Page 1 of 1

ECU Shutting Down

Posted: Wed Jan 03, 2018 8:44 am
by CoolTech
Since March we have been in the process of building a track-dedicated car (Exocet chassis) and we are running a K24A2 with the Hondata engine controller. We spent several hours on the dyno (first time tuning a Honda) and had good success building a reasonable tune. Full disclosure (and maybe a key): Subsequent to the dyno and before putting the car on the track, my son attempted to build a signal converter to adapt the Miata transmission VSS signal to a signal that the K-pro could use. He used one of the 5v wires and he also (obviously) connected to the VSS signal in.

On the track, the VSS signal circuit he devised didn't work (so, that circuit is immediately suspect.) First few laps on the road course were without incident... maybe 15 minutes of total time. Everything was working fine - just no VSS signal but we really didn't care at that point. Back out on the track and within a few minutes, the driver experienced a brief "dead pedal" that was more or less momentary. About a minute later the ECU shutdown for a couple of seconds and driver went immediately clutch-in. Pressing of the start-button and the car immediately re-fired and acted normal. He pitted and we checked the car over - of course inspecting grounds and fuses. All looked good. Car started fine and we sent him back out. Within just a few minutes, the car died again on-track and this time would not re-start. (I was relieved somewhat as I prefer hard failures over intermittent problems any day!!)

We took the car back to the garage for closer inspection and to isolate the problem. Once again we reviewed/inspected our grounds - one at the timing cover, one up at the injectors onto the valve cover and we have one between the block and chassis. All good. Further, all fuses are good and we verified that the ECU had power and ground. (Verified at ECU with cover off.)

We are using the MIL indicator connected to an LED on our switch panel. It works well and alerted us to a fault code (unrelated) during one of our dyno sessions. Well, when we turn the ignition on, normally the MIL indicator will illuminate until the engine is started and then promptly turns off. With this "dead ECU" problem, the MIL does not illuminate and the ECU also will not give a fuel pump on signal as it normally does at first key-on. Further, we could not connect with the ECU through the USB. (Mind you, we validated that the ECU absolutely has power/ground.) We disconnected our home-made VSS circuitry. (We also have a master battery off switch and we had that off for "awhile" and turning it back on - we had the same symptoms. No MIL light at ignition-on and no 3-second fuel pump run.

Our conclusion is that we had somehow killed the ECU. We put the car on the trailer and brought it home - the entire 4-hour trip speculating on what could have been the problem. Our guess was that the VSS circuit had either managed to short the 5v signal wire and/or given some kind of unexpected signal over the VSS input. We would have to call Hondata and see about getting the ECU repaired.

A day later we are back at home with the car and I'm doing something else when I turn on the master battery on switch and then flick on the ignition switch. I hear the fuel pump run for 3-seconds and I notice the MIL is illuminating "normally" at key-on. WTF? I press the Start button and she immediately fires up and runs like nothing has happened. We connect to the USB and have full communication (and no fault codes).

So, sorry for the long post. As you might tell, our strongest suspicion is our VSS circuitry caused the havoc. But, I'm also looking for other ideas or things we can try. I don't want to get over-confident that we have fixed the problem and then get all the way back out to the track and have the same symptoms (of course we have removed all of our VSS connections). Is there anything else we can/should be looking at? Thanks so much for any comments/advice!!

Re: ECU Shutting Down

Posted: Wed Jan 03, 2018 10:24 am
by Spunkster
You need to try the ECU in a known working vehicle as it does not sound like an ECU issue, but some intermittent fault in the wiring, fuses or relays.

Re: ECU Shutting Down

Posted: Wed Jan 03, 2018 10:55 am
by CoolTech
Spunkster - I very much appreciate you attention to responses and how fast you are to support your products.

We will definitely investigate. Wiring is all relatively straightforward in our application. Engine harness side is pretty much all OEM. Body side, is pretty much all us. What troubles me is that during "hard fault" when ECU was acting dead (no MIL lamp at key-on and no fuel pump 3-sec run), we measured 12v at ECU as well as continuity to good ground..... at least we *think* we did! Main relay was cycling on and off with key-on (as it should) but acted like ECU didn't want to activate MIL lamp or fuel pump. Sounds crazy, I know...... will continue to diagnose but of course everything is acting fine now. Grrrrrr... (lol)


Re: ECU Shutting Down

Posted: Tue Feb 20, 2018 10:33 am
by CoolTech
We continue to have this same proble, We have had the race car to the track 3 times now and the scenario is always the same. At the track, the first 2 ~20 minute sessions are just flawless. The car runs great and driver is able to push the car hard. Approximately 20-60 minutes between session. Typically in 3rd session, we will experience an ECU shutdown. ECU seems to physically shut-down but cycling ignition will allow a re-start. Once "problem" has started - it typically will get worse (happens more frequent/easily) - definitely within first couple of minutes of attempting to drive. On third session of first time at track, "problem" was so bad, car would crank over but wouldn't fire-up. Trailer car home the next day (figuring hard fault in ECU) but car started right up at home.

