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Ls4 swap wiring issues by Nreid90
Started on: 06-29-2015 08:20 PM
Replies: 13 (635 views)
Last post by: phonedawgz on 07-03-2015 10:05 PM
Nreid90
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Report this Post06-29-2015 08:20 PM Click Here to See the Profile for Nreid90Click Here to Email Nreid90Send a Private Message to Nreid90Edit/Delete MessageReply w/QuoteDirect Link to This Post
So my build is slightly different. The ls4 is going on a Nissan 240sx but I have run into electrical issues. When I hook the battery up and put the power wire to the fuse box it's starts cranking. I have no fuel running to the engine yet and I am also not getting spark. I have the Tcm and ecm hooked up and I'm not getting power to the dash. It's seems like the fiero guys are experts on the ls4 swap and I was looking for assistance to get my car running. Any info would really help and if you need pics or anything please let me know and I will show you everything I can. Thanks fellas
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phonedawgz
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Report this Post06-29-2015 08:59 PM Click Here to See the Profile for phonedawgzClick Here to visit phonedawgz's HomePageClick Here to Email phonedawgzSend a Private Message to phonedawgzEdit/Delete MessageReply w/QuoteDirect Link to This Post
What did you do for a wiring harness?

What are you doing for VATs?

When you hook up a scanner to the PCM does it connect?

Does the PCM turn on the fuel pump relay or are you just hot wiring it?
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Nreid90
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Report this Post06-29-2015 10:50 PM Click Here to See the Profile for Nreid90Click Here to Email Nreid90Send a Private Message to Nreid90Edit/Delete MessageReply w/QuoteDirect Link to This Post
It's the stock harness from a 2007 Monte Carlo ss donor car.
What exactly is vats? I'm usually he the stock key and immobilizer
I don't have the fuel hooked up I was going to just hot wire it to a switch for safety purposes
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Nreid90
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Report this Post06-29-2015 10:54 PM Click Here to See the Profile for Nreid90Click Here to Email Nreid90Send a Private Message to Nreid90Edit/Delete MessageReply w/QuoteDirect Link to This Post

Nreid90

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Member since Jun 2015
I haven't tried to hook up a scanner yet but I will try tomorrow afternoon and see if it's getting power
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Nreid90
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Report this Post06-30-2015 10:48 AM Click Here to See the Profile for Nreid90Click Here to Email Nreid90Send a Private Message to Nreid90Edit/Delete MessageReply w/QuoteDirect Link to This Post
No power to my dlc right now. I will start at the starter and trace the wires back and see why the fuse box is not sending power to other components
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phonedawgz
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Report this Post06-30-2015 07:05 PM Click Here to See the Profile for phonedawgzClick Here to visit phonedawgz's HomePageClick Here to Email phonedawgzSend a Private Message to phonedawgzEdit/Delete MessageReply w/QuoteDirect Link to This Post
Hot wiring the fuel pump to a switch is unsafe.

I make swap harnesses. Trying to put an engine harness from a different car in is extremely problematic.

[This message has been edited by phonedawgz (edited 06-30-2015).]

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Nreid90
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Report this Post07-01-2015 10:47 PM Click Here to See the Profile for Nreid90Click Here to Email Nreid90Send a Private Message to Nreid90Edit/Delete MessageReply w/QuoteDirect Link to This Post
It's not dangerous if you know what your doing
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olejoedad
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Report this Post07-02-2015 07:01 AM Click Here to See the Profile for olejoedadClick Here to Email olejoedadSend a Private Message to olejoedadEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by Nreid90:

It's not dangerous if you know what your doing


Please elucidate.

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Dennis LaGrua
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Report this Post07-02-2015 08:06 AM Click Here to See the Profile for Dennis LaGruaClick Here to Email Dennis LaGruaSend a Private Message to Dennis LaGruaEdit/Delete MessageReply w/QuoteDirect Link to This Post
The fact of the matter is that you cannot throw a stock LS4 harness on a swap application and expect it to work. Even if you reuse the LS4 power center/fuse box , at the minimum there are 7 or 8 new connections to make. The LS4 PCM in a different application also isn't seeing the inputs of the body control module, antilock brake module, auto transmission and the VAT signal. This is why it is customary to rewire and reprogram the PCM for the new application. I would remove the harness and send it to a professional that can streamline the harness and make it work.

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fieroguru
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Report this Post07-02-2015 08:07 PM Click Here to See the Profile for fieroguruSend a Private Message to fieroguruEdit/Delete MessageReply w/QuoteDirect Link to This Post
Its been 2 years since I did my 07 LS4 swap and my service manuals are buried in storage... so some of these comments won't be a precise as I would like.

