'96 DOHC with '91-'93 wiring harness

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Linlor
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Joined: Sun Oct 29, 2017 6:11 pm

'96 DOHC with '91-'93 wiring harness

Post by Linlor »

All;

Thanks for your previous help and support on my wandering toward a wiring conclusion. I have gone out and looked for a '96/'97 wiring harness I can start with for OBDII but I am coming up dry right now.

With the target of getting this car back on the road some day soon, I have opted to put the '91-'93 wiring harness I already have in to the project to get it running. I will go back to do the OBDII later once I break everything in a bit.

In that light, I have a few questions about putting the '91-'93 harness on to a '96 engine....

Questions:
1. I have traced all my sensors through the harness to confirm I am correct in my sensor guesses. I have everything connected except for a couple sensors.
a. I have a two pin sensor connector that I am not sure about. I think it might be for the coolant low level sensor but I don't know where that would be on a '96 engine
b. The other option it might be is the mat sensor connector? The sensor that sits in the intake tube from air cleaner to throttle body.
c. I have seen reference to these but I have not actually seen any pictures of them?
d. Is that senor handled in a different manner on the '96 engine?

2. Does the alternator power wire go to the electrical block on the passenger fender well below the C500 block or does it wrap around to the power connector on the starter?
a. I know the main battery power connects down to the starter as well in the Fiero but I plan to make a connector station in the passenger fender well where both my power and ground from the battery up front connects and then distributes from there so I could just run the alternator wire over to that connector rather than to the starter?

3. MAP sensor
a. I see reference to the MAP sensor on '91-'93 engines and the '96 engine uses MAF on the throttle body.
b. Do I need to wire up a MAP sensor on the '96 and if so, where as I don't have any sensor wires left to connect to something like that???

I think that should do it for now but I am sure I will be back asking more questions soon.

Thanks
Don
Linlor
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Joined: Sun Oct 29, 2017 6:11 pm

Re: '96 DOHC with '91-'93 wiring harness

Post by Linlor »

I found most of the wiring questions except for one plug that I think is the MAT sensor that goes into the intake tube. Plug looks right from the pics of the sensor I saw at the parts store anyway. Going with that until proven otherwise.

I don't see any plugs for a MAP sensor in my conversion wiring harness so I will need to go back to the wiring bundle and trace wires until I see where it ends up I guess.

Next question is the evap canister. Do you guys use the old Fiero canister or swap in the 3.4 canister as it looks like it is a bit bigger. Also, I have the tube from the gas tank but where do the tubes go back on to the engine on the 3.4? The Fiero was up front of the engine but it has been so long since I tore out all the engine bay that I am not sure where pieces go back in anymore.....

Thanks for any help you might be able to provide.
Don
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Shaun41178(2)
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Re: '96 DOHC with '91-'93 wiring harness

Post by Shaun41178(2) »

You might have to use the evap can from the donor car. The fiero evap had no sensor. If the donor uses no aensor than using the fiero Eva will be fine. Its just some vacuum connections.

There is a vent line on the fuel tank that went to the evap can. Hook that back up or leave it open.
FieroPhrek working on that ls4 swap for 18 years and counting now. 18 years!!!!! LOL

530 whp is greater than 312
FieroWanaBe1
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Re: '96 DOHC with '91-'93 wiring harness

Post by FieroWanaBe1 »

MAP on the 96 engine is on the Throttle body ARM that connects the throttle body to the Upper intake Plenum/Runners.

It is physically different than the one used on the OBD1 ('91-'93) engines. I do not know if they are compatible electronically, and they do not physically interchange, so you may have to use an early GM 1 Bar MAP and remotely plumb it.

An easy way to identify them is to go to rock auto and look at the part pictures for the specific year engine, provided they catalog them accurately the differences will be clear.
car.
Linlor
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Re: '96 DOHC with '91-'93 wiring harness

Post by Linlor »

Thanks for the help folks.

