Glad I was able to help you! The G4+ ECU definitely looks like a powerful package. Have fun learning to tune it.

 

I'm trying to figure out what causes this low voltage and first thing I found is that my HKS Turbo Timer display voltage is always higher than that shown in ECU. For example while ECU was on 12.88 V the turbo timer was showing 14.10 V. But I assume ECU voltage is more accurate and I will base my assumptions on it.

So that is what I found:

• Voltage is low when the car is not running (approx. 11.8 V)
• Voltage is very low when cranking (approx. 9V). Car is struggling to start.

• When I am driving it is also low (usually around 12.8 V - 13.6 V) and it seems getting lower the longer I'm driving. I attached new log file "without_problem.llg" on https://drive.google.com/drive/folde...a5cice1SK4I24- where you can clearly see that case

Also today on my test ride I logged something very strange... My voltage was low but in one point it increased without any cause that I can recall. Then it came back to 'normal' state:



From what I can see comparing logs from ride when problem occured and one without, the difference is that my voltage doesn't rise just after cracking. Cracking voltage is always low (approx. 9V) but sometimes it 'gets up' and other time doesn't and I get my fuel cut. Am I getting it right? Here is a picture of log that I got my problem caught:



I know that it's hard to tell just from viewing my logs, but do you think it is possible that battery is broken? Or maybe alternator?

 

It could be a bad battery, a bad alternator, or bad wiring between alternator and battery or battery and ground. Do the following to check:

1. Disconnect the battery and test the voltage between positive and negative terminals with a voltmeter. It should be between 12 and 13.2 volts when fully charged. If not, it is probably bad and must be replaced.

2. Reconnect the battery and run the engine at 2k RPM. Turn on all the loads (blower on high, headlights on, rear defrost on, and so forth). Measure the charging voltage across the battery terminals, and between the big battery alternator terminal and alternator case. There are two things that you are looking for. The charging voltage across the battery should be between 13.9v to 14.4v. The voltage at the battery and the voltage at the alternator should be within 0.5v of each other. If the voltage at the battery and alternator don't match, for example the battery reads 12v and alternator reads 14v, this means that there is an issue with wiring. If the voltage at the alternator is less than 14v then you have a bad alternator.

3. While applying the same conditions as (2) above, put the black multimeter probe on the negative battery terminal (if possible dig it into the battery post, not the terminal). Put the red probe on the alternator case. You're looking for the voltage to be below about 0.5v. If the voltage is higher than that, examine all the negative cabling for problems. Preform the same test with the positive side. Place the red lead on the positive battery terminal (if possible dig it into the battery post, not the terminal). Place the black lead on the battery post of the alternator. Same thing as above, if the voltage is above 0.5v then examine the positive cabling for problems.

 

(1) I took the battery from trunk and the voltage was: 12.56 V. I went with it to shop where it was bought 3 years ago and they made test "under load" with a special device and said it is ok.

(2) I couldn't do it with 2k RPM because alternator is so deep that my friend was keeping black probe on alternator case while I was trying to put red probe on positive alternator terminal. So the test was made on idling revs but I can retry it on 2k RPM with more people if it's necessary. I put all load I could (low beams, high beams, turn signals, radio, blower on max and rear defroster) and that is what I measured:

Battery voltage under load: 14.33V
Alternator voltage under load: 14.70V

Without any load but still with engine running the battery voltage was 14.56 V and alternator was 14.76 V

(3) My battery is in the trunk and my multimeter does not have such a long wires to reach front of the car I was thinking about using jumper cables as an extension but won't it distort the results?

I have recorded the strange crackling noises while starting my engine. Before recording I started engine 3 times and the first one as always was much struggle for engine to start. Then it was just like in the video. You can hear this noise every time I start the car. Maybe it has something to do with it?

 

Battery, alternator and wiring between alternator and battery all tested good which is good news. Did you test the battery to ground cable? If not, check the resistance between the battery ground terminal and the metal of the chassis. It should be < 1 Ohm. If it is more than 1 Ohm find out where the bad earth connection is and repair it.

Next you have to find out why your G4+ ECU is not getting 14V consistently. Trace the power supply to the ECU back step by step through each wire all the way to the battery. Check the resistance of each segment of the circuit with your multi-meter. You may have an intermittent connection which his causing the voltage to drop. A resistance of more than 1 ohm in any segment of the power circuit will indicate the bad one. Replace all bad segments with a new wire and connectors. Good luck tracking it down

 

Here is how my battery looks like:



I made those test:

• between battery ground terminal and chassis ground where the cable is pinned ("Ground" in the picture)
• between battery ground terminal and chassis (metal without any paint)
• I pushed probe inside this ground cable on both sides ("Same cable" in the picture)

In every of those tests it showed 30-40 Ohm:



I don't know why but when I switch my probes (red with black) it does not show any resistance (maybe it should be like that):



I have also tested voltage in engine bay between positive terminal (that comes from battery in trunk) and ground (showed in picture), chassis, engine and others. It all showed exactly the same voltage as the battery did:



Also between those grounds that I found (in engine bay) there is no resistance.

 

The measured resistance on the battery earth is 80 Ohms (200 x 0.4) That looks like the cause of your voltage drop under load. Suggest you fix that first.

 

So.. After 1.5 year I have FINALLY solved this issue​​​​​​ ​​​

It came out that it was composed of two flaws. First of all, while analyzing logs I relized that some of my voltage drops were "stuck" on certain values and wont change at all. That was very strange since those values should always change a little. After whole day of research I found post on LinkECU forum where one guy had same problem and it was... Software bug! I updated my ECU and from that time value of voltage newer get "stuck" anymore. I was sure that will fix my issue in whole. But after some test drives the problem occured again.. Again in logs the voltage was getting lower and lower to the point when it gets under 13V and my rev limiter was triggered.

After checking battery, alternator and every possible cable with voltage supply I realized that only ECU shows lower voltage. I found in documentation that in my ECU only pin's 47 and 59 can supply voltage so I made 'backprobe' test on them. And then I really got shocked because the reading on my multimeter was different than the value in ECU



I couldn't imagine how it was possible to read different values if I was checking on 'the back' of the plug with my probe on this same cable that was connecting my ECU to voltage. I removed ECU from my car and checked those (and every other) pin for some bad grounds etc. Nothing. I honestly thought I was dealing with an error that couldn't be fix in any way and I was doomed to drive a damaged car forever But then I realized I can do one more thing... I replaced the pin with new one and... EVERYTHING STARTED TO WORK PROPERLY. I made like 100 test drives and my voltage never dropped again !!!!!!!!

I would like to thank everyone for your help, especially cdrinkh2o I don't think I would ever solve this problem without your support.

P.S. I'm going to hang this damaged pin in frame with caption "Every problem can be solved"

THE END

 

Those are the kinds of issues that make you want to push the car off a cliff. Glad you figured it out!

 

Glad you got to the bottom of this OP. I probably would have started throwing money around at that point and gone broke. New ECU, new ECU harness, all instead of a 2 dollar pin .

 

@varv Way to go tracking it down! Happy you fixed it.