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Thread: No STFT's or LTFT's?

  1. #1
    Tuner in Training
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    No STFT's or LTFT's?

    I'm not seeing any STFT's or LTFT's after the car is warm and above the learn temp. I also noticed my MAF is now not operating and throwing the DTC code for low frequency. Would the MAF not operating properly cause the trims to not read while logging data?

  2. #2
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    Make sure you have both front 02's operating. .. Otherwise they ain't going to log ltft.

  3. #3
    Senior Tuner
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    "None" as in =0 indicates you are faulting out of closed loop.
    "None" as in not displaying, is something like a setup deal.
    Which?

  4. #4
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    Both front O2's are working fine and bouncing from low to high mv. The scanner is showing 0 for all STFT's and LTFT's. They are enabled and set to report. So why no readings?

  5. #5
    Senior Tuner Iam Broke's Avatar
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    MAF has failed or is failed in the tune forcing SD mode.
    '12 Camaro T3 2SS/RS LS3 M6, SLP TVS 2300, Flex Fuel

  6. #6
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    Yes the MAF has failed and is throwing low frequency DTC. So that is what is causing trims to not log?

  7. #7
    Senior Tuner Iam Broke's Avatar
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    Yes.
    '12 Camaro T3 2SS/RS LS3 M6, SLP TVS 2300, Flex Fuel

  8. #8
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    Looks like I'm experiencing something very similar with a 4.8L. O2s are reading fine, but no LTFT/STFT readings. O2's are reading. Following codes are being thrown. Seeing missfires in cylinders 1 and 8 only when MAF is connected. Disconnect MAF and no misfires detected but I'm assuming it stops logging them with MAF disconnected? Seems strange it would only misfire with MAF connected. Replacedd everything on cylinder 8 (injector, coil, wires) injector shows firing fine with NOID. This is a modified stock 2005 truck wiring harness. This is with stock configuration. I tried disabling the rear 02s same results just performed a full write of stock configuration with 4L80 transmission and still LTFT don't register.

    Any help would be greatly appreciated as to where to start. I've checked grounds, and power for everything is run pretty much straight to posts that feed battery. I believe when I first started this LTFTs were logging. Not sure why they would stop logging now. This is with long tube headers through mufflers.


    [PCM] P0200 - Injector Control Circuit (Pending) (Old) (Current) (Immature)
    [PCM] P0443 - EVAP Purge Solenoid Valve 1 Control CKT (Pending) (Old) (Current) (Immature)
    [PCM] P0449 - Evaporative Emission (EVAP) Vent Solenoid Control Circuit (Pending) (Old) (Current) (Immature)
    [PCM] P0452 - Fuel Tank Pressure Sensor Circuit Low Voltage (Pending) (Old) (Current) (Immature)
    [PCM] P0463 - Fuel Level Sensor Circuit High Voltage (Pending) (Old) (Current) (Immature)
    [PCM] P0480 - Cooling Fan Relay 1 Control Circuit (Pending) (Old) (Current) (Immature)
    [PCM] P0481 - Cooling Fan Relay 2 Control Circuit (Pending) (Old) (Current) (Immature)
    [PCM] P0522 - Engine Oil Pressure Sensor/Switch Circuit Low Voltage (Pending) (Old) (History) (Current) (Immature)
    [PCM] P0650 - Malfunction Indicator Lamp (MIL) Control Circuit (Pending) (Old) (Current) (Immature)
    [PCM] P0654 - Engine RPM Output Circuit Malfunction (Pending) (Old) (History) (Current) (Immature)
    [PCM] P0740 - TCC Enable Solenoid Circuit Electrical (Pending) (Old) (Current) (Immature)
    [PCM] P2761 - Torque Converter Clutch Pressure Control Solenoid Control Circuit/Open (Pending) (Old) (Current) (Immature)

  9. #9
    I recognise this is an old thread, but in case anyone else digs it up. The PCM won't consider all requisites met for Closed Loop fuelling until the EVAP solenoid purges (or at least is commanded to purge), so a P0443 will prevent any fuel trims.