Problem Writing Flash - Reads just fine

First off, love the product. It successfully solved some issues I had with the car and now it's 1000% more drivable.

So far I've only been able to successfully write a tune two times. First time I downloaded the VCM stable suite. After syncing the MPVI2, it downloaded the latest firmware. I read the PCM with no problems. Changed a few things, and chose Write-Calibration. It uploaded fine, cranked up, and I drove around for 30min. After coming back the next day, I tried to Write-Calibration again with a few more changes. This time it got stuck at 0% and said timed out. I then tried the following.

• High speed / regular modes
• Uninstalled and reinstalled VCM
• Different USB ports
• Restarted computer
• Disabled / re-enabled USB in device manager
• Resynced interface
• Pulled all lights/radio fuses
• Pulled fuel pump fuse
• Waited 15+ seconds after turning key to on
• Drank beer, waited 30 minutes, and tried all above again

I was doing some reading and saw that some people had better luck with the Beta. After installing that, I tried to Write-Calibration again. No luck. Immediately after the time out error, I unchecked the High Speed option and tried again. This time is worked, successful write that took about 2min. Unfortunately during all subsequent attempts it continued to throw time out errors like the first time. I've tried about 20 times with different conditions with no luck. Any suggestions? See attached for HPT file. Attachment 97739


Setup:
5.7L Ls1 from fbody
Datsun 280z
New alternator, battery
Showing 12.5v with ignition on

ID: 2060502641
HardwareVersion: 1.4.0
ManufactureDate: 2/21/2019 4:43:35 PM
PartNumber: 6230
FirmwareVersion: 3.0.30

Usually this ends up being a wiring thing. I don't think you are having any problems with the file itself or anything like that.

Sometimes people have to end up using a bench harness because the wiring in the car doesn't like to work right all the time.

Is the harness and the OBD2 wiring from the F-body car too? At this point it probably is 20 years old.

Previous owner did the swap. Looks like a cleaned up Fbody harness. That would be slightly annoying, but I'll do it if that's the only option. It's strange that it worked that one time.

Follow up, where did the ""O2 Readiness ECT" menu go in this version of VCM? I see screenshots online, but this one doesn't appear to have it?

That table is on newer computers.

This P01 won't have that. You can change the open to closed loop temp settings and also change the STFT and LTFT settings. It looks like you've set the tune up for open loop at the moment. If that is what you are after you still have to change the open loop EQ ratio to 1.00 after 140 degree coolant temp, this way it commands stoich when warm. Then all your tuning changes for the MAF/VE will not be skewed while tuning with a wideband.

Thanks for the input. I went ahead and ordered a bench harness kit.

I'm running in OL because of some strangeness in the narrowband O2 sensors. I replaced the Bank 1 sensor with three different units and even repinned the weatherpack connector. Nothing solved the random fluctuating signal I'm getting on that channel. I even ohmed out the harness all the way to the PCM and it looks fine. I'm suspecting that I went through a puddle and it caused some sort of internal short in the PCM. I seem to remember problems after I went through one that was exhaust level.

What's odd is that even with the current tune, it still randomly puts itself back into closed loop mode. Of course when it sees the flatlined signal on the O2 bank 1 channel it immediately sets STFT to -40%. How can I more strictly enforce the open loop command? When I'm running VCM scanner I can go in and command closed loop off. That works great, but driving around with the laptop is getting old.

The tune posted above should never enter closed loop on it's own. If the closed loop ECT vs IAT is set to 284 degrees, it should never enter closed loop. Same with having the LTFT set to 284 and the STFT set to disabled.

If that tune is flashed in, it should stay in open loop forever without fuel trims.

Here is the log where it randomly goes CL. Attachment 97742Attachment 97743


Should be impossible right? I read the tune back and looked at it in Editor, it looks like everything wrote correctly.

Something screwy with this PCM perhaps. 25 volts seems a touch high. Any got a spare 512k PCM they want to loam me? Attachment 97763

Spare PCM's are cheap in the yards. Going for $38 around here. Its good to have a spare or two for diagnostic purposes.

Rick

Got the bench harness in, same result. Does this indicate a problem with the MPVI2 or the PCM? I'm really not thrilled about having to buy more credits simply to try this again on the spare.

Please open a support ticket here: https://support.hptuners.com/

We'll be able to further assist you.