Your car is an 07 and the BCM is more highly integrated into the engine controls than the 06 and earlier LS4's. Without it, the ECM will not see the brake switch (brake pedal pressed) to trigger the starter crank function. The brake switch is wired to the BCM and then communicates with the ECM/TCM via the GMLAN wires.

The ECM triggers the starter relay control (C1 Pin 26), but the input from the stock LS4 ignition switch goes to the BCM first and then communicates the start command to the ECM via the GMLAN wires.

Also, the ECM sends the power up signal to the powertrain relay panel (C1 pin 40) that energizes all power feeds to the coils, injectors, etc... However, the signal from the ignition switch still goes through the BCM and GMLAN to get to the ECM.

VATS/PASSKEY resistor values from the key are also sent to the BCM and it sends a pass/fail signal to the ECM. You can turn off this check within the ECM


Most (but not all) of the Fiero LS4 swaps have had the harnesses reworked to eliminate the LS4 fuse panel and BCM. They used the stock Fiero fuse panel for all power feeds to Coils, Injectors, ECM, O2 sensor, etc... They also used the stock Fiero engine harness wiring for the starter function and other basic engine functions. Once this is done, then you just have to keep the ECM happy and turn off the DTCs that will be set.


At least in the 07 Impala SS calibration, removing the BCM did not set a single DTC for me.
As long as there is power to all needed components, the ECM will allow the engine to start without use of the ECM starter relay control (like when using car chassis starter wire), but it will set a DTC that can be turned off.
You will also get DTCs for the fuel tank sensor and brake booster sensor if those are not wired up, but those can be turned off.

You will need to do some reworking to your stock harness to get it to run... its not as simple as just setting it in place and turning the key.

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fieroguru
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Report this Post07-02-2015 08:16 PM Click Here to See the Profile for fieroguruSend a Private Message to fieroguruEdit/Delete MessageReply w/QuoteDirect Link to This Post
You might find these documents handy as it shows the pinouts for the ECM, what they do, and what I did about them. The 203 and 500 connector references are Fiero chassis wiring connections. The other The thing to keep in mind on the section TCM is that my swap was with a Manual transmission, but I kept the TCM and tricked it into being happy.

 
quote
Originally posted by fieroguru:

Speaking of documenting... I am nearly done with all the ECM/203/500 termination documentation (might have a few typo's still) and I hope the E67 LS4 guys will find this helpful.

EDIT: Drawings updated for some revisions on 10/18... If you saved the earlier versions, delete them and save the current ones.









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Neils88
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Report this Post07-02-2015 08:27 PM Click Here to See the Profile for Neils88Click Here to Email Neils88Send a Private Message to Neils88Edit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by Nreid90:

It's not dangerous if you know what your doing


The fact that you have said this makes some people believe that you don't know what you are doing.

For it to be safe, your set up would need to shut down the fuel pump in the event that the engine stops...and it needs to do this without human intervention. Is this how you plan on setting it up, or are you just putting in an on/off switch?
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Nreid90
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Report this Post07-03-2015 07:49 PM Click Here to See the Profile for Nreid90Click Here to Email Nreid90Send a Private Message to Nreid90Edit/Delete MessageReply w/QuoteDirect Link to This Post
neils88- why are you going to post an ignorant statement. I am here looking for information about a swap. You saying to someone they don't know what they are doing is an insult considering the fact people have done it before, just on a different platform. If you can't provide useful knowledge I can use, then why post on my thread.

Fieroguru- thanks for the diagrams. I am using all the stock components from the donar car (pcm, bcm, tcm, ignition, abs module, brake switch, etc.) all the parts were saved. My issue now is the car will not crank with everything hooked up. The ign has power and the dash turns on, my dlc scanner is picking up faults and the car info screen is working. I don't know where to start at this point. The diagrams should help. Thank you again for those and I will continue poking around.
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phonedawgz
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Report this Post07-03-2015 10:05 PM Click Here to See the Profile for phonedawgzClick Here to visit phonedawgz's HomePageClick Here to Email phonedawgzSend a Private Message to phonedawgzEdit/Delete MessageReply w/QuoteDirect Link to This Post
Seriously if you hot wired the fuel pump with a switch and consider it to be safe you don't know what you are doing.

I hope you don't die in a fire that results from a crash. I hope that no one else dies in that fire. If they die but you live you could be imprisoned for negligent homicide.

https://en.wikipedia.org/wiki/Negligent_homicide

[This message has been edited by phonedawgz (edited 07-03-2015).]

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