranking, which can be checked against the specified value, and that will tell you if both of the fuel pumps are ok. If this were my problem, I'd be trying to get an answer to why that code is being set, before spending time on anything beyond checking the fuel rail pressure.
 
Hi Edmaz
Update: LPFP is good as per mechanic. He also checked the wire of the crankshaft position sensor no issue there. I was told to replace the crankshaft position sensor with the one doesn’t need programming or relearning. Ordered Delphi sensor from rockauto and will install soon and share update.
However, i’m encountering a new issue while using the scanner mechanic noticed the RPM was low (500-550) during idle so he reset the throttle body and tried the relearn process But not sure it was done properly because after the reset/relearn throttle body response is very poor. Specially when I floored the gas fed the p.m. does not go over 4000. Do I need to take it to Mazda dealer ?
Any suggestion?
Thank you.
 
I hope you don't take this the wrong way, because it's not intended to be rude or obnoxious. When I read your OP, it sounded to me that you were going to be DIYing everything that we discussed previously. But after reading your latest post, it's clear now that you're having a shop do most of it. I don't give advice with the intention of having it passed along to a shop, because history has proven that to be a waste of everyone's time. The combination of the information not being communicated correctly, coupled with most shop pros not being interested in listening to 'internet experts', makes this totally nonproductive.

I'm not in any way being critical that you're taking your vehicle to a shop - the overwhelming percentage of owners do so. I certainly wish you well with your vehicle's issues, and hope you find someone who can diagnose the problems and get them resolved quickly!
 
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