DIYPNP MS2Extra - Stalling due to Sync Loss Reason 39, CAS signal - Miata Turbo Forum - Boost cars, acquire cats.

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Old 05-29-2016, 10:00 AM   #1
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Default DIYPNP MS2Extra - Stalling due to Sync Loss Reason 39, CAS signal

06/01/2017
Spark plugs. Yes. NGK R5671A-8 resistor-less plugs have been the culprit all along...at least it seems. How embarrassing to have done all this troubleshooting and also having known that resistor-less wreaks havoc on electrical systems...but never thought to check them.

Putting some bkr7e-11 plugs in tomorrow and fixing a vacuum leak, then putting this goddamn car back on the road to find out if this case can be closed.

05/18/2017
It's back. Injector driver for INJ3 and INJ4 shorted to ground, and flooded those cylinders. Check datalog with car running, and the Lost Sync Reason 39 is still present...

Here's the datalog - this was taken with alternator disconnected.
http://https://www.miataturbo.net/at...1&d=1495160502

I'm at wits end. Currently going through all the circuits associated with the 1B 12v ECU output White/Red wiring which ties the Camshaft position sensor and Fuel injector circuits, among other sensors.

What I've just noticed now, is the voltage certainly spikes a bit as the issue is occurring, but SecL is not reset which indicates the processor stays running. I'm going to re-re-recheck all my grounds yet again to make sure there's absolutely nothing wrong there.

Also, I'm assuming the VND5N07 Mosfet Injector driver shorted drain-source due to overvoltage? Any ideas here?





Thought resolved - 06/01/2016
Built completely new COP conversion wiring harness, and wired in two new 4700uF 30v caps (from RadioShack) in parallel across 12v and GND harness-side. Drove the car all day without issue and composite logger looks perfect. It appears that even though I was previously able to run without the 10,000uF cap, I don't have a choice now. Happy to be back on the road...and just in time for the good weather.







Original issue:
Here's the deal.

I started this related thread back in January: https://www.miataturbo.net/megasquir...ge-drop-87370/
In summary of that issue, it appeared that one of the two hall effect sensors inside the CAS decided to short to 12v causing a no-start condition. That was resolved by simply replacing the CAS.

A few months ago, I took the car for a spin and noticed that it was missing under boost after topping off at a gas station. Presumed to be a bad tank, the next move was to top off with very expensive 100 Octane and turn down my boost, which alleviated the issues. However, not before causing a leak in my head-gasket which subsequently let loose a few days later.

Fast forward to this month. Head is rebuilt, bolted up, and I'm starting the engine without the plugs in to build oil pressure. During this, geysers of gas spray all over my garage through the spark plug holes. During diagnostics, I discover that Injector bank 1 FET is shorted to ground pulling the related injectors to 100% duty cycle...good thing I didn't hydro-lock. Interesting that I've smoked two sensors that are related to the same WHT/RED 12V power source...although grounds are good.

FET fixed, and finally start engine. The thing is purring like a kitten, and then falls on it's ***. Start again, runs great...takes a couple of RPM hits and then stalls again. Diagnostics begin.

Here's what I found:
  • Datalogs show "Lost Sync Reason 39" which is related to the 4G63 CAS, and this causes timing to be completely lost AKA RPMs drop to 0. During timing loss event, MS thinks the engine was re-started and thus ASE ensues which causes engine to run unnecessarily rich - if during ASE another timing loss occurs, the engine will be too weak to recover and stalls.
  • Acquire by oscilloscope, 12v signal feeding MegaSquirt appears to have noise which is causing disruption of the 12V (Opto -) signal feeding MegaSquirt. This is evident by probing the 12v power source (2B) and grounding pins inside the MS chassis, and comparing to 12v directly connecting to battery.
  • Scope shows malformed square wave during engine run just prior to timing loss, which appears to be smoking gun. This is likely related to the aforementioned dirty 12v signal.
  • Issue is intermittent, but is most prevalent during idle and low speeds.

Some Trouble-shooting attempted:
  • Re-did all grounds....three times. Under brake booster, behind intake manifold, at throttle body, at battery, and PPF.
  • Replaced CAS with replacement unit and a known good OEM unit
  • Checked all CAS and associated wiring
  • Bypassed Main Relay and Fuel Injector related
  • Unplugged alternator in case of bad regulator
  • Charged car battery and kept on during run to prevent voltage drops
  • Unplugged EVERYTHING not essential to running (all fuses, relays, etc.)
  • Fed MS direct from JimStim to eliminate MS circuitry as culprit. No timing loss.

At this point I'm debating on re-running the CAS wiring direct to the ECU as a test. I'm at wits end and just want to drive this damn car again, because up until January it was daily-driver reliable.

Any ideas are greatly appreciated...so, thanks in advance.

