Holley hp efi computer and obd2 inspection
12 Second Club
Joined: Jan 2003
Posts: 303
Likes: 2
From: Buffalo NY
Most likely you turned off a bunch of the evap codes but missed one.
I'm not talking about EVAP codes that threw a SES after it was removed im talking about every code with EVAP in the name.
I'm not talking about EVAP codes that threw a SES after it was removed im talking about every code with EVAP in the name.
Last edited by mshadow; Jan 6, 2016 at 10:26 AM.
9 Second Club
Joined: Nov 2003
Posts: 13,616
Likes: 185
From: Norn Iron
You dont feed the stock PCM some inputs, you leave it as it was with all the information it normally receives.
You only feed the aftermarket ecu the info it needs to do the jobs you want it to do. As far as the piggyback goes in it's most basic form all you would remove from the stock ecu are 8 injectors and 8 coils. That gives you total control via the standalone over all fuel/spark delivery
Above and beyond that you can of course remove other controls from the OEM ecu whether it's idle, fans, throttle if DBW etc etc. But you do not need to. It's entirely your choice.
Things like boost control, nitrous etc etc are in no way integrated with the OEM ecu anyway so are irrelevant. That's tied only to the aftermarket ecu.
It can be as simple or difficult as you want to make it depend on what controls you want for each system.
TECH Fanatic
Joined: Sep 2013
Posts: 1,001
Likes: 123
From: Mechanicsburg, PA
If, as stated, the NY test is a "key on engine off" code and monitor check, that is awesome and simple. You should only need powers, grounds for the ECM/PCM and the wires to the DLC. If someone can turn ALL the trouble codes to "Do Not Report" the monitors should show ready for testing. I'm sure I'm forgetting something and definitely have no experience with HPT. But I have had cars at my shop with systems missing that the monitor reported ready. So I think this is possible and will be simple for you. Looking forward to your resolution!
12 Second Club
Joined: Jan 2003
Posts: 303
Likes: 2
From: Buffalo NY
You run whatever harness you decide to run or build regardless of who's system it is, and of course it needs tailored to the application in hand.
You dont feed the stock PCM some inputs, you leave it as it was with all the information it normally receives.
You only feed the aftermarket ecu the info it needs to do the jobs you want it to do. As far as the piggyback goes in it's most basic form all you would remove from the stock ecu are 8 injectors and 8 coils. That gives you total control via the standalone over all fuel/spark delivery
Above and beyond that you can of course remove other controls from the OEM ecu whether it's idle, fans, throttle if DBW etc etc. But you do not need to. It's entirely your choice.
Things like boost control, nitrous etc etc are in no way integrated with the OEM ecu anyway so are irrelevant. That's tied only to the aftermarket ecu.
It can be as simple or difficult as you want to make it depend on what controls you want for each system.
You dont feed the stock PCM some inputs, you leave it as it was with all the information it normally receives.
You only feed the aftermarket ecu the info it needs to do the jobs you want it to do. As far as the piggyback goes in it's most basic form all you would remove from the stock ecu are 8 injectors and 8 coils. That gives you total control via the standalone over all fuel/spark delivery
Above and beyond that you can of course remove other controls from the OEM ecu whether it's idle, fans, throttle if DBW etc etc. But you do not need to. It's entirely your choice.
Things like boost control, nitrous etc etc are in no way integrated with the OEM ecu anyway so are irrelevant. That's tied only to the aftermarket ecu.
It can be as simple or difficult as you want to make it depend on what controls you want for each system.
Manifold Air Pressure
Throttle Position Switch
Coolant Temperature Sensor
Crank Sensor
Cam Sensor
Idle Air Control
Manifold Air Temperature
What would you suggest to address those getting back into the Holley PCM? I realize true piggy back systems have worked well on C6 Vette stuff(Know a bunch of people doing it) but with the F-body probably some more hackery involved.
