05’ 300C RS issue

Printed From: the12volt.com
Forum Name: Car Security and Convenience
Forum Discription: Car Alarms, Keyless Entries, Remote Starters, Immobilizer Bypasses, Sensors, Door Locks, Window Modules, Heated Mirrors, Heated Seats, etc.
URL: https://www.the12volt.com/installbay/forum_posts.asp?tid=52979
Printed Date: May 08, 2025 at 12:56 PM

Topic: 05’ 300C RS issue

Posted By: JoshV
Subject: 05’ 300C RS issue
Date Posted: April 01, 2005 at 1:41 AM

Ok so heres my issue. Some how upon RS it triggered a check engine code and now the light is on. I was going to just disconnect the +battery terminal and ground it to re-set the ecu but I dont know if that is such a good idea on this car. I dont know if anything after doing this would have to be re-set.

I tried talking to the dealership but of course they were of NO assistance. The interesting part about the wiring was the "MUX" wire in the ignition harness. The bypass I used was a 555U and I took the circuit board out of one of his keys.

Overall I really like the car. The prewire for the RS/Alarm kinda sucked but everything is else is pretty easy. I also did a AVIC N2 and I had to bypass the factory Boston amp. I used the rear outputs to drive the woofers in the doors.(gotta love pioneer for have a low pass output to drive a sub from the headunit) Then the dash and rear speakers are 2 ohms so I had to run those in series on the front 2 channels from the headunit. It actually sounds pretty nice minus not having actual front to back fade.

If anyone has any ideas as to how to re-set the ecu that would be great. Or if anyone else has had this problem, what caused it? I have been installing for quite a few years now and I totally felt comfortable working on the car and to the best of my knowledge its wired correctly. The only thing that I can even think that might be wrong is the "MUX" wire in the ign harness.

Thanks in advance

Replies:

Posted By: NowYaKnow
Date Posted: April 01, 2005 at 6:07 AM

I would disconnect both battery terminals for about 10 - 15 minutes.. (short them together briefly if you feel comfortable)

Did you cut the PURPLE / brown wire to isolate it? What value resistors did you use for the 2nd starter and the accessory? How did you wire them? Also I've only used NKR (no key required) bypasses on this car, but I don't see why a key in the box wouldn't work.

Mike

Posted By: prdjr165
Date Posted: April 01, 2005 at 6:30 AM

I am doing one of these cars on saturday,keep us posted on what you find!

Posted By: dare_ds69
Date Posted: April 01, 2005 at 6:00 PM

i did one and the second staret is confuse the color so the check engine come on, i disconect the battery for 5 minutes and i swith the wires and it work fine

-------------
how own your mind, control your life.
MECP certified. always use a DMM

Posted By: JoshV
Date Posted: April 03, 2005 at 6:53 PM

ok figured it out. The wiring diagram for the " MUX" that I got was waaayyy of base(thanks wire magic) The DEI wire info is right on as usual. Note* The battery is in the trunk, and if it is disconnected it will re-set.

Posted By: prdjr165
Date Posted: April 03, 2005 at 9:20 PM

What is the DEI info?I used the crimestopper info and my gauges are out.

Posted By: prdjr165
Date Posted: April 03, 2005 at 9:20 PM

I have the ignition hooked up like this,
86.- from r/s
85.to pink/white ignition wire
30.to violet/tan body side
87.to violet/orange (mux ground)w/500ohm resistor
87a.toviolet/tan key side

violet/tan acts as a second ignition & 2nd start wire.is it possible that the problem is here at the relay?