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Old 06-02-2019, 08:32 PM   #1
Harlard
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Default MS3X+DSM CAS - No cam signal

Hi all,

Been following Nick's guide and the MS3X hardware manual for this: there is zero cam signal. CAS produces a good cam signal when the channel is switched to the crank input on the mainboard, so a sensor and harness issue has been ruled out.

I see a non-pulled up cam signal output at the sensor connector of .3v, which is congruent with a non-pulled-up signal.

I also bypassed the internall pullup in the expansion board to tps vref, still nothing.

Is there a way for me to fault trace this in the expansion card? Can it be a problem with the connection between expansion card to daughtercard? Daughtercard to main board?

Input would be greatly appreciated and would love to fix this before plonking down the cash for a new box.
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Old 06-02-2019, 09:33 PM   #2
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When you say you bypassed the internal pullup, what do you mean? Pulled the jumper, or added your own pullup resistor?

If you measure the voltage (to ground) of the cam/crank pins on the CAS, and spin it by hand, do both signals swing between ~0 and ~5volts? If you see the signals swing, the next area to check is that the POTs are adjusted correctly. A composite tooth log should show activity on both cam/crank.
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Old 06-02-2019, 09:42 PM   #3
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1. Yes I pulled the jumper and added my own 1k resistor between tps vref and 32-cam in.

2. Cam signal goes between 0 and .3v. Crank signal is 0-5v. If I pin the cam channel to the crank input, it shows 0-5v as it should. In that vein I have been running composite logs to confirm, and they agree with what I see using the multimeter when spinning it by hand.
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Old 06-02-2019, 09:59 PM   #4
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Do you see any voltage change on 32-cam in? A tiny change would be more encouraging than none at all.

Sounds like your MS3X Expansion Card has problems. You could unplug the 37-pin expansion connector and see if you can see pin 32 swing between ground and ~+5v as you jumper/un-jumper the internal pullup (JP7).

I don't know if you could setup crank/cam using the MS2 circuits, and if the MS3X software could use Cam from the MS2 circuit.

Edit: did you check that tps vref actually has ~5v on it?

Last edited by bobxyz; 06-02-2019 at 10:07 PM..
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Old 06-03-2019, 12:36 PM   #5
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I mean the voltage without any pullups is still noticeable. As expected it's a very weak signal.

Coming to think of it, I installed the pullup close to the ECU plug in the harness. There should be a signal whether the ECU is registering a signal or not, which actually does not rule out the harness being suspect, but suspect #1 in fact. I will be doing some more testing here today or tomorrow.
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Old 06-03-2019, 12:55 PM   #6
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I don't like using the vr circuits for hall sensor inputs, I ended up bypassing the onboard **** after I had some odd issues with the 940
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Old 06-03-2019, 01:21 PM   #7
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I could always sell this thing and get a Maxxecu for not a whole lot more...
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Old 06-03-2019, 01:28 PM   #8
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something like this http://www.jbperf.com/dual_VR/v2_1.html
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Old 06-03-2019, 01:29 PM   #9
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but I think sparkfun has something similar for less? it's basically a reference board for the max chip.
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Old 06-03-2019, 01:38 PM   #10
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Oh I'm gonna need one of those for vss2 eventually.
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Old 06-03-2019, 01:44 PM   #11
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get a pair then. one for the wheel speed sensors, one for the cas.
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Old 06-14-2019, 12:41 PM   #12
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Figured it out. I'm stupid and mixed up the IAC and cam signal wires (both slightly different shades of green). It works now.
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Old 06-20-2019, 01:49 PM   #13
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Quote:
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Figured it out. I'm stupid and mixed up the IAC and cam signal wires (both slightly different shades of green). It works now.
Darn, I was just about to tell you to get LH2.4 on that bitch.
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Old 06-20-2019, 09:35 PM   #14
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I use all black wires so I don't have trouble seeing the different shades of green!
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Old 06-20-2019, 09:39 PM   #15
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I use all black wires so I don't have trouble seeing the different shades of green!
Lol.
I worked on a racecar where the entire harness was white wire with number tags on the ends of the wires. Not too bad, but tracing kind of sucked.

I also worked on a custom RV that was almost all yellow wires, but with no numbers. Infinite suck.
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