I think
I am close...... :-D

I ended up having a problem with the alternator. I have the '96 engine of course so the harness was set up with a '91-'93 harness set up for a '94-'95 engine that I had started with. I am now working out the alternator. I ended up needing a '96 alternator so needed the new pigtail mapped into the older harness.

My latest question.

I have the pigtail sorted I think but have a question. The red #1 wire still goes to the inline fused power feed and I believe I have the third wire identified as the feed to C500 B3 which goes to the dash charging light. In the '96 wiring harness, there is a supplied power feed on the 4th pin.

Is this a required power feed to the alternator? the older alts don't have it. The 3rd pin of the '96 wiring harness goes to the pcm vs the older going to a powered charge light in the Fiero through B3.

Hope someone has some feedback as I think that is my last question to get the wiring harness buttoned up.

Thanks
Don
Linlor
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Re: '96 DOHC with '91-'93 wiring harness

Post by Linlor »

Good evening all;

I have not been over here in quite a while. I had a member over on the other board mention that there was this board available to possibly help with some issues I have encountered in my build. Way back in 2017, I thought I was close to being done with the build and needed a few more items and sensors figured out and I was ready to go. Well, I figured out the last of the sensors, but I am embarrassed to say I m just getting to starting the car now. Life happens while you coming up with a plan. Anyway.

I have a scenario to present to you for some suggestions and help if anyone is willing.

1. I have finished all wiring and plumbing of fluids around the car and I am now on to the first startup of my crate 96 DOHC with the 91-93 ECM
2. When I originally had my harness built, I would say mid 2000's?...., I had a 94 or 95 engine I was going to rebuild as the donour. I had since found the 96 crate engine so sold off the 95.
3. I still had the harness and did not think of the differences between a 94/95 compared to a 96 donour harness until I am trying to start the engine.
4. My issue is that the wiring from the ecm going to the harness coming off the engine, of course, does not line up at all for the injectors. 96 are sequential and 91-93 is group firing. So I am at the current spot:
- I have three plugs coming off the 96 engine trying to go to 2 plugs coming from the ecm
- I have 6 separate injector control wires that need to be fed from 2 single fire wires.
- I have other wires coming off the top engine harness for MAP, EGR, cam sensor etc. that also need mapping and figuring where in the 91-93 ecm they need to go
5. My idea is to map the three plugs from the engine so I have a common starting point. Map the wires coming into the two plugs from the ecm and wiring harness so I have a good understanding of both sides of the connection points
6. Once I have that, I can then confirm which wires on the engine harness I need to join together to have all injectors single fire using the D3,D9 from the ecm
7. Map the remainder of the wires to mate up with the appropriate wires coming from the main harness to provide signals from the remainder of the sensors.

Does anyone have the 96 top engine harness plugs already mapped out and wiling to provide me with it? Does anyone have a full mapping of a 91-93 ecm into a 96 donour and be wiling to provide me with it?

Is there anything else I need to look into in the wiring harness given it is a 94/95 harness going to a 96 engine? I hope the only differences I will see are the top engine harness plugs but I just don't know at this point.

Any help would be greatly appreciated.
Don
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Re: '96 DOHC with '91-'93 wiring harness

Post by The Dark Side of Will »

Regarding injector wiring: The engine's firing order is 1-2-3-4-5-6. I prefer to alternate injectors on injector fuses... that is wire one fuse to 1, 3 & 5, the other to 2, 4 & 6.

If the OBDI ECM only has two injector drivers, the same logic applies to the ECM as the fuse box. In batch fire, there isn't really any difference in how the injectors are wired, as long as each fuse only supplies half and each driver only sinks half. Heck, you could fuse them 1,3,5 & 2,4,6 and drive them 1,2,3 & 4,5,6 and it wouldn't matter much.

Do you have a factory service manual for either application? You could also get the wiring info from an AllData subscription, which is cheaper than a factory manual.
Linlor
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Re: '96 DOHC with '91-'93 wiring harness

Post by Linlor »

Great feedback and thanks. Currently, the D3 and D9 both go to one pin in the harness I have so I will definitely do what you recommend on the injectors. I will go out tonight and map the plugs for all the top of the engine wiring harness so I know where everything goes as a starting point.