During a NYS inspection for example they have you start the car...Does NYS computer look for additional information at that point? PIDs? which is why I was mentioning feeding the stock PCM crank/ect. Obviously injectors/coils are no needed from the stock PCM I figured it would be easier to run the Holley harness and run some additional wires to a handful of pins on the stock computer.
There is a vendor who makes a harness like I just described and sells it for that exact purpose.
Last edited by mshadow; Jan 6, 2016 at 11:27 AM.
9 Second Club
Joined: Nov 2003
Posts: 13,616
Likes: 185
From: Norn Iron
I've already very clearly answered this.
You can easily pair up powered sensors between 2 ecu's, you cannot pair up 2 wire resistive sensors unless the ecu you're using does not have an internal pullup or it can be turned off.
So MAP, TPS, Crank/Cam can all simply be shared between both ecu's. All you'd need to feed into the Holley in this case is the signal wire from each. You would not need to connect 5v and sensor grounds, although it should do no harm to do so.
CTS can be shared if the ecu meets the requirements I mentioned above, otherwise the new ecu will require it's own dedicated CTS, same applies for IAT. No big deal, 2 wires each.
As for idle, as I already said, you can leave idle control with the stock ecu, or you could re-wire this to the new ecu. Doesnt really matter.
If you want to run an idle speed different from what the stock ecu wants, then you'd maybe want the aftermarket ecu to take over this function. But it is not essential
You can easily pair up powered sensors between 2 ecu's, you cannot pair up 2 wire resistive sensors unless the ecu you're using does not have an internal pullup or it can be turned off.
So MAP, TPS, Crank/Cam can all simply be shared between both ecu's. All you'd need to feed into the Holley in this case is the signal wire from each. You would not need to connect 5v and sensor grounds, although it should do no harm to do so.
CTS can be shared if the ecu meets the requirements I mentioned above, otherwise the new ecu will require it's own dedicated CTS, same applies for IAT. No big deal, 2 wires each.
As for idle, as I already said, you can leave idle control with the stock ecu, or you could re-wire this to the new ecu. Doesnt really matter.
If you want to run an idle speed different from what the stock ecu wants, then you'd maybe want the aftermarket ecu to take over this function. But it is not essential
Teching In
Joined: Mar 2016
Posts: 4
Likes: 0
I hate how I get all pumped up for these engines and how powerful and efficient you can make them with doing a few small mods or going all the way
. Then no one can figure out how to make them get passed the governments emissions BS
... Holley states on their page that their system out performs Europes emissions and the US emission standards. Why the eff cant we get this thru the governments head? Their must be some easier way to run a Holley system and daily drive the thing. 
Ive read all the responses here and in order for these aftermarket ECU's to have full potential they need near full control of the engine and accessories. Wiring a few things here and there is no issue but when you start splicing things together = a problem waiting to happen.
Isnt there a few pins on the back of the stock ECU we can run some aluminum foil between and run power to the some bitch and fool the government? Then we could run that Holley ****!
. Then no one can figure out how to make them get passed the governments emissions BS... Holley states on their page that their system out performs Europes emissions and the US emission standards. Why the eff cant we get this thru the governments head? Their must be some easier way to run a Holley system and daily drive the thing. Ive read all the responses here and in order for these aftermarket ECU's to have full potential they need near full control of the engine and accessories. Wiring a few things here and there is no issue but when you start splicing things together = a problem waiting to happen.
Isnt there a few pins on the back of the stock ECU we can run some aluminum foil between and run power to the some bitch and fool the government? Then we could run that Holley ****!
LS1 Tech Stories
The Best V8 Stories One Small Block at Time
Gas Monkey Built a 6-Wheel Ferrari Testarossa With a Corvette LT4 Engine
Verdad Gallardo
7 Most Reliable High-Performance Engines GM Has Ever Built
Verdad Gallardo
Amazing '71 Camaro Restomod Is Modern Muscle Car Under the Skin
Verdad Gallardo
6 Common C5 Corvette Failures and What's Involved In Repairing Them
Pouria Savadkouei
Retro Modern Bandit Pontiac Trans AM Comes With Burt Reynolds' Autograph
Verdad Gallardo
Top 10 Greatest Cadillac V Series Performance Models Ever, Ranked
Pouria Savadkouei
Top 10 Most Powerful Chevy Trucks Ever Made!
