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Thread: No Start - RPM dropping to zero + Diag 6 errors.

  1. #1

    Default No Start - RPM dropping to zero + Diag 6 errors.

    Hello. I tried to start my Terminator X Max for the first time today. The engine is an LS2 from a 2006 GTO which is kind of a weird setup. Engine is laid out like an LS3, but uses 24x/1x crank/cam sensors. The harness I'm using is an LS3. I've repinned the cam sensor wiring per this Holley video and swapped the crank sensor plug. I have triple checked this.

    However there's another difference which is not discussed in the video, which is that 24x/1x sensors work on +12v. Some people (including Holley) claim that 24x/1x sensors will work on +5V provided by the LS3 crank/cam wiring, but I suspect this might be my issue. As you can see from the datalog below, I'm getting RPM signal during cranking, but the signal drops to zero and Diag #6 error count increases at that time. I know these errors are an issue during normal operation, but it's not clear what I should expect during cranking.

    The only other potential issue I can see is that my DBW TPS will not read 0 with no pedal input, the lowest value I have seen is 17. You can see me actuating the throttle during cranking, trying to get air into the engine, and the value falls back down to 17. Can anyone please chime in? I'd like to know what expected RPM and error values should be during cranking, before I go down the route of repinning my crank/cam for +12V. My fuel pressure and power delivery are both solid as can be.



    My issue seems fairly similar to this post: https://forums.holley.com/showthread...-when-cranking. I've ordered the appropriate SuperSeal pins and will run a separate +12V wire from B20 to the cam & crank to test this out.

    I couldn't wait so I got creative. I hijacked PWM#4 output on B10 from the I/O harness and moved it to B20, and used that to run +12V to cam & crank. Car started this time! But wants to die without throttle and datalogs show I'm still losing RPM signal at the same time Diag 6 events are generated. I've attached my datalog for anyone that could have a look. termx_000101-001206-0004-firststart.dl.zip
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  2. #2
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    Download Holley EFI V4 and then open it and go to the Help section and compare the differences between a LS1 & LS2 wiring harness. You may see what you have wrong.

  3. #3

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    I can’t imagine there is anything in a wiring diagram that will help me, at least as it relates to this issue. The only difference in the harness should be +5V vs +12V to cam/crank sensor and reversed A/C pins on cam, all of which I’ve done.

  4. #4
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    And they use a different ground.

  5. #5

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    Wow, good eye. I see that the LS1 harnesses use a shielded IPU ground versus the common sensor ground. So we’re further away from Holley’s claim that 58x works on 24x engines with a simple pin swap, but it’s something. I could see poor shielding creating some intermittent sensor errors like I see in the datalog. So, how could I run a good IPU ground to these sensors for testing? I consider myself pretty good with wiring, but I'm not well versed in shielding best practices. I'm considering having Holley send me the LS1 harness to try at this point.

    I’m trying to make sense of the LS1 vs LS2 wiring diagrams. On the LS1 diagrams, the cam/crank ground sensors both go to A14 ‘IPU Ground’. There's also a line that connects both of these sensor, back to the same A14 ground. It's not clear to me how they are connected, or what the function is.



    On the LS2 diagrams, the cam/crank grounds go to A18 ‘Sensor Ground’ shared by the rest of the engine sensors. The A14 ‘IPU Ground’ apparently runs to a pair of ‘shield grounds’ that exist separate, not tied into anything? Can someone please help me understand?


  6. #6
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    Quote Originally Posted by wompa View Post
    I’m trying to make sense of the LS1 vs LS2 wiring diagrams. On the LS1 diagrams, the cam/crank ground sensors both go to A14 ‘IPU Ground’. There's also a line that connects both of these sensor, back to the same A14 ground. It's not clear to me how they are connected, or what the function is. On the LS2 diagrams, the cam/crank grounds go to A18 ‘Sensor Ground’ shared by the rest of the engine sensors.
    Why can't you LSx guys just wire your crank & cam sensors exactly as shown in the Holley EFI Wiring Manual?
    +12V LS1 Crank & Cam Sensors, Figure 24, Page 37: http://documents.holley.com/techlibr...10555rev17.pdf (Holley EFI Wiring Manual - Section 13, Wiring Appendix)
    +5V LS2 Crank & Cam Sensors, Figure 22, Page 35: http://documents.holley.com/techlibr...10555rev17.pdf (Holley EFI Wiring Manual - Section 13, Wiring Appendix)
    Everything you need to know is in Step #6: http://forums.holley.com/showthread....ents-Read-This (Initial Checks & Adjustments - Read Steps #1-#6!)
    https://www.youtube.com/watch?v=OChfI5i2S3Y (How To Use Holley EFI 24x & 58x LSx Main Harnesses)

