Aftermarket Headunit , wiring harnesses

double0alero

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I figured there's been a few questions on this, so I'll just post up a little deal on the different type harnesses and so forth that are available for the alero.

Aftermarket Headunits, Wiring Harnesses and Class II

This page focuses primarily upon problems that arise from installing an aftermarket headunit into a vehicle that has GM's Class II databus. As an Alero owner, this is Alero/Grand Am specific. While the basic information and concepts will apply to any car the employs the Class II system, part numbers and such are specific to the n-body platform.

When I was attempting to find information regarding wiring harnesses to use in my 2001 Oldsmobile Alero, I was able to find plenty of information. Too much information, almost. Spread out in many places. Sometimes people saying the same thing, sometimes saying different things. On some forums, people with would say that they just used a simple harness and didn't lose chimes! The only problem with that is that they didn't say they have a '99. The 99's don't have the Class II system...they wouldn't have lost them anyway. So someone might read that and then think that they don't need a relocation harness or a replacement interface when, in fact, they do. This is my attempt to bring as much information as possible into one place, as accurately as I can manage.

This page is divided into six sections:
  • Basic Class II info, RAP and Harness Options will help you determine whether or not your vehicle has a Class II system by determining where the warning chimes come from and whether or not you have the retained accessory power (RAP) feature. Based on those two things, you can then see the pros and cons of "the three R's" when you replace the stock headunit: removal, relocation, or replacement interface.
  • Basic Wiring Harness/Antenna Adapters/Dash Kits gives suggestions (including part numbers and prices) for the harness you'll need if you intend to simply remove your stock headunit, along with the two other necessities, an antenna adapter (the stock antenna plug is much smaller than the aftermarket plugs) and a dash kit in which to mount your aftermarket headunit.
  • Relocation Harnesses provides part numbers and commentary about the two most popular relocation harnesses.
  • Replacement Interfaces provides part numbers and commentary about the five Class II radio replacement interfaces currently on the market.
  • Factory Monsoon Audio Systems addresses a few of the common questions about the Monsoon system, including amp location and the mismatched impedance 6x9 coaxial speakers.
  • Sources provides many links to places that I culled this information from. Car owner forums, manufacturer's sites, retailers, etc.
I am also attempting to compile information from people that have successfully installed aftermarket headunits in their Aleros and Grand Ams, I would appreciate your comments. E-mail me at harness@comcast.net or look for me on the Aleromod.com forums (user name: Purple&Black). If you do e-mail me, please provide the following information (so that we can be as helpful as possible to the next people that are trying to tackle this problem):
  • Type of car (Grand Am, Alero, etc.)
  • Model year
  • Type of sound system (Monsoon, "premium", standard, "Sun & Sound" package, etc.) and whether or not you have (or had) the factory-installed amp in the trunk
  • Do you have the Class II system?...Does your car have retained accessory power (RAP)?
  • Which harness you used (and comments as to how it worked)
  • Features that you may have lost (chimes, RAP)
Basic Class II Info, RAP and Harness Options

Class II or not?
GM's Class II data bus connects several electronic components throughout the car. The radio is one of these devices. The Class II system routes the warning chimes (headlights on, low fuel, etc.) through the radio. The radio receives a signal and then sounds the chime through the left front speaker. To check to see if you have a Class II system, listen for your chimes. If they come from the left front speaker, you've got it. If they come from the middle of the dash or somewhere other than the left front speaker, then you do NOT have the Class II system.

What is Retained Accessory Power (RAP)?
Retained accessory power is a feature on most (if not all) recent GM vehicles. While I'm not sure when RAP was included in specific vehicles, it was not introduced on all models simultaneously. RAP provides power to accessories in the car (most notably the radio) after the ignition is turned off. It will stay on for about 10 minutes or until the driver's side door is opened. You probably already know if your car has RAP. If you don't, the next time you get out of the car, turn the car off . If the radio stays on until you open the door, you've got it. To the best of my knowledge, RAP is controlled (at least partially) by the stock headunit. In my own testing, I determined that none of the wires going to or from the headunit carry any voltage to indicate whether or not RAP is active. The radio receives a signal from the body control module telling when to turn on and off. This explanation would also account for the CD player powering up when you open a door or use the key fob (allowing you to remove a CD without turning the car on...and also allowing the radio to send voltage down the remote turn-on wire for the factory amp). It may be that if the stock headunit is removed from the databus that RAP doesn't work correctly because the databus has been interrupted. This may be an incorrect assumption, but I am unaware of a GM car the has RAP that does NOT have the Class II radio. So if you have RAP, check that left front speaker to confirm where the chimes are coming from.

Now that you know whether or not you have a Class II system, you can decide what to do.

If you do NOT have a Class II system, I consider you lucky. Go buy a cheap wire harness and treat the install like any other car you may have owned in the past.

