ECMlink Old alternator went bad, now several sensor readings are erratic

[allezgrand]

• Running ECM Link V3
• The regulator on my old alternator was bad and the alternator was spiking up to 19.5 volts at times. I replaced it with a high output (150A) BNR alternator.
• Fuel and temp gauges stopped working properly - I created a dedicated ground for them from the dash and now they work properly
• GM Style 4 bar sensor became erratic and the car wouldn't start a couple of times. It became stuck low. I was running Speed Density with GMIAT.
• I switched back to 3.5" GM MAF and RPM signal and MAF signal became erratic.
• I pulled the ECU and didn't find any visually noticeable damage (e.g. capacitor leakage, delamination, bad coating, etc.)
• GM MAF is grounded directly to chassis
• CAS is still on stock harness

At this point, I'm not sure if there may be a bad voltage regulator on the ECU, or if there's something else I'm missing.

Attached is a log showing the erratic RPM and MAF signal. Take a look at 228 seconds in. It started bucking violently around 4k rpm, then you can see the signals go haywire.
Also attached is a log from a couple days earlier when it was idling, died, then wouldn't start (MAF was not present and it was running SD). You can see the 4 bar sensor crap out at 23 seconds.

Full disclosure, I did a rush attempt at learned SD many years ago and never spent enough time to fully and properly learn how to optimize with ECMLink, so I suspect there are some gross inadequacies. Maybe someday I'll take the time to learn it properly now that there are so many resources.

Anybody have any ideas/ suggestions for what else would be worth investigating?

 

[steve]

I only looked at the first log and there are few things that popped out. First your TPS idle voltage is low and your IPS isn't working consistantly. Second is your using a Omni 4 bar MAP sensor which lately has been having a rash of failures and yours seems to go crazy. Third your VSS is broken.

I can't comment on your SD maps or settings other than to say they look unusual.

 

[allezgrand]

Thanks! I'll try to chase down the ISP, TPS, and VSS issues. I'm still logging but no longer using the MAP reading. On the second log, I switched back to the 3.5" GM MAF and then I started seeing the erratic RPM and MAF log.

Are there members on here who do remote ECM Link tuning?

 

[steve]

Sorry the files showed up with the later log being first, so it was erratic RPM and MAF log.2023.02.17-06 that I was looking at.

 

[habitatguy187]

Thanks! I'll try to chase down the ISP, TPS, and VSS issues.
Are there members on here who do remote ECM Link tuning?

Almost 20yr member I’m sure we can help you out.

I will say that the car won’t run right without the vss working properly. I would start there.

 

[allezgrand]

TPS and Idle switch both adjusted and working well now.
Regarding the VSS, my speedo is working just fine, but after looking at the log again, there appear to be times when it isn't. Where does the ECU pull a signal from the VSS? Is it pulling that at the cluster? If so, how can the speedometer be working properly and the VSS be bad? Or is there another sensor beyond just the cable in the VSS?

Any recommendations for a reliable VSS? I'm not seeing any 1G's in nearby pull it yourself junk yards.

 

[DSMPT]

how can the speedometer be working properly and the VSS be bad? Or is there another sensor beyond just the cable in the VSS?

The speedometer is mechanical cable driven, so it should still work even you have a bad reed switch for VSS signal/pulse or some issue unless it's related to the speedometer mechanism.

Any recommendations for a reliable VSS? I'm not seeing any 1G's in nearby pull it yourself junk yards.

I have been running like the one in the pic below on my 1g. That allows you to run the factory cable driven speedometer, in case if you want to keep the factory speedometer.
It's just I can't be 100% sure if it works with a factory ECU box. I use it on AEM V2 because the AEM V2 doesn't work well with 1g factory VSS signal. I guess it would work with a factory ECU since it works properly with DSM VSS parameters on AEM software though.

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[steve]

Where does the ECU pull a signal from the VSS? Is it pulling that at the cluster? If so, how can the speedometer be working properly and the VSS be bad? Or is there another sensor beyond just the cable in the VSS?

The 1G VSS is generated by a reed switch inside the speedometer and a magnet that spins causing the switch to open and close. The ECU provides a voltage that the VSS grounds to create a waveform. The Cruise Control and TCU also look at it. If they malfunction of the wiring to them shorts to ground the VSS Signal can fail.

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[allezgrand]

Thanks, Steve, that's super helpful. Given that other gauges were failing recently following over voltage from the alternator, I suspect there's a similar issue with the vss signal. I'll open it up to take a look.