Soild CEL, NO codes

Hondata model coverage & ECU application questions.
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espeedgarage
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Soild CEL, NO codes

Post by espeedgarage »

As the title states the issue is solid CEL with no codes reading while data logging, car runs and drive no issues. Just want to have a properly functioning CEL.Car is a road race car with no factory wiring, complete custom harness, all power needing items ecu, injectors, coil are on switched relay panel. No fuel main relay,, no factory fuse boxes, no eld.Try the ecu in street car and CEL functions properly, comes on for 2 sec prime then off.Try known good stock ecu in race car same solid CEL, . So from here I'm figuring something is wired incorrectly in my harness. I've pinned out my harnesses from end to end and can't find any issues.
Does the ecu have a certain power up sequence it looks for?
Do I have something tied to ground that shouldn't be?
Any ideas are greatly appreciated this one has had me stumped for months.
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Hondata
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Re: Soild CEL, NO codes

Post by Hondata »

Probably you should at least tell us what Hondata system it is and what ECU you are using.

Check the SCS is not grounded.
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espeedgarage
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Re: Soild CEL, NO codes

Post by espeedgarage »

Sorry hondata s300v3 in p28. Stock ecu used to compare p06
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Spunkster
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Re: Soild CEL, NO codes

Post by Spunkster »

If it works in another vehicle and other ECUs have the same problem, then you have a wiring issue and could be any number of things. This is why it is not a good idea to start removing things as it usually causes problems.
espeedgarage
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Re: Soild CEL, NO codes

Post by espeedgarage »

SCS pin D4 is not grounded, it is an empty pin was eliminated from harness.
Thank you spunkster for confirming what I was beginning to think. Care to elaborate on the any number of things it could be? I'm usually pretty good with diagnostic work and researching to figure it out, but this has me baffled. Hence, finally posting here to try and figure this out. I've compared my harness to multiple OBD1 honda diagrams and can't find anything out of place.
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Spunkster
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Re: Soild CEL, NO codes

Post by Spunkster »

You'll have to look at more than just the pins at the ECU as there could be a short somewhere in the harness.
espeedgarage
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Re: Soild CEL, NO codes

Post by espeedgarage »

Update
I have checked the entire harness for shorts to ground or power and found no issues.
Pins A-23,24,26 B2 (pg1,2 lg1,2)are all tied together with shield for distributor wires is all tied to ground.
Pins A25,B1, D1(igp1,2, vbu) are the only powers
Sensor ground 1,2 only have ground when ecu is plugged in.

When I was testing circuits I noticed I was able to light up my LED I was using for my MIL. Switched to a normal incandescent bulb and seemed to fix my solid MIL issue.
Does this seem right? Possibly the resistance difference between LED and bulb?

Also found that I can not force a MIL for tps or map like I can with all other sensors by unplugging them. Unplugging map causes engine to die but no MIL. Unplugging tps seems to have no effect on engine and no MIL. Both are reading proper values on hondata when data logging.
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Spunkster
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Re: Soild CEL, NO codes

Post by Spunkster »

I would recommend you not use the LED.

MAP and TPS will not generate an error code just by unplugging them under some conditions..
Shuttle
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Re: Soild CEL, NO codes

Post by Shuttle »

Hate to reopen a thread but I have this exact problem.

P28 working fine: 02D01720-1500
s300 V1 fitted 11,105
working fine on bench with test harness
SCS postion detected in dataloging, MIL shown on screen and in harness when create fault.


P28 with solid CEL: 02d011F0-1500
The same S300 fitted
the same test harness
MIL off in datalog but on solid in harness
SCS detection not working in datalog, but, when switched on it will show the codes both in datalog AND on the test harness.

If I remove J1, MIL functions normally in the harness.

ECU is a remanufactured one, everything is pristine.

Would you have any suggestions please ?
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Spunkster
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Re: Soild CEL, NO codes

Post by Spunkster »

are you using an LED?
EkanemJoseph
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Re: Soild CEL, NO codes

Post by EkanemJoseph »

It looks like a future problem may be an improper connection to some item in the future wiring harness. If all the wires have been checked and connected correctly, it is possible that the cause may be related to various control unit (ECU). In some cases, if the ECU is not receiving certain data from sensors or other elements, the CEL may remain on even though the vehicle itself is operating normally. Regarding the ECU conclusion, it should be noted that all control units operate on the basis of algorithms and software that determine how various sensors and other elements are operated and checked. Typically, the procedure for starting the ECU involves checking the various systems and subsystems, as well as running self-diagnostic tests, which can take several seconds to complete. However, without access to the specific documentation and software for your vehicle, it is difficult to say exactly what procedures and sequences involve your ECU.
Shuttle
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Re: Soild CEL, NO codes

Post by Shuttle »

Spunkster wrote: Thu Mar 23, 2023 9:03 am are you using an LED?
Nope, a bulb taken out of an old honda cluster. :)
The test wiring harness is 100% fine.
The connectors are modified to remove the retaining clips and they are clamped into the ECU being tested.

Now here is the weird thing. I managed to get it to stop doing it.
In SManager I clicked through the menus and disabled spool valve check.
It wasn't coding for this anyway. But hey why not, right? (When all the others on misc page are already ticked)
And it wasn't checked for the working ECU.

But after doing that, I can't get the solid CEL to come back on again.
Even if I re-enable the spool check.
So.... fixed? but whaaa ?
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