My setup did an EGR delete back when I had the chip flashed the first time but I actually have one installed anyway. I plan to plug the connector in on to the EGR but blank the tube and EGR sides with the EGR installed. I saw through other reading that the EGR is very hard to sort out.

Thanks again for the info and will post drawings of the plugs on the 96 engine for others in the future.

Cheers
Don
FieroWanaBe1
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Re: '96 DOHC with '91-'93 wiring harness

Post by FieroWanaBe1 »

If I remember correctly the EGR on the 96 differs from pre OBD2 engines?
I wired a 96 with a 94 harness 12 years ago.
unfortunately not all my files for the connector diagrams have survived.
These should tell you most of what you need.
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car.
Linlor
Posts: 11
Joined: Sun Oct 29, 2017 6:11 pm

Re: '96 DOHC with '91-'93 wiring harness

Post by Linlor »

Wow thanks very much Fierowannabe. I will use these to figure out the EGR setup. Again, thanks.

My current status of the wiring and troubleshooting. I believe I have everything wired correctly but I am still not getting the injectors to fire.
I have confirmed the pink wire going to the injectors has 12V in run. I have confirmed that when putting power and ground to the injectors, they will fire. The three I can get to anyway. I just don't seem to have the signal coming from D3 and D9 on the 91-93 ECM.

I have ordered an ALDL connector and hopefully it gets here soon. I tried shorting out the A and B terminals on the ALDL with a troubleshooting light but no lights or codes showed. Not saying there are no codes, just didn't come through with the trouble light.

One point I found in the troubleshooting was B10 in the ECM diagrams says power at all times but I don't get power on B10 until I put into Run?

Are there other sensors or triggers inside the 91-93 that I need to check out so I can get power to the injectors?
Linlor
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Re: '96 DOHC with '91-'93 wiring harness

Post by Linlor »

Also one more question as I was guessing but I assumed the ECM A plug starts at the left side and B-D are over to the right? I checked a couple sensors to confirm where they came out from the ECM but I have searched and never actually seen which plugs are which. All makes sense from what I have been tracing but you just don't know.....

Thanks
Don
Linlor
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Re: '96 DOHC with '91-'93 wiring harness

Post by Linlor »

OK so it just keeps getting funnier in a sad way.....

After 15 years, I open up the ECM and low and behold..... no chip. Really, no chip.... So, that REALLY explains a lot about my issues... :twisted:

On the hunt for a new ECM and/or chip. Think I found one in Eastern Canada so I can then ship down to Ryan at Sinister to get programmed. Just keeps getting better.....

I hope the next time I post I will be saying it runs and I can close this chapter of my build and life off....

Thanks for all the help folks.
Don
ericjon262
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Re: '96 DOHC with '91-'93 wiring harness

Post by ericjon262 »

Linlor wrote: Sun Feb 02, 2020 3:59 pm OK so it just keeps getting funnier in a sad way.....

After 15 years, I open up the ECM and low and behold..... no chip. Really, no chip.... So, that REALLY explains a lot about my issues... :twisted:

On the hunt for a new ECM and/or chip. Think I found one in Eastern Canada so I can then ship down to Ryan at Sinister to get programmed. Just keeps getting better.....

I hope the next time I post I will be saying it runs and I can close this chapter of my build and life off....

Thanks for all the help folks.
Don
Lol, at least you have one of the "ah ha" indications of a problem! ever get it back together?
"I am not what you so glibly call to be a civilized man. I have broken with society for reasons which I alone am able to appreciate. I am therefore not subject to it's stupid laws, and I ask you to never allude to them in my presence again."
Linlor
Posts: 11
Joined: Sun Oct 29, 2017 6:11 pm

Re: '96 DOHC with '91-'93 wiring harness

Post by Linlor »

Hey ericjon;

I am waiting for my new chip from Ryan at Sinister. It is in the mail. Ryan doesn't ship to Canada so I had to get it sent to a buddy in NY state and then he shipped it on to me. In transit so should be here any day.
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