One of the plugs could be for the power steering rack pressure sensor that the Fiero also does not need.
The easiest way to sort things out is measure with a meter from the connector back to the PCM and find the right pin then check with your wiring diagrams to see what it is for. Dan

Thanks Dan for the info. Might get a bit of time this afternoon to sort some more things out.

Steve

Ok...its been a while but I had to put this on the back burner for a bit but have made alot of needed progress on the engine and transmission. I am about to finish up the harness but still have 3 plugs Im not sure about and when I got the harness, it was cut loose from the plugs and with duplicate color wires, Im not sure which was which.



1. ? no idea but im sure its something stupidly simple.

2. and 3. I believe are for the Auto tranny that I am not using. They both have 2 wires each but some are faded or maybe from another year than Ryans pin-out so the colors dont match up.

4. Maybe the Auto tranny also and with only 2 wires,a green w/black and a (pinkish) one that runs to the O2 sensor in the exhaust manifold.

Now that I think about it, one of these might go to the evap canister on the donor?

EDIT sorry for the blurry pic I forgot to add lol
Thanks for any help...again.

Steve

[This message has been edited by JumpStart (edited 03-12-2009).]

Bump?

if you cant find something to plug those random plugs into, then you dont need them obviously enough....

The purple wire should run to your starter in some fashion. I imagine you should run it to the range selector on the transmission, which is a purple wire that same size on the "big" connector. The starter "command" wire runs from the c500 to the range switch via the yellow wire.

I have yet to remove the harness from the Fiero ( too dang old to be pushing the car around unneccarily )so some of this may be self explainatory after I do, but on Ryans pin-out, some of the wires from the Blue and Clear plugs run to either the C500,C203 or the ICM. Are they "spliced in" (leaving the wires already there) or do they "replace" wires that are removed?

Thanks, Steve

quote Originally posted by JumpStart: I did find the last wire (hopefully) that I am not sure of. The water tempature sending unit under the Thermostat housing has 3 wires. Yellow , Black and dark Green. I see no place to use the Green wire on the pin-outs.

Steve the green wire should run to C500 C2 (Dark Green/White). This is the feed to your temp gauge. (the pcm just fires the temp warning light)

Reference: 3800 obd2 wiring swap questions with lots of pictures - Pennock's Fiero Forum:
https://www.fiero.nl/forum/A...070315-2-074653.html

The 3 wire plug to the thermostat housing should be connected to another 3 wire flat plug that runs to your wiring harness. There will either be a green wire that goes nowhere or be 2 wires instead of three. The 2 wires that should remain regaurdless are yellow and black, both going to your PCM. The green wire is spliced in the C500 for your temperature gauge feed. I forget exactly which wire on the C500 it is but if you have the pinout, you should be able to find it.

Ok...the only dark green wire I can find on the pin-out is #75 Blue which is the "Engine Hot Warning Lamp control" that runs to the D3 pin of the C500.

Does this mean that I need to splice these 3 locations together?

1. Blue connector pin #75 (ECM)
2. Pin D3 of the C500 (Fiero)
3. The green wire from the Coolant Tempature sending unit (3800 under the thermostat housing)

Part of the confusion on this is that the harness was cut up a bit due to removing it from the donor car I believe. Would have been alot easier if it were all in one piece.

Thanks Bubbajuju and Flyboy

Steve

quote Originally posted by JumpStart: Does this mean that I need to splice these 3 locations together?

No.

Blue 75 connects to C500 pin D3. This is the PCM telling the idiot light (temperature) on your dash to come on if your coolant is too hot.

The green wire on your coolant temp sensor (below your thermostat housing) gets wired to C500 pin C2. This is the CTS telling the temp gauge needle on your dash to move hotter or cooler.

[This message has been edited by Bubbajuju (edited 03-22-2009).]

Thanks, I will wire the green up this way but I dont understand why I cant see it on Ryans pin-out?

One other thing...What is "HO2S Sensor 1 heater" on the pin-out? One is a ground and the other goes to pin K of the C203.

