PFF - Pennock's Fiero Forum, PDA Edition

3800 swap harnesses (Page 15/20)

can_add

MAR 13, 09:53 AM

ok so I found the performance shift Pin. C2 Pin 21 (for a 98 gtp anyways)

quote

Originally posted by Dennis LaGrua:
The GTP oil pressure sender won't drive the oil pressure gauge as its a switch not a gauge sensor. You'll need to use the 88 Fiero V6 sender. Also be advised that the temperature gauge will reqire that you sue the early GTP ETS 3 pin sensor. The center pins on thse sensors are the gauge connections. As for the sport mode switch, I don't see this on any of the PCM diagrams that I have.

Now I'm a little confused for the ECT I have 3 wires.

1 Green - C500 C2
1 Yellow - C2 Pin 26
1 Black - PCM Ground

is this not correct?

The oil pressure I don't know why this is confussing me so much. So I replace the 3800sc oil pressure sensor with a 88 oil pressure sending unit (would my 85 iron duke one work?) Then wire it up Tan/Black to C2 pin 19, Black/White - chassis ground, and third wire to the gauge. Is this correct? Where do I hook into the gauge from, C203 Pin E?

thanks for all the help guys!

Flyboy81

MAR 20, 12:29 AM

Im just curious here, but I was told that I could wire pin A on the oil pressure sender, the sender wire, to the gauge and it should read. Is this correct? I guess it would be like running a single wire oil sender? Ive got some SS Competition gauges and it has a sender hookup, + and -, and then the gauge light. I assume that it will run a single wire. Anyway just kinda wanted to see if anyone might be able to enlighten me here.

Dennis LaGrua

MAR 20, 07:49 AM

quote

Originally posted by can_add:

ok so I found the performance shift Pin. C2 Pin 21 (for a 98 gtp anyways)
Now I'm a little confused for the ECT I have 3 wires.

1 Green - C500 C2
1 Yellow - C2 Pin 26
1 Black - PCM Ground

is this not correct?

The oil pressure I don't know why this is confussing me so much. So I replace the 3800sc oil pressure sensor with a 88 oil pressure sending unit (would my 85 iron duke one work?) Then wire it up Tan/Black to C2 pin 19, Black/White - chassis ground, and third wire to the gauge. Is this correct? Where do I hook into the gauge from, C203 Pin E?

thanks for all the help guys!

As for the ECT. The center pin #C DK Green Wire is the sensing output to the temp gauge (connect to pin C2 on the C500 connector. If you had a Duke engine this wire should be tan). Pin A Or/Bl wire is the ground (low ref) and B Yellow is the temp sensor signal that goes to the PCM.

As for the oil pressure sensor. My wiring uses the GTP fuze box and fuel pump relay wiring so I only connected pin C ( the center pin) of the oil pressure sender to pin E tan wire on the C203 connector. Again use the 88 oil pressure sender which provides a 90 ohm resistive output at full pressure. There are many aftermarket senders out there that are sold as 88 Fiero oil pressure senders but provide a 120 ohm output that will pin your gauge. Use only the AC Delco senders. I wanted to get finsihed and ran down to Autozone and used an aftermarket sender and had to add a 300 ohm parallel resisitor to prevent the gauge from pegging. They sold me a generic 120 ohm sensor!!! Apparently many GM cars use a sender that looks just like the 88 Fiero unit but put out a different resistance. If you can reuse your old working Fiero sender that will work too but if it is that big can type fittiment issues can result.

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" THE BLACK PARALYZER" -87GT 3800SC Series III engine, 3.4" Pulley, N* TB, LS1 MAF, Flotech Exhaust Autolite 104's Custom CAI 4T65eHD w. custom axles, HP Tuners VCM Suite.
"THE COLUSSUS"
87GT - ALL OUT 3.4L Turbocharged engine, Garrett Hybrid Turbo, MSD ign., modified TH125H
" ON THE LOOSE WITHOUT THE JUICE "

[This message has been edited by Dennis LaGrua (edited 03-20-2009).]

bc12dJohn

MAR 20, 02:19 PM

I just have to jump in to say 'thank you'. As I followed this thread, it FINALLY sunk in that the one tan wire at C203, E drives both the gage and the warning light. I am using an '88 Fiero oil pressure sender with my 3800. I had made an 'oil light relay' (similar to the one used in some late 80s GMs, like the Park Ave with the digital dash). I was going to use the switch to operate a relay (rather than a back-up for the fuel pump) that would open the light circuit when the switch closed at pressure. Thanks on this one, especially to Dennis and Dan. This discussion has been very informative and enlightening! John

Dennis LaGrua

MAR 20, 02:27 PM

quote

Originally posted by bc12dJohn:

I just have to jump in to say 'thank you'. As I followed this thread, it FINALLY sunk in that the one tan wire at C203, E drives both the gage and the warning light. I am using an '88 Fiero oil pressure sender with my 3800. I had made an 'oil light relay' (similar to the one used in some late 80s GMs, like the Park Ave with the digital dash). I was going to use the switch to operate a relay (rather than a back-up for the fuel pump) that would open the light circuit when the switch closed at pressure. Thanks on this one, especially to Dennis and Dan. This discussion has been very informative and enlightening! John

I would not worry too much about the fuel pump (back up) secondary circuit on the oil presure sender. I just carry an extra fuel pump relay in the glove box. In the rare case that the relay goes out, I'll just plug in a new relay and get going again.

------------------
" THE BLACK PARALYZER" -87GT 3800SC Series III engine, 3.4" Pulley, N* TB, LS1 MAF, Flotech Exhaust Autolite 104's Custom CAI 4T65eHD w. custom axles, HP Tuners VCM Suite.
"THE COLUSSUS"
87GT - ALL OUT 3.4L Turbocharged engine, Garrett Hybrid Turbo, MSD ign., modified TH125H
" ON THE LOOSE WITHOUT THE JUICE "

FIERO1985

MAR 27, 12:55 AM

did you ever get my pm dan?

can_add

MAR 27, 09:40 AM

quote

Originally posted by FIEROFLYER:

For the 98 GTP PCm the tan with black wire from the oil pressure sensor goes to PCM C2 (clear) pin 19 and the black with white goes to chassis ground. With a three pin sensor like the 88 Fiero used the third wire is for the gauge. Dan

I'm just wondering about this wire that goes to C2 Pin 19 - In all my pinout diagrams C2 Pin 19 is not used. So what is the point of running this wire?

Emc209i

MAR 27, 10:17 AM

Trick question? There is no point, pull it out of the connector.

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FIEROFLYER

MAR 27, 07:46 PM

The 97/98 GTP used it for oil pressure info and the 99 up GTP stopped using it. The Regal as well as many other GM vehicles that have serial data fed gauges continued to send oil pressure info to the PCM but only for feeding the oil pressure gauge.
So the oil pressure info is not needed on the GTP PCM's. Dan

Dennis LaGrua

MAR 27, 09:58 PM

quote

ok so I found the performance shift Pin. C2 Pin 21 (for a 98 gtp anyways)

Just for everyones reference; On the 2003 GTP PCM C2 connector, pins 19-21 are not used. Apparently this "performance shift" mode was only used on the earlier 4T65eHD's transmissons. I summize that it was eliminated on the 2003-up trans.