Hennessey's New Supercharged Silverado ZR2 Has 700 HP
Verdad Gallardo
Coachbuilt N2A Anteros Is an LS2-Powered C6 Corvette In Italian Clothes
Verdad Gallardo 9 Second Club
Joined: Nov 2003
Posts: 13,616
Likes: 185
From: Norn Iron
I hate how I get all pumped up for these engines and how powerful and efficient you can make them with doing a few small mods or going all the way. Then no one can figure out how to make them get passed the governments emissions BS... Holley states on their page that their system out performs Europes emissions and the US emission standards. Why the eff cant we get this thru the governments head? Their must be some easier way to run a Holley system and daily drive the thing.
Ive read all the responses here and in order for these aftermarket ECU's to have full potential they need near full control of the engine and accessories. Wiring a few things here and there is no issue but when you start splicing things together = a problem waiting to happen.
Isnt there a few pins on the back of the stock ECU we can run some aluminum foil between and run power to the some bitch and fool the government? Then we could run that Holley ****!
. Then no one can figure out how to make them get passed the governments emissions BS... Holley states on their page that their system out performs Europes emissions and the US emission standards. Why the eff cant we get this thru the governments head? Their must be some easier way to run a Holley system and daily drive the thing. Ive read all the responses here and in order for these aftermarket ECU's to have full potential they need near full control of the engine and accessories. Wiring a few things here and there is no issue but when you start splicing things together = a problem waiting to happen.
Isnt there a few pins on the back of the stock ECU we can run some aluminum foil between and run power to the some bitch and fool the government? Then we could run that Holley ****!
And by any standard as a generic ecu, Holley from what I see has virtually no ability to run most emissions control equipment anyway, so would be a poor choice if you wanted to try and build something that meets all EPA and government rules ( and probably few aftermarket ecu's would either...simply because they have no need to accommodate such bullshit )
So do YOU have the ability ( and money/equipment to prove it ) to build and configure an engine/ecu package to meet all the bullshit regulations that governments throw down ?
I suspect not....hell look what happened VW recently.
And some of the Link ecu's offer OBD data and presumably if one scans it will tell you all is well ( or not if there are issues )
Whether of course that scan will be identical to a factory vehicle of same type for purposes of a government test is another matter.
I'm sure I seen another ecu that offered OBD compatibility too, just cant recall which one, but all ecu's should really offer an OBD compliant output as standard. Like really...why not ? Unless there are some legal issues around it given all aftermarket ecu's are pretty much sold "not for street use" and some customers might have unrealistic expectations of it.
Had anyone pulled this off sucsesucclly yet? I thought I had it last year. Made a breakout harness and fed it crank and cam sensor inputs. It was good till I had to start the car then it would get can't communicate error on the inspection computer
Launching!
Joined: Jan 2002
Posts: 299
Likes: 41
From: Detroit, Murder City
Don't hold your breath.
The new inspection stations query the OEM ECU and check to see not only IF the monitors have run, but how often they pass. So the ECU must be able to control the engine enough to execute these monitor and pass with regularity. A standalone ECU in control of fuel, air, and spark does not allow a "piggyback OEM ECU" to execute these intrusive tests and therefore will NOT PASS. It is not simply a matter of having the right wiring harness and connector, guys. The whole point is that the vehicle is running clean enough that the tailpipe emissions are within spec AND the ECU has a history of checking that successfully. No aftermarket standalone ECU does that.