Thanks Bubbajuju

Steve

quote Originally posted by JumpStart: Thanks, I will wire the green up this way but I dont understand why I cant see it on Ryans pin-out?

It's not there. I emailed him when I was wiring my temp sensor and he helped me get it right. (I was confused because my harness dead-ended the green wire an inch after the connector, so I had to add wire to run it to C500)

quote Originally posted by JumpStart: One other thing...What is "HO2S Sensor 1 heater" on the pin-out? One is a ground and the other goes to pin K of the C203.

Steve I'm not sure but I think the "H" stands for "Heated" hence Heated Oxygen Sensor 1 (pre-cat)
The 02 Sensor should have four wires: Signal Low, Signal High, Ground and 12volts (which is the wire going to pin K, this allows it to pre-heat)

[This message has been edited by Bubbajuju (edited 03-22-2009).]

Thanks once again and just gave you a Big plus. I now seem to have all the wires from the ECM to the engine wired up,and to the C500 and the C203 sorted out.

I now have a few wires from the ECM (about 9) left. Im thinking that I cant use some of them anyway but best to be sure.

They refer to...
High speed fan control [blue 5]
Intake air temp sensor (in the boot just before the TB?) [blue 17]
Vehicle Speed sensor (transmission?) [blue 64 and 65]
Trans gear selector position switch [blue 68 / clear 18 and 56]
OBD2 datalink conector (no idea unless its the ALDL from the donor which I dont have) [blue 15 and 59]

After this I should be able to wrap up the harness.

Thanks for your patience Bubbajuju

Steve

quote Originally posted by JumpStart: They refer to... High speed fan control [blue 5] Intake air temp sensor (in the boot just before the TB?) [blue 17] Vehicle Speed sensor (transmission?) [blue 64 and 65] Trans gear selector position switch [blue 68 / clear 18 and 56] OBD2 datalink conector (no idea unless its the ALDL from the donor which I dont have) [blue 15 and 59]

High speed fan control just gets deleted.
Intake air temp sensor needs to be connected. Also wire it's ground which goes to PCM Blue 17.
Trans gear selector and all tranny wires (except vehicle speed sensor) get deleted

Then head to the junkyard and grab a OBD2 datalink connector off of any say 1998-2002 GM car. (its the blue computer interface connector usually found under the dash on the drivers side)
Wire the two PCM wires to it and then it needs grounds wired at pin 4 and 5 (of the connector) and constant 12 volts at pin 16 (of the connector) I think I grabbed the power off of my cig lighter. And then I just have my OBD2 connector stored behind the cig lighter plate on the center console.

Now on the Vehicle Speed Sensor I can't help you much. I don't have any experience with a 92 transmission so I don't know how it is wired. Also I don't know the pulse width it is going to put out. All I can tell you is that your PCM needs to be connected to it (high and low signal).
What I did with my wiring was just splice my PCM wires into my Transmission VSS. That way the PCM got it's feed and my speedometer got its feed.

I would email Ryan at Sinister if it were me. www.gmtuners.com

Well this has given me a headstart and 4 more wires to lose. I will check on this Mon afternoon and I am assuming that the OBD2 data link is the same thing as what is in the Fiero console to check for codes? (jumper A and B) ?

Thanks again,

Steve

quote Originally posted by JumpStart: ...I am assuming that the OBD2 data link is the same thing as what is in the Fiero console to check for codes? (jumper A and B) ?

It is. It's just a different connector with a different pinout. You need it to run cool scan gauges and diagnostic software. Also if you have a check engine light you can take it up to autozone (or whatever parts chain is near you) and get it scanned for trouble codes for free.

Ok...I now have the exhaust manifold to replace the cracked one and the rubber tubing with the intake air tempature that fits on the throttle body. Its getting closer.

I remember seeing in a thread that someone had found radiator hoses and had posted the part number that would fit in place with some shortening of one or both of the hoses but I cant find it. Anyone know the make/model or part # of the radiator hoses that would fit?