    Quote Originally Posted by wompa View Post
    The A14 ‘IPU Ground’ apparently runs to a pair of ‘shield grounds’ that exist separate, not tied into anything? Can someone please help me understand?
    Think of the shield wire as an antenna pointing to the sensor; it's only supposed to be grounded at the ECU end.
    http://www.newark.com/pdfs/techartic...haWire/USC.pdf (Shielded Wiring - "Drain Wire", Page 2 & 3)
    May God's grace bless you in the Lord Jesus Christ.
    '92 Ford Mustang GT: 385" SBF, Dart SHP 8.2 block, TFS TW 11R 205 heads, 11.8:1 comp, TFS R-Series intake, Dominator MPFI & DIS, 36-1 crank trigger/1x cam sync, 160A 3G alternator, Optima Red battery, A/C, 100HP progressive dry direct-port NOS, Spal dual 12" fans/3-core Frostbite aluminum radiator, Pypes dual 2.5" exhaust/off-road X-pipe/shorty headers, S&W subframe connectors, LenTech Strip Terminator wide-ratio AOD/2800 RPM converter, M4602G aluminum driveshaft, FRPP 3.31 gears, Cobra Trac-Lok differential, Moser 31 spline axles, '04 Cobra 4-disc brakes, '93 Cobra booster & M/C, 5-lug Bullitt wheels & 245/45R17 tires.

  7. #7

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    Quote Originally Posted by Danny Cabral View Post
    Why can't you LSx guys just wire your crank & cam sensors exactly as shown in the Holley EFI Wiring Manual?
    +12V LS1 Crank & Cam Sensors, Figure 24, Page 37: http://documents.holley.com/techlibr...10555rev17.pdf (Holley EFI Wiring Manual - Section 13, Wiring Appendix)
    +5V LS2 Crank & Cam Sensors, Figure 22, Page 35: http://documents.holley.com/techlibr...10555rev17.pdf (Holley EFI Wiring Manual - Section 13, Wiring Appendix)
    Everything you need to know is in Step #6: http://forums.holley.com/showthread....ents-Read-This (Initial Checks & Adjustments - Read Steps #1-#6!)
    https://www.youtube.com/watch?v=OChfI5i2S3Y (How To Use Holley EFI 24x & 58x LSx Main Harnesses)
    My sensors are wired exactly as shown in the manual. I'm using Holley's LS3 harness. The reason I'm messing with wiring at all is because things aren't working and my '06 GTO LS2 is kind of nonstandard. Everything is laid out like LS3 (front cam sensor, knock sensors at bottom of the block) except it uses 24x/1x sensors which operate on +12V. Holley claims the sensors will operate on +5V, but since I'm having issues with the crank signal, I'm trying to give them the power they expect.

    Think of the shield wire as an antenna pointing to the sensor; it's only supposed to be grounded at the ECU end.
    http://www.newark.com/pdfs/techartic...haWire/USC.pdf (Shielded Wiring - "Drain Wire", Page 2 & 3)
    I've come across this post several times. Why does the Holley LS1 harness have cam/crank sensors tied into this ground?

    I did some more thinking and the crank sensor wiring branch is in a pretty noisy area. It runs in parallel with a 2 AWG starter cable, sits close to the #8 plug wire and snakes across the top of the starter motor, probably hell for a sensitive pickup.

    I'll experiment more with routing and see what I can do to improve things and take another datalog. At least I'm getting good at pulling the starter.
    UPDATE: I've rerouted my crank sensor back towards the bellhousing, as far away from any sources of interference that I can, and I'm back to no start. Just getting random pops and backfires and never catches. Extremely frustrating experience so far. termx_000101-000546-0008-nostart.zip termx_000101-000546-0008-nostart.zip


  8. #8
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    I can tell from your Battery trace that you were cranking, but look at your RPM trace. You need to find out why it's losing the RPM signal. Have you taken a System Log to look at your Cam & Crank sensors?

  9. #9

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    Terminator X is not capable of producing a System Log, only a datalog. I was trying to figure out how to do it this weekend, it does not appear in the datalog menu and I confirmed with a Holley tech just now that it can’t do it.

    The tech I spoke with informed me that my diag #6 CRANK_ERROR_count increasing during starting was not normal/acceptable and that I should order a new crank sensor. It would explain the loss of RPM signal that I'm seeing. I'm a bit skeptical that throwing parts at it will fix the problem given the car ran perfectly on the stock PCM but we'll see.

    He did not think it was likely related to EMI. I have a new sensor coming overnight and will report back tomorrow.

    Brand new ACDelco crank sensor arrived from Summit this morning. I threw it in and it fired right up, still running terribly and wants to die without throttle. CRANK_ERROR_counts are still showing up in the datalog and RPM reading drops to zero.
    termx_000101-000010-0009-start.zip

  10. #10
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    Always post your current Config File with your datalogs.

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