The new inspection stations query the OEM ECU and check to see not only IF the monitors have run, but how often they pass. So the ECU must be able to control the engine enough to execute these monitor and pass with regularity. A standalone ECU in control of fuel, air, and spark does not allow a "piggyback OEM ECU" to execute these intrusive tests and therefore will NOT PASS. It is not simply a matter of having the right wiring harness and connector, guys. The whole point is that the vehicle is running clean enough that the tailpipe emissions are within spec AND the ECU has a history of checking that successfully. No aftermarket standalone ECU does that.
9 Second Club
Joined: Nov 2003
Posts: 13,616
Likes: 185
From: Norn Iron
Don't hold your breath.
The new inspection stations query the OEM ECU and check to see not only IF the monitors have run, but how often they pass. So the ECU must be able to control the engine enough to execute these monitor and pass with regularity. A standalone ECU in control of fuel, air, and spark does not allow a "piggyback OEM ECU" to execute these intrusive tests and therefore will NOT PASS. It is not simply a matter of having the right wiring harness and connector, guys. The whole point is that the vehicle is running clean enough that the tailpipe emissions are within spec AND the ECU has a history of checking that successfully. No aftermarket standalone ECU does that.
The new inspection stations query the OEM ECU and check to see not only IF the monitors have run, but how often they pass. So the ECU must be able to control the engine enough to execute these monitor and pass with regularity. A standalone ECU in control of fuel, air, and spark does not allow a "piggyback OEM ECU" to execute these intrusive tests and therefore will NOT PASS. It is not simply a matter of having the right wiring harness and connector, guys. The whole point is that the vehicle is running clean enough that the tailpipe emissions are within spec AND the ECU has a history of checking that successfully. No aftermarket standalone ECU does that.
I would ck with a NY emissions inspector, see if they can sniff it. Even if it passed it
could fail a visual. Easy to build a second tune, make it lean, for inspection, but its
more than just lean anymore. Somebody out there prob has a conn and input for just
such a thing, lol. In Md they also ck your gas cap, some guys with cells leave the orig.
filler there. Be interesting to see what you come up with.
could fail a visual. Easy to build a second tune, make it lean, for inspection, but its
more than just lean anymore. Somebody out there prob has a conn and input for just
such a thing, lol. In Md they also ck your gas cap, some guys with cells leave the orig.
filler there. Be interesting to see what you come up with.
12 Second Club
Joined: Jan 2003
Posts: 303
Likes: 2
From: Buffalo NY
Don't hold your breath.
The new inspection stations query the OEM ECU and check to see not only IF the monitors have run, but how often they pass. So the ECU must be able to control the engine enough to execute these monitor and pass with regularity. A standalone ECU in control of fuel, air, and spark does not allow a "piggyback OEM ECU" to execute these intrusive tests and therefore will NOT PASS. It is not simply a matter of having the right wiring harness and connector, guys. The whole point is that the vehicle is running clean enough that the tailpipe emissions are within spec AND the ECU has a history of checking that successfully. No aftermarket standalone ECU does that.
The new inspection stations query the OEM ECU and check to see not only IF the monitors have run, but how often they pass. So the ECU must be able to control the engine enough to execute these monitor and pass with regularity. A standalone ECU in control of fuel, air, and spark does not allow a "piggyback OEM ECU" to execute these intrusive tests and therefore will NOT PASS. It is not simply a matter of having the right wiring harness and connector, guys. The whole point is that the vehicle is running clean enough that the tailpipe emissions are within spec AND the ECU has a history of checking that successfully. No aftermarket standalone ECU does that.
People run into the issue above on stuff like the new Coyotes I assume thats why HP tuners now lets you modify the testing parameters for the monitor checks.
There were a couple shops on here who had cars running on Holley split a handful of sensors into the stock PCM and had it pass the OBDII inspections. You're talking about technology thats pre CAN bus and you're talking about PCM technology that is 20+ years old at this point the readiness monitor checks back then were trivial.
The assumption with original posters car is once you turn the car to run the inspection computer pulls data from a handful of sensors and just throws a generic error when it doesn't see input from them. You could pretty easily throw a OBDII splitter on and log the requests the inspection computer makes and deal with it from that route see what you're missing or the process.
