LS1 Miata - PCM & Harness help needed!
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LS1 Miata - PCM & Harness help needed! I put an 04 GTO LS1 in my 2000 Miata. The harness & PCM are out of the GTO. The PCM has been re-programmed to accomodate the swap. I hooked up the PCM, cranked the motor, but it doesn't start.
Here's what I know:
-Pinout #20 & #57 have 12v battery power
-Pinout #19 has 12v ignition power
-when key is in run position - fuel pump runs - fuel is reaching fuel rail
-no spark at spark plugs
-I can't communicate with PCM with scanner - get error message
(serial data line is Blue connector #58 - checked & verified)
-I unplugged the MAF to see if it would start - no luck
Questions:
-where and how much voltage should I see at the coils?
-is there a commion wire or pinout which supplies power to the coils?
-any ideas?
*suspect the PCM, but I might have overlooked something when I re-did the harness
Any help would be appreciate. Thanks, Ray
Here's what I know:
-Pinout #20 & #57 have 12v battery power
-Pinout #19 has 12v ignition power
-when key is in run position - fuel pump runs - fuel is reaching fuel rail
-no spark at spark plugs
-I can't communicate with PCM with scanner - get error message
(serial data line is Blue connector #58 - checked & verified)
-I unplugged the MAF to see if it would start - no luck
Questions:
-where and how much voltage should I see at the coils?
-is there a commion wire or pinout which supplies power to the coils?
-any ideas?
*suspect the PCM, but I might have overlooked something when I re-did the harness
Any help would be appreciate. Thanks, Ray
Staging Lane
Joined: Oct 2006
Posts: 62
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Hi, on the GTO the coils were powered via a plug (C101) pin 2, red wire was for the even coils and pin 3 light green wire was for the odd coils. These wires went via 2 15amp fuses to the battery. If you no longer have those plugs you can trace the wires back from the coil plugs.
The wire you need for the OBD2 connector is from pcm plug C1 (blue) pin 58 which is the RFA class 2 serial data. Which by the way can be found on the GTO plug C206 pin 26yellow wire.
Hope that helps.
The wire you need for the OBD2 connector is from pcm plug C1 (blue) pin 58 which is the RFA class 2 serial data. Which by the way can be found on the GTO plug C206 pin 26yellow wire.
Hope that helps.
Staging Lane
Joined: Oct 2006
Posts: 62
Likes: 0
The PCM pins 20 and 57 on the blue connector were also hot all the time but pin 19 was via ignition.
Thread Starter
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I connected power this moring to the coils. I have spark when engine cranks, but no fuel. The fuel pump does run, there is fuel at the rail. I went and put a little gas in the manifold, cranked the engine and it came to life! Looks like I missed another wire or two. Do you have any ideas?
Thanks again
Thanks again
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Verdad Gallardo I don't know specifically about the GTO PCM, but an FBody LS1 PCM & associated electronics require 3 specific grounds. Usually, when you can't communicate w/ the PCM & there is an injector pulse or spark issue, a ground is the culprit. Will see what I can find schematic wise.
Staging Lane
Joined: Oct 2006
Posts: 62
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Hi, the grounds for the coils are all black/red and would have been on connector C101 pin 5. Once again if you no longer have that connector trace the black/reds back from the coil plugs.
The other ground you need is connector C206 pin 2 (black) Also make sure you have good grounds from your engine block to the chassis (i.e. from each shock tower to the heads). Grounding the pcm case wouldn’t hurt either.
If you still have problems check that VATS has been disabled.
Anything else just ask.
edit
Re no fuel, if the pcm sees the engine crank but not start it will shut off fuel after around 2 seconds.
The other ground you need is connector C206 pin 2 (black) Also make sure you have good grounds from your engine block to the chassis (i.e. from each shock tower to the heads). Grounding the pcm case wouldn’t hurt either.
If you still have problems check that VATS has been disabled.
Anything else just ask.
edit
Re no fuel, if the pcm sees the engine crank but not start it will shut off fuel after around 2 seconds.
Last edited by RHDV8; May 14, 2009 at 03:21 PM.
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I appreciate the info. I don't have either C101 or C206 harness connectors. The wires are in the main harness. The block & heads are grounded to the frame, which is the ground for the car.
Can I assume the PCM supplies a voltage signal to each injector?
Also, what does C206 ground?
The VATS has been disabled.
Thanks again!
Can I assume the PCM supplies a voltage signal to each injector?
Also, what does C206 ground?
The VATS has been disabled.
Thanks again!
It's my understanding that those are 12VDC, not grounds. The PCM switches each injector's ground when it pulses it, separate driver for each injector.
Staging Lane
Joined: Oct 2006
Posts: 62
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The red/blacks are ground, The pcm trigger/signal wires are from the green pcm plug, pins, 26,27,28, 29, 66, 67, 68, and 69 (various colours). The reds and light greens (depending on even or odd coils) are +12V direct from the battery and the brown and purple are the low reference wires from the green pcm plug pins 60 and 61. Apart from the spark plug wires that’s it.
Sorry, cant help with what that specific black earth wire does but it is bundled within the loom to other earths. If you found the other wires from the old C206 plug the black should be in the same place if that helps?
The injector wiring is, hang on a min...........
Right, injectors have but 2 wires, one +12V (red for bank 2 and light green for bank 1) from the same place as the red and light green for the coils as in previous post.
And a fuel injection control wire (multi colours) from the pcm blue connector pins 4, 44, 37, 77, 36, 3, 76, and 43
Last edited by RHDV8; May 14, 2009 at 03:35 PM.
If you can peel yourself away from the driver's seat now that it's running right, that is!
Can you provide the ECM pinouts you used and any information that may help another swapper of this specific setup.
Very importantly, Did you have the ECM reprogrammed for the swap, what did you have removed?
I'm glad you found your problem. For others that do a search on this problem, I had a similar problem with my LS1. We had fuel at the rail, but no injector pulse. We actually forgot to plug in the crank sensor behind the starter. We then experienced an extended cranking before it started. It would start and then run just fine, but the extended start had us puzzled. We thought we were losing fuel pressure at the rail and were having to prime it each time we tried to start. Turns out we had a broken wire at the cam sensor so the PCM was relying on just the crank signal only and compensating, which takes longer to start. fixed the problem and it now starts right up each and every time.
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Ray,
Where do you live? I'm finishing up my wiring with an '04 GTO harness and PCM which was reprogrammed to remove VATS among some other things. Hopefully I'll get it cranked over this weekend. This is going into an '01 Miata with a freshly rebuilt LS6 out of an '02 Z06.
Rotor vs Piston, I have the pinouts for the '04 GTO harness in a text file. PM me your email.
Frank
Where do you live? I'm finishing up my wiring with an '04 GTO harness and PCM which was reprogrammed to remove VATS among some other things. Hopefully I'll get it cranked over this weekend. This is going into an '01 Miata with a freshly rebuilt LS6 out of an '02 Z06.
Rotor vs Piston, I have the pinouts for the '04 GTO harness in a text file. PM me your email.
Frank