At second track outing - once again first two sessions were flawless. In third session, noticed some stumbling. In forth session, car wouldn't go a single lap without dying. Again, once "problem" appears - it seems to get worse/more frequent. Trailered car home again. At home, replaced main relay. Re-wired fuel pump relay so that "high-side" was fed from dedicated circuit/fuse based on advice from KMiata. (The theory was that fuel pump might make such high demands that ECU voltage on same circuit/wire might drop too low.) Optimistic, we took car to NASA Chuckwalla event

At third track outing - first two drive sessions were once again flawless. High spirits as we think we have problem solved. After 90 minute break, took car out for third session. After first lap, car stumbles and appears to go into LIMP mode with CEL on. Nurse car off of track. Pull codes.

1) 17-1 P0500 VSS Malfunction
Daughter board communication error (battery voltage low when cranking)

We clear the codes. We disconnect VSS wire to ECU and turn off VSS in ECU. (Thought was that we are providing bad VSS signal through square-wave converter board.) Car starts normally.

Take car to grid for 4th session. Start to accelerate car out of grid and it dies. Cycle ignition and car re-starts normally.
GRRRRRRRRRRRRRRRRRRRRRRRRRRR! No codes stored. Car starts and idles just fine back to pit area.

Desperately want to run this car at NASA WERC endurance race March 9 at Willow Springs - and all 2018 WERC races. (Ultimately we want to enter 25-hours of Thunderhill.)

It is impractical for us to try this ECU in another car. We can send ECU in if we can get reasonable turn-around time. Not looking for any freebies - just want to get to root of problem.

Note that the charging system/battery in the race car seems completely fine/normal. We have never had the car on a battery tender or charger and a testament that the start/charging system all seems fine. In other words, we DO NOT charge or mess with the electrical system between outings - it just appears that "rest" seems to do the problem well.

VERY MUCH appreciate any ideas and/or suggestions!!!!!!

Re: ECU Shutting Down

Posted: Tue Feb 20, 2018 12:00 pm
by Spunkster
Based on what you have described it does not sound like an issue with the ECU or the K-Pro. It sounds like a wiring issue that is causing the voltage to drop. The daughterboard communication error indicates that there is low voltage when cranking which could mean that something is loose/heat soaking and getting an intermittent fault.

This is not the kind of thing that we will be able to see by sending it to us. The fact that it works normally for so long before the issue arises and then is fine the next day only reaffirms this.

You may also want to look at the wiring for the VSS as it sounds like it may be getting hot or shorting out and could also be the cause if all the other issues.

Re: ECU Shutting Down

Posted: Tue Feb 20, 2018 4:48 pm
by CoolTech
VERY much appreciate your response.

It is the case that everything works fine... at first, and then goes South. Just as it seems to eliminate the ECU/Hondata, for the same reason it also seems to exonerate the wiring. ALL is good at first. (Not trying at all to be argumentative.) The car is NOT fine the next day. We had the EXACT same problems at the START of day 2 after the car sat overnight. For whatever reason, a couple of trailer rides and weeks later, THEN the cycle seems to start again. For the reason that the car sits overnight (with main power OFF) leads me to believe it is NOT a heat issue.

The *only* thing that seems to make sense to me is a cracked PCB and/or component..... I don't know, I am grasping at straws. Starter/charging system seems fine. Since we completed the build, the car has NEVER been on any kind of charger. We simply have NEVER had any kind of battery or charging issue. Further, 100% of the time the car is on the AiM is datalogging and battery/ECU voltage is always good. I do have a couple of specific questions.

1. If the daughter board communication error is tripped during start-up, will that cause problems during that drive cycle? In other words, does that somehow inhibit proper initialization and will cause problems?

2. Typically, when we encounter the problem, the CANBUS output ceases. The AiM sees absolutely no data to display/record. Is that some kind of hint?

Any recommendations on next steps would be greatly appreciated.

Re: ECU Shutting Down

Posted: Tue Feb 20, 2018 5:05 pm
by Spunkster
What is the battery voltage when cranking, measured with a multi-meter at the ECU pins?