Malformed square way before timing loss event

Overview of timing loss - note the waves spacing out starting from 25% in due to loss of timing and engine recovery

Example of 12v spikes looking at voltage supplied to ECU

More examples of voltage spikes

Composite logger showing tooth dropping out due to malformed CAS signal

Datalog showing timing loss event (sync loss reason 39)
Attached Thumbnails
DIYPNP MS2Extra - Stalling due to Sync Loss Reason 39, CAS signal-80-20160528_210237_3e29dd758396cc2dc3174b0c1b1bd06a8f76df83.jpg   DIYPNP MS2Extra - Stalling due to Sync Loss Reason 39, CAS signal-80-20160528_210306_1cf54f451cdc23953bcca55573cfde70b6deb0fa.jpg   DIYPNP MS2Extra - Stalling due to Sync Loss Reason 39, CAS signal-80-20160528_210444_506443c44d8c6db31e37ed1e0893af9d59667c1c.jpg   DIYPNP MS2Extra - Stalling due to Sync Loss Reason 39, CAS signal-80-20160528_211412_64c5f9581dc1faa436810f893962b405599dc43a.jpg   DIYPNP MS2Extra - Stalling due to Sync Loss Reason 39, CAS signal-80-composite_logger_lost_sync_49d1ae293ed8cc69ec093e315fc5e23295237d82.png  

DIYPNP MS2Extra - Stalling due to Sync Loss Reason 39, CAS signal-80-msl_lost_sync_794189a3a2e9079f010ddbc1abfbd2c5bc120ad5.png   DIYPNP MS2Extra - Stalling due to Sync Loss Reason 39, CAS signal-80-20160601_113552_89f5e765a7f422405bbecce2a791229c4a11cce6.jpg  
Attached Files
File Type: msl 2017-05-18_21_modified.msl (35.8 KB, 16 views)

Last edited by JustinOMGWTF; 06-01-2017 at 11:33 PM. Reason: Brought back from the dead
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Old 05-29-2016, 08:44 PM   #2
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Tried wiring CAS 12V direct to battery, and ran wire direct from OPTO- to MS. No dice.

Actual composite logger snapshot and log attached.

Attached Thumbnails
DIYPNP MS2Extra - Stalling due to Sync Loss Reason 39, CAS signal-80-composite_e6de9285a3aadebf6311aca23ac79d4fbdb6c02a.png  
Attached Files
File Type: csv 2016-05-29_19.39.03.csv (79.5 KB, 22 views)
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Old 05-30-2016, 04:26 AM   #3
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Sync loss 39's in my car were bad coils and a bad CAS. Both were causing Sync 39's and was a bitch to figure out.
No idea if your using COPS or not.
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Old 05-30-2016, 06:48 AM   #4
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Quote:
Originally Posted by adryargument View Post
Sync loss 39's in my car were bad coils and a bad CAS. Both were causing Sync 39's and was a bitch to figure out.
No idea if your using COPS or not.
Third CAS, so it's not that, and just got brand new COPs.

One thing worth noting is I removed the 10,000 uF cap due to leaking.

Maybe I'll try swapping the stock coils as a test.
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Old 05-30-2016, 09:58 AM   #5
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Are the pull-ups wired to 12V or 5V? Try opposite of whatever you have and see if it makes a difference. I have MS3 and an 01 engine but I would get sync losses with my pull ups wired to 12V and they completely disappeared when I put them to 5v.

I would have guessed this to be a ground problem but you said you covered that. And on the voltage spikes, while they may be present I don't know that it would affect the ecu. It should have a voltage regulator that can handle that or the ecu would be toast in no time.

Edit: and you can try different resistors for the pull ups instead of just the 1K ohm recommended. I know it's a proven installation but not every car is going to be identical for one reason or another.
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Old 05-30-2016, 11:58 AM   #6
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Quote:
Originally Posted by hector View Post
Are the pull-ups wired to 12V or 5V? Try opposite of whatever you have and see if it makes a difference. I have MS3 and an 01 engine but I would get sync losses with my pull ups wired to 12V and they completely disappeared when I put them to 5v.

I would have guessed this to be a ground problem but you said you covered that. And on the voltage spikes, while they may be present I don't know that it would affect the ecu. It should have a voltage regulator that can handle that or the ecu would be toast in no time.

Edit: and you can try different resistors for the pull ups instead of just the 1K ohm recommended. I know it's a proven installation but not every car is going to be identical for one reason or another.
That's a great idea. I certainly noticed the issues with the 12v waveform but have not verified if 5v is encountering the same issues...I'd imagine not since I've only received sync loss reason 39 which indicates Opto - (12v signal). The voltage drop is approx .5v for the 12v waveform...will verify 5v as well.

The odd thing is that the car ran rock solid for years. Something changed, but I'll try the 5v pull up regardless and see how it fares. Will also measure pull up resistance and make sure nothing happened to that resistor...visual I didn't notice any browning, etc. Thanks for the recommendations!
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Old 06-01-2016, 10:15 PM   #7
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Resolved. Explanation in first post.
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Old 05-18-2017, 11:16 PM   #8
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Back to the trouble-shooting drawing board.
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Old 07-22-2017, 01:41 PM   #9
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Quote:
Originally Posted by JustinOMGWTF View Post
Back to the trouble-shooting drawing board.
Any luck

I have a similar problem but only became more notorius when i turn on boost control.
check the video from second 50 to 60 the compose log is like yours...

https://www.miataturbo.net/megasquir...-signal-92626/
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Old 07-22-2017, 02:52 PM   #10
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what model year?

pics of how you built the MS please.
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Old 07-23-2017, 12:28 PM   #11
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Quote:
Originally Posted by Braineack View Post
what model year?

pics of how you built the MS please.
hi there

My MS is a DIYPNP 1.5 and my miata is 1.8 1996
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Old 07-23-2017, 01:42 PM   #12
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hi there

My MS is a DIYPNP 1.5 and my miata is 1.8 1996
I don't I don't see the pictures
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Old 07-23-2017, 01:47 PM   #13
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Old 07-23-2017, 01:50 PM   #14
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Sorry for the size...

I notice that there is missing R14 2.2K 1/4W resistor
on the board it connects to vref

Edit
ok r14 is because AC

Last edited by vitorjorge; 07-23-2017 at 03:04 PM.
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