If you do have the Class II system and you intend to replace it with an aftermarket headunit, there are three basic approaches:
  • Remove the stock headunit. Buy an inexpensive wire harness to match up to the factory harness and then connect your aftermarket harness. You WILL lose all chimes...this may not be a bad thing to some people. You will also lose RAP. Since there is no switched accessory lead in the factory harness, your aftermarket headunit will still need a one. Most people will tap a fuse in the driver's side fuse block (often the windshield wiper fuse) and run that wire through the dash and connect it to the red wire on the aftermarket harness. Now your radio will be on if the ignition is at "ACC" or "ON" but will go off immediately when you switch to "OFF". No retained accessory power.
    Pros: Least expensive, easy, no chimes (depending on your point of view...)
    Cons: No chimes, no RAP, must tap fuse and run wire through dash
  • Relocate the stock headunit. Get a relocation harness and move the stock headunit to the trunk (some people have also put it under a seat). The relocation harness will plug into the factory harness in the dash and provide wires for the harness from your aftermarket radio to connect to. Long wires will also lead from the factory harness...long enough to reach the trunk, where you can put the stock headunit. Most kits will include a separate speaker. Connect the proper wires from the relocation harness to that speaker and then mount the speaker somewhere behind the center console. Since the radio is still on the databus, it will pick up the signal to sound the chimes when appropriate and route the signal through the small separate speaker. The aftermarket headunit still needs an accessory switched lead as described above, therefore no retained accessory power.
    Pros: Keep chimes
    Cons: More expensive, no RAP, must tap fuse and run wire through dash
  • Replace the stock headunit with a Class II module. Until recently, this option was not available. The Class II module plugs into the factory harness and provides wires to connect to the aftermarket harness. The module listens to the databus for the chime signals. When it finds them, it either plays the chimes on an internal speaker or it sends a signal to a small separate speaker that you mount behind the center console. The main difference is that the module also listens for the signal to tell the radio to turn on and off with RAP. It then provides a 12 volt lead to connect to the accessory switched lead on the aftermarket harness.
    Pros: Keep chimes, keep RAP, no relocating the stock radio
    Cons: Most expensive
Now that you've seen your options, it's time to choose what you're going to use to accomplish your goal.


http://peripheralelectronics.com/2002/home.asp
 

double0alero

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Basic Wiring Harnesses/Antenna Adapters/Dash Kits



Metra 70-2001 (estimated price: $11)



This is the basic wiring harness to use if you don't have a Class II radio. I'm not sure if this is the harness you'd want if you intend to just pull the stock headunit and lose the chimes and RAP. I'd guess that it is, but I'm not going to look into it since the people that would do that probably aren't looking here...



70-2001 links:

Metra home page
Metra's installer forums
The 70-2001 at Metra's site
Buy the 70-2001 at Crutchfield ($32)
Buy the 70-2001 at PartsExpress.com ($10.50)
Metra 40GM21 antenna adapter (estimated price: $5)



This is the antenna adapter I have. It fits fine. The 40GM21 says it's for "barbless" plugs. There is also the 40GM10 which says it's for "barbed" or "barbless". I've seen different places say different things for the same year. You're probably fine with either one. I won't list places to get this because you can get this anywhere.





American International GMK420 dash kit (estimated price: $15)



I have this dash kit. Fits very nicely in the 2001 Alero. Depending on what year car you've got will dictate what dash kit you need. The GMK420 fits a double-din dash opening. The Metra 99-2001 is also listed for all years of the Alero. These are also easy to find at lots of different places.



Relocation Harnesses



Metra 70-2003T (estimated price: $35)



I believe this to be the most popularly used relocation harness among the people on Aleromod.com and GrandAmGT.com.



70-2003t links:

Metra home page
Metra's installer forums
The 70-2003T at Metra's site
Buy the 70-2003T at PartsExpress.com ($32)
Scosche GM06 (estimated price: $40)



A warning about the GM06: According to Best Buy's installation guide, the proper harness for my car (2001 Alero) is the GM06. When I asked the installer about RAP, he insisted that the GM06 would keep the RAP feature. He told me that this is what they use on the Impala and Monte Carlo, which also have the Class II radio. I was looking at the harness and looking to see where the wires go. I asked him where the red wire was (to provide power to the aftermarket deck). He showed me. I asked him how that wire could possibly be RAP controlled, since there is no wire leaving the stock headunit that carries voltage when RAP is active. He basically just repeated himself that this is what they use in the Impala and Monte Carlo, never mentioning the Grand Am or the Alero. I went home and e-mailed Scosche. A technician replied (very quickly, I might add) with the following:



"The GM06 does not retain the RAP feature. If you want to retain the RAP feature you will need to use the GM09. The GM09 is not a relocation harness, it has a module that replaces the door chime and gives you the RAP feature. It also sends a healthy signal to the BCM [Body Control Module] so there are no service issues."



The picture shown here doesn't include an external speaker, although the GM06 they had at Best Buy did have one in the package. So you may or may not get an external speaker.



GM06 links:

Scosche home page (rather hard to navigate)
The GM06 at Scosche's site
Buy the GM06 at SoundDomain.com ($40)
Replacement Modules



Metra/Ventura Technologies GMRC-01 (estimated price: $60)



This is the harness that seems to be the most popular and most reliable radio replacement interface. As far as I can tell, more people are using this interface than either the Scosche GM09 or the PAC C2R-GM24.



