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Thread: Extended Crank, Hard Start, No Tach

  1. #1
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    Extended Crank, Hard Start, No Tach

    Hey guys, been trying to figure out an extended crank, backfire, no tach issue for a while now and could use some help.
    Some breakdown
    Ls7 engine wet sump ls3 front cover, cammed (ls7s), longtubes
    e38 ecm (12633238)
    PSI Harness (har-1035)
    DBW Pedal (10379038)
    Throttle Body (217-3153
    MAF (213-4222)
    CMP (12591720)
    CKPS (12585546)
    Speedhut freedom canbus gauges
    Sooooo, I get the engine in and try to start the vehicle and it has an extended crank and is backfiring, but does eventually start up. Go get the car tuned and dyno'd and it does great (520whp) but the tuner is having problems getting rpm signal and cannot perform crank relearn. I figured i would look into it, the car is setting codes p0315 crank relearn and a p0336 ckps performance. Try to do a relearn with the tech2 and can not get passed the "start engine and let idle" screen. Attempt to do a relearn with the vcm scanner and it seems like i did (hit fuel cutoff). Shut the car off and restart and the p0315 is still present can not be cleared. Me and some of my buddies do a bunch of testing, swap ckps, swap cmp with no luck. Hook up a tech2 and monitor ignition data and find that the ckps active counter is only incrementing when the vehicle is cranking. Once the vehicle has started it stops incrementing. Everything seems to be working sensor wise so we try a new e38 pcm, that did not work either. It seems like my tach problem is directly related to the ckps active counter because when the car is cranking i can see my tach bounce around 250rpm, but then drops to 0 once the car is running. This also seems like it may be causing tech2 fail crank relearn as well. Has anybody ever experienced this?
    Tune and some videos attached. Thanks!!
    Attached Files Attached Files

  2. #2
    Tuning Addict 5FDP's Avatar
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    Do you want the MAF settings under the engine diag tab to be like it's failed?

    You are running the MAF but telling it not to use it and the DTC's aren't set right for how it is now. Set the high/low hz fail settings back to stock if you were wanting to use the MAF sensor as like factory. Otherwise set the MAF dtc's to MIL on first error if this is a speed density only tune.

    That may help with the extended crank when trying to start it because it can't fail the MAF right away.
    2016 Silverado CCSB 5.3/6L80e, not as slow but still heavy.

    If you don't post your tune and logs when you have questions you aren't helping yourself.

  3. #3
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    Thank you. I am actually not the one who tuned the vehicle. Had it done at a shop, ended up borrowing hptuners to write the shops tune onto a new ecm. So I am pretty useless when it comes to doing anything in HPtuners. I will change the maf dtc's to mil on first error and see what happens. Thank you

  4. #4
    Tuning Addict 5FDP's Avatar
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    Kinda puzzles me as to why they left it in speed density if you have a MAF sensor hooked up to this vehicle. You have it there but it's being told to never use it.

    I'd be asking them questions on that.
    2016 Silverado CCSB 5.3/6L80e, not as slow but still heavy.

    If you don't post your tune and logs when you have questions you aren't helping yourself.

  5. #5
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    I am not sure. Might have been something to do with the rpm issue?

  6. #6
    Senior Tuner
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    A faulty crank sensor or damaged crank sensor wires will cause the PO336, the poor starting, and the no tach symptoms as well.
    Make sure you have power and ground at the sensor and check continuity between the sensor output wire and the PCM.

  7. #7
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    I agree, I have checked 5volt, low reference and ground for the sensor. I will double check again. Also need to double check the pins are in the right location on the psi harness

  8. #8
    Tuner in Training
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    Just had a truck brought to me with a similar issue. Crank Signal was erratic and the truck would randomly die.. Had a PSI Harness on it as well. Crankshaft 3 wire Pigtail was the culprit, center terminal did not have a good contact. Got a GM Pigtail from the dealer and a new sensor. Good as new!

  9. #9
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    Once the car is started, it runs like a champ and hasn?t died on me, but yeah I will definitely check all the terminals and connection for the crank sensor tomorrow

  10. #10
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    Well, I went ahead and did everything you guys recommended and I still had the issue. Pulled the engine removed the crank and found out my motor has a 24 tooth reluctor wheel. Didn?t even think of checking the reluctor wheel when I bought the engine. Needless to say I will be putting a 58 tooth reluctor wheel on it shortly and that should fix all my problems. Thanks

  11. #11
    Tuning Addict 5FDP's Avatar
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    So then the cam gear will have to be changed too?

    Or is that already a 4x cam gear?
    2016 Silverado CCSB 5.3/6L80e, not as slow but still heavy.

    If you don't post your tune and logs when you have questions you aren't helping yourself.

  12. #12
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    Yeah it has the 4x cam gear.