If you have a daughterboard communication issue then you have had low voltage and it will continue to have issues until the power is reset, or you re-upload the calibration with proper battery voltage.

Re: ECU Shutting Down

Posted: Tue Feb 20, 2018 9:33 pm
by CoolTech
Spunkster - thanks for your help.

Just tried the test you suggested. Removed cover from ECU so I could easily get at ECU pins.

Very cold start - hasn't been fired since Sunday...

12.2 V at ECU pin with ignition on
10.0 (and maybe even a 9.X) during cranking
14.2 as soon as engine fires

Using a Fluke 77 (digital voltmeter). Engine (unfortunately) starts pretty quickly - but I think I briefly saw a 9.X value flash right before she fired.

Please let me know your recommendation.

Re: ECU Shutting Down

Posted: Tue Feb 20, 2018 9:45 pm
by CoolTech
Battery is an Odyssey PC925. AGM

Re: ECU Shutting Down

Posted: Wed Feb 21, 2018 11:12 am
by Spunkster
Those batteries are notorious for low voltage and not holding a charge very well. I would recommend a deka battery such as the Deka ETX20L. They have better cold cranking amps and hold a charge better.

Re: ECU Shutting Down

Posted: Wed Feb 21, 2018 11:30 am
by CoolTech
Spunkster - thanks again for your help. Do you think that there is a good chance that this may be at the root of the problems we have been having??

Re: ECU Shutting Down

Posted: Wed Feb 21, 2018 11:46 am
by Spunkster
It is a good place to start.

Re: ECU Shutting Down

Posted: Thu Feb 22, 2018 1:58 am
by Arno
Could a high or (partial) AC voltage also cause the ECU to cut out? Eg. voltage regulator or rectifier on the alternator developing an issue (often heat and vibration) and sometimes letting the voltage spike or not rectifying the AC completely anymore?

Might also be a good idea to let the Kpro (if it's a V3 or later) automatically datalog to the internal flash. Can perhaps show up some things when downloading these afterwards. By tweaking the start/stop trigger events and perhaps reducing the samplerate you can get quite a decent runtime in the datalog flash for later examination/download after a run.

If that's not enough data or too low samplerate then with a Kpro V4 I guess you could even let some bluetooth enabled device (smartphone?) datalog externally or with a V3 (or earlier) you could perhaps stash a simple win7 netbook in the car with an USB connection to the ECU and let it record..

That way you should hopefully get more data on any events or trends before the ECU gives up and find the root cause of the issue.

Bye, Arno.

Re: ECU Shutting Down

Posted: Thu Feb 22, 2018 2:18 pm
by CoolTech
From what I remember finding on the internet and I believe the way the KMiata swap wiring is supplied, this is the circuit that is advocated (and which we used - originally.


Notice that the single 12v "in" wire (Fuse 6 in our case) supplies low and high side power for both relays. Our 12v in come from a Painless relay/fuse integrated panel and either due to the wire gauge or all the internal routing, seems to have less voltage at static and cranking.

The image below represent how we have re-wired and intend to test. We are now supplying 12.8v to the ECU static, 14.2 at run, and 10.8v during cranking. Additionally, we can fuse the inputs for the ECU and fuel pump independently (and correctly). Any comments are appreciated.


Re: ECU Shutting Down

Posted: Sat Mar 03, 2018 8:44 pm
by CoolTech
After the suggestions to improve voltage to the ECU during cranking - I was able to do that quite easily. But, not having full confidence - and know that each time we iterate we essentially miss another race venue, I decided to replace the ECU/K-Pro with another one. Went to the dyno today to get our class certification pulls... and the DAMN CAR DIED going through the gears on the dyno. UGhhh! We un-strapped and trailered it home.

The good news is that at home (with all of our tools available), we were able to recreate the problem and to get the ECU into a state where it just wouldn't start. (When this happens the CEL is kind of flickering like it is not getting consistent voltage.) To make a LONG story short... we FOUND IT!

Turns out we had one of the main engine harnesses running across the back of the engines. For whatever the reason (our big oversight) this was probably the only harness in the car that was not in a protective plastic loom. The harness had crossed across the sharp hex edge of the water temperature sensor. As soon as my son touched (lifted) the harness, all was restored to normal! Turning the harness over and using a large magnifying glass, we could see the glint of copper wire. JEEEEZZZ! It was an easy enough of a fix. We taped up the two wires that were damaged, put everything in a protective loom and then we re-routed the loom away from that sensor. Holy cow it feels good to finally find this SOB!!!