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Old 05-01-2010, 03:43 PM   #1
rentfrow1
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Default 99 SL2 PCM Swap (Auto to 5spd)

I recently swapped out the automatic transmission in my 99 SL2 for a manual (also did the 5th gear swap), and it works great other than having the SES light on. Now, I am trying to replace the PCM with one from an SL2 with a manual to cure the SES light. I got one in now, and the engine seems to run just as well, or better, but I have the service wrench light on now, and the fuel gauge doesn't give a reading. Anyone have any ideas? I am wondering if it has something to do with the CPS relearn.

Details:
Before connecting the new (junkyard) PCM, I had to cut some of the tabs off of the connectors so that they would plug in. When I first connected the new PCM from a 99 SL2, the engine started and ran rough for a few seconds while the PCM and engine got to know each other. I cycled the ignition, and it fired right up, but I noticed the fuel gauge wasn't working, and the low fuel light was on. After the engine ran for 30 seconds, or so, the service wrench light came on. Now when I start the engine, the fuel gauge never moves, but the service wrench light only comes on after the engine runs for a little while. Also, everything still works the same with the original PCM, so I probably didn't break anything. Also, there is no difference if the 4th connector, that goes to the automatic transmission is connected or not.
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Old 05-01-2010, 05:46 PM   #2
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Default Re: 99 SL2 PCM Swap (Auto to 5spd)

just a heads up - cruise may not work in 5th gear with the manual pcm, since it's not the original gear ratio.
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Old 05-01-2010, 06:03 PM   #3
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Default Re: 99 SL2 PCM Swap (Auto to 5spd)

I forgot to mention, when I scanned the new PCM for codes, the cheap scanner at OReilley said there were no error codes and that all of the emissions tests were passed except the heated O2, b/c I had only driven it a few miles.

I also went back to the junkyard to look at the donor car more closely. The critical things do match:
  • DOHC
  • Manual
  • w/ AC
  • w/o Cruise Control
  • w/o ABS
  • Also, both are power nothing (windows, locks)
The differences I found were:
  • It has the normal valve train, mine has the roller-rocker setup.
  • My washer fluid reservoir has the cut-out where the air pump would go.
  • The exhaust manifold is different. I have not seen any cars with the manifold like mine.
  • The PCV is a little different. Mine has the plastic elbow on the PCV itself.
  • It had the analog odometer, mine is digital.
Basically my car looks a lot like a 2000 under the hood, and I have no idea why. I am guessing my car was produced toward the end of the model year, and they put the newer powertrain in it.
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Old 05-01-2010, 06:05 PM   #4
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Default Re: 99 SL2 PCM Swap (Auto to 5spd)

Quote:
Originally Posted by PurdueGuy View Post
just a heads up - cruise may not work in 5th gear with the manual pcm, since it's not the original gear ratio.
I know, but I don't have cruise anyway. Also, I already did the swap along with an engine rebuild in January. I have put about 5000 miles on it since then.
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Old 05-02-2010, 12:43 AM   #5
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Default Re: 99 SL2 PCM Swap (Auto to 5spd)

Quote:
Originally Posted by rentfrow1 View Post
[*]It had the analog odometer, mine is digital.[/LIST]
The donor car is a '96 or '97. It also has a completely different fuel system, and it's a surprise that PCM runs your engine at all.
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Old 05-02-2010, 01:48 AM   #6
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Default Re: 99 SL2 PCM Swap (Auto to 5spd)

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Originally Posted by madpogue View Post
The donor car is a '96 or '97. It also has a completely different fuel system, and it's a surprise that PCM runs your engine at all.
Some very early '98s have been reported with analog odometers, but true enough that most '98s are digital.
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Old 05-02-2010, 03:39 PM   #7
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Default Re: 99 SL2 PCM Swap (Auto to 5spd)

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Originally Posted by madpogue View Post
The donor car is a '96 or '97. It also has a completely different fuel system, and it's a surprise that PCM runs your engine at all.
I checked the VIN. Both potential donor cars were '99.
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Old 05-02-2010, 07:52 PM   #8
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Default Re: 99 SL2 PCM Swap (Auto to 5spd)

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Originally Posted by rentfrow1 View Post
I checked the VIN. Both potential donor cars were '99.
Then the analog odometer is a transplant (in the donor), and one has to wonder what else might be. Any chance you can still get a look at the options decal on the spare tire cover of the donor car? That might be more conclusive as to compatibility of the PCM.
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Old 05-02-2010, 08:10 PM   #9
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Default Re: 99 SL2 PCM Swap (Auto to 5spd)

Whats a 5th gear swap?

EDIT: Also, isnt Richpin's SL2 a 98'? Im pretty sure he has an analog odometer as well, as seen in a few of his videos.
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Old 05-02-2010, 08:45 PM   #10
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Default Re: 99 SL2 PCM Swap (Auto to 5spd)

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Whats a 5th gear swap?
Open the end cover, remove the 5th-speed gears and install the 5th-speed gears from an MP2 (SOHC) tranny. Results in lower engine RPM cruising at highway speed. '96-'02 cars lose cruise control, however, since the PCM doesn't detect an "expected" gear/speed ratio, and assumes you're pressing the clutch (PCM "software" clutch switch replaces the actual two-dollar switch on the pedal arm).

Quote:
EDIT: Also, isnt Richpin's SL2 a 98'? Im pretty sure he has an analog odometer as well, as seen in a few of his videos.
As said, it's possible some early '98s had analog odometers, but there's no way a '99 would have an analog from the factory. The donor car was hacked, and may have otherwise been hacked, and this _might_ be what's behind the "Wrench" light.
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Old 05-02-2010, 10:18 PM   #11
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Default Re: 99 SL2 PCM Swap (Auto to 5spd)

I will double check, but there were 4 '99 SL's at the junkyard, and I think all of them had analog odometers.

Anyway, the point is that my car has a slightly different engine than the ones at the junkyard. Does that mean that I cannot use the new PCM without getting it reprogrammed, and for that matter will I ever be able to find a PCM that will work with my car without being reprogrammed? If I can't eliminate the need to reprogram the PCM, then I will just suck it up and go to a dealer with the PCM I have. The thing I am really concerned about is the gas gauge not working with the new PCM.

I have been driving with the PCM for the automatic since January (and checking the junkyard for new cars the entire time), and it is fine, but I would like to get rid of the SES light. Also, it seems like the manual PCM controls the throttle better when I push the clutch to change gears or coast. It drops the RPM faster which makes it easier to match the revs for the next gear. With the automatic PCM, the RPM floats around or flares when I push the clutch. Also, when I coast it holds the RPM at 1500 to 1800 until I stop.
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Old 05-05-2010, 12:09 AM   #12
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Default Re: 99 SL2 PCM Swap (Auto to 5spd)

Update:

I went back to the junkyard and double checked the car that I got the computer off of, and it turns out I got it mixed up with another sl. It was a '96. I got a different PCM from an actual '99, and it works great, but I still have the service wrench light on. I am pretty sure it is because the car I got the computer off of had cruise control, and mine doesn't (best I could do). They had 4 99's. Two were automatic and the other already had the computer pulled out.

To get rid of the service wrench light can I jump a wire in the cruise connector, or would it be easier to just connect a cruise module? I cannot use cruise with the 5th gear swap, so functionality doesn't matter. Also, would it work just with the cruise module connected, or would I have to do something to the connector for the switch module in the steering wheel?

Sorry about the wild goose chase.
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