LS1 Wiring PCM to Fuse Box
08-29-2023, 10:41 AM
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Car: 1988 Camaro (Base model)
Engine: 99 LS1
Transmission: 99 4L60E
LS1 Wiring PCM to Fuse Box
We pulled the v6 drivetrain from our 88 Camaro and installed an LS1/4L60E from a 99 Firebird off of Hawks Motorsports.
We have the wiring harness and PCM from the LS1 drivetrain.
We are having a tough time figuring out how it ties into the fuse box and dash.
Do we need a BCM, since we don't have one, from the firebird to make the dash/lights work?
If no, then how do we run the Dash/lights?
We have seen images of the 99 Firebird and it appears to have 3 fuse boxes.
How does the PCM connect to a fuse box without having to rewire the harness?
We have seen others rewire their harness to incorporate a new fuse box, but we cannot wrap our heads around why they don't reuse the fuse box from the 4th gen F-bodies.
We have also seen that the stock 4th gen F-body fuse box has a pin labeled PCM power, so we know that the PCM was originally connected to that fuse box. However, none of our research has been able to tell us how.
We have the wiring harness and PCM from the LS1 drivetrain.
We are having a tough time figuring out how it ties into the fuse box and dash.
Do we need a BCM, since we don't have one, from the firebird to make the dash/lights work?
If no, then how do we run the Dash/lights?
We have seen images of the 99 Firebird and it appears to have 3 fuse boxes.
How does the PCM connect to a fuse box without having to rewire the harness?
We have seen others rewire their harness to incorporate a new fuse box, but we cannot wrap our heads around why they don't reuse the fuse box from the 4th gen F-bodies.
We have also seen that the stock 4th gen F-body fuse box has a pin labeled PCM power, so we know that the PCM was originally connected to that fuse box. However, none of our research has been able to tell us how.
08-29-2023, 12:31 PM
#2
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Car: '90 RS
Engine: 377 LSX
Transmission: Magnum T56
Re: LS1 Wiring PCM to Fuse Box
Your dash lights, and headlights for the matter run off a separate harness than the engine one. Your stock C100 has two main harness connections, both going through the stock fuse block. You don't see folks swap the 4th gen fuse blocks because 90% of what you still need resides in the stock box. You'll need to splice the 4th gen engine harness into the 3rd gen system. I'd strip out anything you won't reuse from the 4th gen harness. There is more to this and I am just clearing a few things up.
Take a look at this thread along with all the stickies at the top of this forum.
https://www.thirdgen.org/forums/ltx-...rt-finish.html
Everything you need is in this thread.
Take a look at this thread along with all the stickies at the top of this forum.
https://www.thirdgen.org/forums/ltx-...rt-finish.html
Everything you need is in this thread.
08-29-2023, 02:44 PM
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Car: '89 Firebird
Engine: 7.0L
Transmission: T56
Re: LS1 Wiring PCM to Fuse Box
If you're looking for a way to run as much as you can off the stock 3rd gen fuse panel, then the link Shifty provided is where you begin. If you want to add your own underhood power center instead then you can do that too (that's what a lot of people do).
As far as powering all the stock chassis stuff (lights, HVAC, dash etc...), all you need to do is locate Fusible Link 'A' and 'B' in the mess of wiring in your engine bay and give that power and your whole stock fuse panel (under dash) will power up. Those are both Red wires, 12 gauge in size.
I'm not going to lie to you, wiring is the the most difficult part of the swap job.
Last edited by QwkTrip; 08-29-2023 at 02:58 PM.
09-03-2023, 05:31 PM
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Car: 1988 Camaro (Base model)
Engine: 99 LS1
Transmission: 99 4L60E
Re: LS1 Wiring PCM to Fuse Box
Knowing that we need to splice the 3rd gen harness to the 4th gen is a massive help. However, we are running into related issues. I have attached all of my findings and notes that are related to my questions to hopefully help understand the questions.
We noticed that in the '87 connector C207 the fuel pump relay is located in pin D, but in the '88 pin D is a fan and the entire C207 has no fuel pin at all. Are we missing it or is it located somewhere else, if so, then where?
We noticed that the '87 connector C207 pin K is a VSS buffer to the ECM, but the '88 pin K is just an ECM buffer. I remember reading (Pocket's LS1 wiring guide) that pin K in the '87 was connected to R50 in the LS1 ECM, can we do the same in our '88?
What do we do with C207 pin N? Does it go to B32 and B34, or just one of them, if so which one?
Are the any wires in our '88 C221 connector that we need to rewire for the LS1 ECM?
I read that VATS needs to be disabled in this swap but didn't understand why. Could we get more explanation?
On the '88 C100, what is the difference between E6 and G4? How do they connect to the LS1 ECM and what do they connect to? R9, R30, or something else?
Is there a more detailed description of what each pin does for the '88 C207 connector, what we have is extremely simplified?
Any help is much appreciated.
We noticed that in the '87 connector C207 the fuel pump relay is located in pin D, but in the '88 pin D is a fan and the entire C207 has no fuel pin at all. Are we missing it or is it located somewhere else, if so, then where?
We noticed that the '87 connector C207 pin K is a VSS buffer to the ECM, but the '88 pin K is just an ECM buffer. I remember reading (Pocket's LS1 wiring guide) that pin K in the '87 was connected to R50 in the LS1 ECM, can we do the same in our '88?
What do we do with C207 pin N? Does it go to B32 and B34, or just one of them, if so which one?
Are the any wires in our '88 C221 connector that we need to rewire for the LS1 ECM?
