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  • 1996 - 2004 SN95 Mustang -General/Talk-
  • SN95 4.6L Mustang Tech

Gauge Cluster "sweeps" ONLY when datalogging with SCT X4

  • Thread starter Thread starter FlyinRyan02
  • Start date Start date Aug 14, 2023
F

FlyinRyan02

New Member
Aug 14, 2023
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1
Pembroke, NH
Aug 14, 2023
#1
  • Aug 14, 2023
  • #1
Hey guys,

VERY first post here so I apologize if this has been discussed before but I haven't found anything similar yet. But just for a little background on what's done to the car first...

Car: 2004 Mustang GT
Promaxx Heads
MHS Cams
Procharger D1SC
AEM V3 Water/Meth
Dual 340lph Full Return fuel system
10.5:1

I am having an issue that ONLY when I select "start datalog" on the SCT X4 or even when I have LiveLink connected to the X4, mid-pull at 5500 RPM the gauge cluster sweeps (as if you just turned the key off then back on)...causing a loss of data (flatlines during that moment). Mainly what I first look at is the RPM PID. You can see during the curve (WOT pull 3rd gear) that it flatlines at 5500 and also at around 6200. When I am NOT datalogging, even with the unit plugged in, the car is flawless....no issues. The car used to have no issue with quality logs that I send them to and receive updated tunes. I replaced a P1SC with a D1SC and replaced the alternator with a stock replacement 130A alternator. Tried reversing anything I could think of that could cause this issue but the alternator is functioning perfect and swapping blowers should also not cause this issue. Car has a soft tune on it for the D1SC and runs flawless. I have spoken to SCT and the unit is fully updated and has been wiped with new firmware as well. I have tried another OBDII to X4 cable as well (do not know the condition of that cable but both look amazing).

Why would this be happening ONLY when I press "start datalog" or recording? I have purchased a different ECU (My tuner will disable PATS) that is on the way to see if something got messed up there but definitely a weird issue...any help is appreciated! I will keep you updated if the ECU swap changes anything

Included is a picture of the car and a datalog showing the flatlines...RPM is the blue line and the orange is the battery voltage. When this happens and the gauge sweeps, the car also does feel fine. No bucking or anything.
 

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