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#1059519 - 10/21/18 05:11 AM Functional SES after LS swap  
Joined: Nov 2008
Posts: 622
jmireles Offline
10+ Year
jmireles  Offline
10+ Year
Member

Joined: Nov 2008
Posts: 622
El Paso, Tx
Until today, I hadn't connected the MIL wire to the Monte's SES circuit. I check the 411 PCM every now and then to check for codes but the only one that appears is for the MIL circuit. I want to make the SES light functional. Unless mistaken, the computer provides the ground for the circuit to complete and the SES light on the dash turns on, correct? I used the yellow wire under the dash (old ALDL port). I checked first by grounding the wire and the SES light came on. I connected the 411 PCM MIL wire to the yellow but nothing happens when you turn on the ignition. What am I doing wrong?

Any help is appreciated.

Last edited by jmireles; 10/21/18 05:12 AM.

-'87 Monte SS LS 2/4L65e Quick Perf. 9" w/disk brakes
-'89 Iroc Z28 Stock 5.7 Edelb. TES headers, Borla Exhaust90K
-'77 Trans Am 468(Stroked) Doug's Headers Flowmaster catback
B & M shift Kit 400 Turbo trans. Edel brock Performer
RPM Intake Sean Murphy built Rochester Carb. Restored
in '08. 3K
#1059528 - 10/21/18 09:46 PM Re: Functional SES after LS swap [Re: jmireles]  
Joined: Apr 2011
Posts: 1,047
Hunter79764 Offline
Member
Hunter79764  Offline
Member

Joined: Apr 2011
Posts: 1,047
Grand Prairie, Tx
Following. I haven't made any changes on mine either, but if you get it all figured out, I might actually get around to wiring mine up too.


Shawn

'85 MC with budget 5.3L swap, TH350 with stock 2.14 rear end
It ain't much off the line, but it's nice on the highway
#1059531 - 10/22/18 03:57 AM Re: Functional SES after LS swap [Re: jmireles]  
Joined: Nov 2008
Posts: 622
jmireles Offline
10+ Year
jmireles  Offline
10+ Year
Member

Joined: Nov 2008
Posts: 622
El Paso, Tx
I found this on YouTube. It hasn't worked for me, so tomorrow I'll call PSI and see what they suggest.

https://www.youtube.com/watch?v=8XrBaMVqGW4&t=2s


-'87 Monte SS LS 2/4L65e Quick Perf. 9" w/disk brakes
-'89 Iroc Z28 Stock 5.7 Edelb. TES headers, Borla Exhaust90K
-'77 Trans Am 468(Stroked) Doug's Headers Flowmaster catback
B & M shift Kit 400 Turbo trans. Edel brock Performer
RPM Intake Sean Murphy built Rochester Carb. Restored
in '08. 3K
#1059532 - 10/22/18 08:27 AM Re: Functional SES after LS swap [Re: jmireles]  
Joined: May 2009
Posts: 2,009
Richie Cat Offline
10+ Year
Richie Cat  Offline
10+ Year
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Joined: May 2009
Posts: 2,009
Lake Ronkonkoma, N.Y.
What pin and plug number did you use for the MIL on you PCM ?

Last edited by Richie Cat; 10/22/18 08:30 AM.

83 SC, 355 w/TPI
#1059534 - 10/22/18 07:25 PM Re: Functional SES after LS swap [Re: jmireles]  
Joined: Mar 2000
Posts: 5,546
upflying Offline
20+ Year
upflying  Offline
20+ Year
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Joined: Mar 2000
Posts: 5,546
Reno, NV
Mine doesn't work either, never thought about needing it. I think my Dakota Digital cluster has a CEL, I'll look the next time I start it.


86 MCSS Notchback coupe, LS3, 4L65E, QP 9", Eaton Truetrac, 4 wheel disc, column shift, Dakota Digital, silver with maroon bench interior

#1059536 - 10/22/18 08:57 PM Re: Functional SES after LS swap [Re: jmireles]  
Joined: Nov 2000
Posts: 2,386
Tunedss86 Offline
15+ Year
Tunedss86  Offline
15+ Year
Member

Joined: Nov 2000
Posts: 2,386
Eastern Virginia
You have to remove the stock lamp driver module. The LS PCM has it built in. I'm looking for instructions that I used.

Last edited by Tunedss86; 10/22/18 08:58 PM.
#1059537 - 10/22/18 08:59 PM Re: Functional SES after LS swap [Re: jmireles]  
Joined: Nov 2000
Posts: 2,386
Tunedss86 Offline
15+ Year
Tunedss86  Offline
15+ Year
Member

Joined: Nov 2000
Posts: 2,386
Eastern Virginia
Here is the instructions I used:

All carbureted computer controlled cars use a Lamp Driver module between the computer and the “service engine soon” or “Check Engine” light. TBI or TPI computer vehicles do not use a lamp driver, instead, are wired directly from computer to SES light. (through the IP harness connector). It will be necessary for you to wire around this lamp driver to make your SES light work correctly with TPI. The Lamp Driver module is taped to the IP harness near the computer harness connector (white plastic 15 pin on my harness) It has four wires going to it. Clip the yellow one, and the white with green stripe wires and join them together. Solder and tape this splice. Now your SES engine light should work correctly with TPI.


Trace one of the two wires you are connecting together back to the stock ecm, & then wire that to the LS PCM wire to drive the CEL.

Last edited by Tunedss86; 10/22/18 09:05 PM.
#1059544 - 10/23/18 05:04 AM Re: Functional SES after LS swap [Re: jmireles]  
Joined: Nov 2008
Posts: 622
jmireles Offline
10+ Year
jmireles  Offline
10+ Year
Member

Joined: Nov 2008
Posts: 622
El Paso, Tx
Success!
I was using the wrong wire. I traced all the wires back to the PCM. PSI said it would be the dark brown wire. Sure enough, I had it labeled. It's been two years since the swap, so I have forgotten details. I cut the tan wire (oil pressure for digital readout) from the yellow wire and connected the dark brown wire to the yellow wire, which was part of the old ALDL port under the dash.
As soon as I turned on the ignition, the SES light came on and back off after a few seconds!
I had mistakenly connected the tan wire.

Last edited by jmireles; 10/23/18 05:06 AM.

-'87 Monte SS LS 2/4L65e Quick Perf. 9" w/disk brakes
-'89 Iroc Z28 Stock 5.7 Edelb. TES headers, Borla Exhaust90K
-'77 Trans Am 468(Stroked) Doug's Headers Flowmaster catback
B & M shift Kit 400 Turbo trans. Edel brock Performer
RPM Intake Sean Murphy built Rochester Carb. Restored
in '08. 3K

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