I read that VATS needs to be disabled in this swap but didn't understand why. Could we get more explanation?
On the '88 C100, what is the difference between E6 and G4? How do they connect to the LS1 ECM and what do they connect to? R9, R30, or something else?
Is there a more detailed description of what each pin does for the '88 C207 connector, what we have is extremely simplified?
Any help is much appreciated.
09-04-2023, 02:08 PM
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Re: LS1 Wiring PCM to Fuse Box
Pocket recently shared wiring diagrams he made during the days when he built harnesses. I don't know if it will help you or not, but I see it has some C207 and C221 info.
https://www.thirdgen.org/forums/ltx-...-diagrams.html
https://www.thirdgen.org/forums/ltx-...-diagrams.html
09-04-2023, 02:15 PM
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Car: '89 Firebird
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Re: LS1 Wiring PCM to Fuse Box
The full list of Pocket's how-to threads is listed in Post #1 of this thread,
https://www.thirdgen.org/forums/ltx-...lectrical.html
Sorry I'm not of more help, I am more familiar with Holley EFI than I am with GM PCM swaps. But maybe one of those threads will have the golden nugget you're looking for.
https://www.thirdgen.org/forums/ltx-...lectrical.html
Sorry I'm not of more help, I am more familiar with Holley EFI than I am with GM PCM swaps. But maybe one of those threads will have the golden nugget you're looking for.
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09-06-2023, 09:28 AM
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Car: 92 Firebird
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Axle/Gears: 8.8 3.73
Re: LS1 Wiring PCM to Fuse Box
Knowing that we need to splice the 3rd gen harness to the 4th gen is a massive help. However, we are running into related issues. I have attached all of my findings and notes that are related to my questions to hopefully help understand the questions.
We noticed that in the '87 connector C207 the fuel pump relay is located in pin D, but in the '88 pin D is a fan and the entire C207 has no fuel pin at all. Are we missing it or is it located somewhere else, if so, then where?
Pin D C207 is for 85-87 EFI cars. 88-89 Will use C100 G4
We noticed that the '87 connector C207 pin K is a VSS buffer to the ECM, but the '88 pin K is just an ECM buffer. I remember reading (Pocket's LS1 wiring guide) that pin K in the '87 was connected to R50 in the LS1 ECM, can we do the same in our '88?
Since there is no direct wire from the ECU to electric speedos, the buffer box circuit is recycled. C207 pin K goes from the C207 to the buffer box. Jumper pins C&F on the box to allow a strait shot from the C207 to the speedo. Unfortunately, your 88 camaro will have a mechanical speedo, so none of this is relevant. You'll need either a mechanical driver box or to switch to an aftermarket electric gauge
What do we do with C207 pin N? Does it go to B32 and B34, or just one of them, if so which one?
P/Neutral goes from the shifter to the ECU on auto cars. It is an optional circuit to bump idle when in park/n. B32 for 0411 PCMs. Years past, info on the circuit was sparse, so using both pins was the norm. B34 doesn't do anything without a manual tune in the ECU
Are the any wires in our '88 C221 connector that we need to rewire for the LS1 ECM?
88 Should not have a C221
I read that VATS needs to be disabled in this swap but didn't understand why. Could we get more explanation?
It's a checkbox in the ECU tune
On the '88 C100, what is the difference between E6 and G4? How do they connect to the LS1 ECM and what do they connect to? R9, R30, or something else?
G4 is the fuel pump + feed. E6 was a relay override, often called the price connector. It went to the old ALDL under the column
Is there a more detailed description of what each pin does for the '88 C207 connector, what we have is extremely simplified?
Qwiktrip posted a link to exactly that
Any help is much appreciated.
We noticed that in the '87 connector C207 the fuel pump relay is located in pin D, but in the '88 pin D is a fan and the entire C207 has no fuel pin at all. Are we missing it or is it located somewhere else, if so, then where?
Pin D C207 is for 85-87 EFI cars. 88-89 Will use C100 G4
We noticed that the '87 connector C207 pin K is a VSS buffer to the ECM, but the '88 pin K is just an ECM buffer. I remember reading (Pocket's LS1 wiring guide) that pin K in the '87 was connected to R50 in the LS1 ECM, can we do the same in our '88?
Since there is no direct wire from the ECU to electric speedos, the buffer box circuit is recycled. C207 pin K goes from the C207 to the buffer box. Jumper pins C&F on the box to allow a strait shot from the C207 to the speedo. Unfortunately, your 88 camaro will have a mechanical speedo, so none of this is relevant. You'll need either a mechanical driver box or to switch to an aftermarket electric gauge
What do we do with C207 pin N? Does it go to B32 and B34, or just one of them, if so which one?
P/Neutral goes from the shifter to the ECU on auto cars. It is an optional circuit to bump idle when in park/n. B32 for 0411 PCMs. Years past, info on the circuit was sparse, so using both pins was the norm. B34 doesn't do anything without a manual tune in the ECU
Are the any wires in our '88 C221 connector that we need to rewire for the LS1 ECM?
88 Should not have a C221
I read that VATS needs to be disabled in this swap but didn't understand why. Could we get more explanation?
It's a checkbox in the ECU tune
On the '88 C100, what is the difference between E6 and G4? How do they connect to the LS1 ECM and what do they connect to? R9, R30, or something else?
G4 is the fuel pump + feed. E6 was a relay override, often called the price connector. It went to the old ALDL under the column
Is there a more detailed description of what each pin does for the '88 C207 connector, what we have is extremely simplified?
Qwiktrip posted a link to exactly that
Any help is much appreciated.
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