Hey guys so I am in the process of cleaning up my engine bay wiring to install my freshly built L98, having issues with wiring harness colors not matching the schematics, I bought this car with engine already removed and the wiring harnesses have been butchered quite a bit, figuring most of it out however there are no connectors for knock sensor and fan switch on the passenger side, however the only 2 wires I suspect that would be for them are a white wire and a black wire which in schematics for 88 and later TPI engines could be for the knock and fan, having a hard time with why my car would have harness colors different than the books and manuals are saying it does not appear that it has been changed however I guess I could be wrong? Iv been doing ac delete and removing any wiring and connectors that wont be used like cold start and egr etc. Thanks cheers

 

What was your car originally built as?
...a 1987 IROC-Z with the the TPI-350 Engine (8th digit of VIN= 8) and (RPOs: L98/ B2L)?

Confirm that the 8th digit of your VIN is the NUMBER 8 please.

Is it possible that the Engine-Harness from the passenger-side Fender opening and/ or the C100 Bulk-Head Electrical Connector have been replaced?

The Knock-Sensor Circuit is a very small Circuit.
It is a single 18AWG Dark-Blue Wire that goes from the ESC-Module (Electronic Spark Control) to the Knock-Sensor.

The Knock-Sensor is installed/ threaded into the Cylinder-Block above the Starter-Motor (Passenger-Side of Engine).
The ESC-Module is on the Fire-Wall on the Driver-Side.





If your L98 1987 IROC-Z ONLY uses one Electric Cooling-Fan; the following applies:

-The Fan is activated by the ECM, which monitors the ECT-Sensor (Engine Coolant Temperature).
-NO Thermostatic-Switch is used for this Fan.
-The ECT-Sensor uses a two Wire Circuit; an 18AWG Yellow Wire, and 18AWG Black Wire that connect to the ECM.
-The ECT-Sensor location varies; but should be located in the Intake-Manifold on the Passenger-Side of the Engine.
-The Fan has its own dedicated Relay, that is triggered by the ECM directly; using a 18AWG Dark-Green with White Tracer Wire.

If your L98 1987 IROC-Z uses Dual Electric Cooling-Fans (Heavy-Duty Cooling-Fans); the following applies:

-The primary Fan is essentially the same as what is described in the "Single Fan" information above.
-The Secondary Fan is activated by a Thermostatic-Switch.
-The Thermostatic-Switch should be located on the Passenger-Side of the Engine (most likely in the Cylinder-Head).
-The Seondary Fan has its own dedicated Relay, that is triggered by the Thermostatic-Switch...
An 18AWG Dark-Green with White Tracer Wire, is used from the Relay to the C101 Electrical Connector
(Both are located in the Passenger-Side Radiator-Support area). An 18AWG Dark-Green Wire goes from C101 to the Thermostatic-Switch
(NO White Tracer on the Wire).

 

Hey wow thanks for the extra info and detailed wiring diagrams, yes this is a true 1987 iroc z l98 car vin 8 engine b2l rpo code with dual cooling fans, I just looked at the esc connector and it is a white wire, here is a photo, I have no idea on the history of this car besides the engine was in the back seat when I got it, someone has had the engine out of it before by the looks of things/markings on the block during the rebuild, all the wiring has yellow loom on it I have been in the process of cleaning up the wiring and relooming and cleaning up the engine bay before engine install, I will have a look at the fan relays and see if I can find an appropriate wire for the fan switch however there is a black wire coming out of the harness right next to the said white wire and so far these seem to be the only mystery wires and I have yet to locate the fan and knock sensor wires leading me to believe they are the wires, here is a photo of the harness before I started digging into it.

 

It is obvious that the wiring has been repaired/ cut/ spliced...

So at this point, the Original Wire-Colors could have been changed to any other color.
However, you can back-trace the Wiring:
-The White-Wire coming out of the the ESC Connector at Terminal "E" does go to the Knock-Sensor.
(follow this Wire as far as it goes, and add a new Knock-Sensor Connector if it is missing).

As far as the Electric-Fans go... Tell me which Connectors and Components that you can or can't find.
Are you looking for the Temperature Sensor Connector for the Primary Fan?
Or are you looking for the Thermostatic-Switch Connector for the Secondary Fan?
We can sort through the Wiring that you have.

 

Alright so I have figured it all out the white wire is indeed for the knock sensor and goes directly to the esc plug I used a multimeter for verification, and the black wire is indeed for the coolant fan switch that goes to the back of the passenger side head as I back probed the connector coming from the fan relays that pins from a black wire into a green/white wire to the black wire coming out of the harness, however someone has modified the cooling fan circuit with some ******* wiring aswell which will be easy to reverse I will just have to confirm the fan relays are in working order, here is a photo of the cuts and splices they made looks like they just ran +12v to the blk/red wires and had the coolant fan switch activate both fans, is this a common modification? Thanks again, engine bay is getting close to being ready for the engine will post some photos when I finished the rerouting of all the harnesses and with engine installed.

 

Wow, I am sorry to say it...
But that is bad!

I don't want to be the guy, who tells you that you need to replace the Wiring-Harnesses...
But today I am that guy.

I do not want to go on and on, but I do need to convey to you that the Wiring is beyond hazardous.
Sorry.

 

For your own safety and the cars reliability...
I would get a good used set of Wiring-Harnesses (Members on the Message-Board sell them)...
or I would have a new set of Wiring-Harnesses made (Members on the Message-Board custom make them).

I was honestly considering donating a new set of Wiring-Harnesses to you.
I went to my Shop to see if I had a new Harness (already made) in stock, that was configured for a 1987 L98 Car.

I am sorry to say that I don't have one already made that would work for your car.
Sorry.
I would build one for you if I did not currently have an overload of Customer's Cars.

 

Hey man I have already repaired the harness and it is back to factory and there is nothing left of concern or safety concerns, just because someone has tampered with it does not mean it needs to be replaced, I have been a mechanic for 15 years and i am fully capable of repairing and modifying wiring to acceptable standards and would not move forward with something that would be unsafe or unreliable especially after spending the last 8 months building an engine! thanks for your help with figuring out this cars wiring systems because my haynes manual obviously sucks but I have it all sorted out now and am happy moving forward.

 

I was not looking to offend you.
I actually said nothing of offense regarding your person.

I can respect that someone has been a "Mechanic" for 15 years. It is a great achievement.
I have been a Master Electronics Engineer for 29 years...
If I signed-off on that Wiring-Harness; I would have been Fired and had my Degrees called into question.

I simply wanted to make you aware that the Wiring in your vehicle has not only been "Tampered with"...
But cut and hacked back together in more places than I care to say.

You were actually going to get a NEW FREE Harness from me...
But I did not currently have one.


So sorry, but you have No right to be angered by anything that I have conveyed to you.
So good luck to you, I TRULY hope that you do not have some horrendous car-fire.

 

Hey man I'm totally not offended or angry sorry if my last post made it seem so, totally grateful for your help and offerings! I have lots of experience in wiring and am fully confident on my repairs have my journeyman certificate as an both automotive and heavy equipement technician so I have seen my fair share of hacked up everything haha! Yes if this was a customer's vehicle I would recommend a new harness, for my build I am satisfied for sure, found another surprise today when I dropped the fuel tank seems someone previous has attempted and failed to cut a trap door in the rear compartment, will be welding that back up for sure, reason I bought this car is the body is quite nice and the engine block and trans were still in the back seat, picked it up for only $800, have about $5000 into the build now should be a decent street car. Thanks again for your assistance

 

I am glad to hear it!
You are most welcome.


Enjoy working on the car!