Thanks, Steve

quote Originally posted by JumpStart: I remember seeing in a thread that someone had found radiator hoses and had posted the part number that would fit in place with some shortening of one or both of the hoses but I cant find it. Anyone know the make/model or part # of the radiator hoses that would fit? Thanks, Steve

I can't find that thread off hand but I went with Autozone L-251 and XL-1023. The passenger side I trimmed an inch off at the motor but shouldn't have. It was better left alone. The driver's side is a little fat so I used multiple clamps to attach it top and bottom. The setup has worked great and the hoses fit like they belong as far as the length and bends.

Thanks once again Bubbajuju.

Steve

Ok...back once again...lol

I have now found that the only wire on the pin-out for the Alternator is 61 clear that goes to B or L of the Alternator. 61 Clear is a red wire and im sure it goes to the red wire on the Alt. but what about the other two wires ( blueish/greenish) comming from the Alt.?
Where do they go?

Also I noticed that my 2 oil sending unit wires (tan/black and black/white) have nowhere to go. Help??? I must be missing something here.
Thanks, Steve

[This message has been edited by JumpStart (edited 04-13-2009).]

oil sending unit only uses 1 wire for the gauge, the rest are unused.

quote Originally posted by JumpStart: Also I noticed that my 2 oil sending unit wires (tan/black and black/white) have nowhere to go. Help??? I must be missing something here. Thanks, Steve

Tan/Blk goes to the fuel pump relay, Blk/Wht is Chassis ground

quote Originally posted by Mike Gonzalez: Tan/Blk goes to the fuel pump relay, Blk/Wht is Chassis ground

Why would you wire the oil sending unit directly to the fuel pump relay? lol


Steve

quote Originally posted by darkhorizon: oil sending unit only uses 1 wire for the gauge, the rest are unused.

Roger that

[This message has been edited by JumpStart (edited 04-14-2009).]

quote Originally posted by JumpStart: Why would you wire the oil sending unit directly to the fuel pump relay? lol Steve

The oil sender work as a backup to your FP relay. If the fuel pump relay goes bad it will still run the fuel pump when there is oil pressure. You dont need to run it, but it is the way the Fiero is originally wired.

quote Originally posted by JumpStart: Ok...back once again...lol I have now found that the only wire on the pin-out for the Alternator is 61 clear that goes to B or L of the Alternator. 61 Clear is a red wire and im sure it goes to the red wire on the Alt. but what about the other two wires ( blueish/greenish) coming from the Alt.? Where do they go? Also I noticed that my 2 oil sending unit wires (tan/black and black/white) have nowhere to go. Help??? I must be missing something here. Thanks, Steve

Steve did you figure it out?
On the alt you only need the large red wire and the small red wire. The other two you can dead end somewhere because you don't need them in this application. Then the PCM lights up the alt light by connecting C203 (B3-should be a brown wire) to PCM Blue 36. The gauge just reads off the 12 volts it gets from anywhere.

As far as the oil pressure... I gutted out my gt gauges (center console) and turned that area into a three gauge system. I made it- oil pressure, boost psi and voltage. (all cheap Sun aftermarket gauges)
Off of my oil pressure nipple on the block I added a tee. I then used the stock 3800 oil pressure sensor to ground an idiot light (which I don't have connected but could use the "shift light" or whatever for this app. Then on the other side of the tee I used a cheap Sun pressure sender that wires to my cheap Sun oil pressure gauge.
It is my understanding that if you use an '88 Fiero oil pressure gauge then it grounds your idiot light and also sends a resistance signal to your gauge. I think the '88 is recommended only because of it's better design. Anyhow if you want to go with the '88 Fiero sending unit to use the stock oil pressure gauge and idiot light then the wiring should be in your service manual.
By now you probably have it figured out, but hey...

(P.S. I only went with the Cheap Sun unit because the sender and gauge was half the price of a replacement Fiero sender and my old Fiero sender and gauge always gave me trouble.)

[This message has been edited by Bubbajuju (edited 04-18-2009).]