GMRC-01 links:

Metra home page
Metra's installer forums
Buy the GMRC-01 from Circuit City ($60)
Buy the GMRC-01 from Crutchfield ($80)
Scosche GM09 (estimated price: $100)



There was a reference on SoundDomain.com to the GM09 not being compatible with factory keyless entry systems. I e-mailed again about the GM09 and keyless entry, and the same tech as before replied...



"At this time I am unaware of any other issues you may have with the keyless by replacing the factory unit."



I never obtained a GM09, so I never tested it. Hopefully in the future I will have info verifying whether or not it is compatible.



GM09 links:

Scosche home page (no mention of the GM09)
Scosche's "Auto Encyclopedia" (allows you to enter your car and see what dash kit, wiring harness, antenna adapter, etc. you would need...makes no mention of the GM09, however)
Buy the GM09 from SoundDomain.com ($100)
PAC Audio C2R-GM24 (estimated price: $70)



I had access to one of these, so I tried it. It actually didn't work. At all. Well, when I plugged the harness into the factory harness in the dash the module chimed three times. I ended up calling the company and talking to a tech. At this time I pointed out that their application guide said that the 2002 n-bodies were covered and 2001 and before were not. The tech (who did seem very knowledgeable) said that it only meant that they were not able to confirm that it did work with the 2001. It was unclear whether or not they tested a 2001 or not. As far as I had known, there wasn't anything that changed from 2001 to 2002, but I guess there is.



C2R-GM24 links:

PAC Audio home page
The page from PAC Audio's website (C2R-GM24 is the third item on the page)
PAC application guide (.pdf)
Buy the C2R-GM24 from AudioOutfitter ($68)
Buy C2R-GM24 from The Twister Group ($67)
Peripheral GMCO (estimated price: $100)



Peripheral's news release about the GMCO is as such:



"Peripheral Electronics has released a chime module for late model GM vehicles with Class-2 radios (i.e. Cavalier, Impala, Malibu, etc.) This stand-alone unit is for installation of an aftermarket radio into GM vehicles. The GMCO de-codes the chime signal command on the Class 2 data bus and supplies the appropriate warning tone from its’ built in speaker. This Class-2 solution from Peripheral also generates a 12-volt accessory output to power up the aftermarket radio. This eliminates the process of searching for a 12-volt accessory elsewhere in the vehicle. Additionally, the GMCO uses a genuine Delphi chip that enables it to provide a “Healthy Status” report to the Class-2 system. This speeds up the install by eliminating the necessity of retaining the factory radio in the install. The GMCO is the perfect answer for any GM vehicle without OnStar that utilizes Class-2 commands to produce seatbelt, key in ignition or headlight warning chimes."



Note: Please note that it does not say that it keeps retained accessory power. It very well might. It could, since there is a module. But since it doesn't say that it does...it's possible that it doesn't. Something to keep in mind. I'd suggest that you verify that with Peripheral before you buy.



GMCO links:

Peripheral website
Buy the GMCO from AutoSoundGear ($100)
Soundgate GMChime (estimated price: $85)



Soundgate's website states the following:



"...Not stopping there, however, GMCHIME also provides a digitally activated ignition lead. Radios, factory or aftermarket, use an 'ignition' lead that serves to shut the radio off when the vehicle's key is turned to the 'off' position. Some of General Motors' newer hi-tech vehicles utilize a type of digital ignition lead - thus leaving the aftermarket without one to use. Once again, GMCHIME comes to the rescue by providing this very important feature."



Again, it is not clear whether it simply provides an 12 volt accessory lead or whether not it keep retained accessory power. It does say a "digitally activated ignition lead". That should be RAP-controlled.



GMChime links:

Soundgate web site
The GMChime at Soundgate.com
Buy the GM Chime from Logjam Electronics ($90)
Buy the GMChime from TMS Electronics ($80)
Factory Monsoon Audio Systems



Q: How do I know if I have a Monsoon system?



A: There does seem to be some debate about this. Some n-body cars have a "premium" sound system. Then there is the Monsoon system. These may be totally different, but there is lots of debate about it (the kind of debate that doesn't really get settled). Someone who works for GM said that if it doesn't say "Monsoon" on your stock radio, then you don't have the Monsoon system. If you have a factory-installed amp in your trunk (left side, pull away the carpet) that could be a clue. My stock radio does not say "Monsoon" but I have an amp in the trunk that says "Monsoon" on the side. Whether or not I have a Monsoon system I don't know. But this I do know...any questions or answers (remote turn-on, mismatched impedances in the speakers, etc.) that pertain to the Monsoon amp apply to me and apply to you as well, provided that that amp is sitting in your trunk.



--------------------------------------------------------------------------------



Q: Can I just swap out the rear 6x9 speakers with new ones?



A: No. Those are 2-way coaxial speakers with one set of leads for each component. The crossovers for these leads are built into the amp. The tweeter leads are on a 4-ohm channel from the amp and only carry high frequencies. The woofers are on a 2-ohm channel and only carry low frequencies. If you connect standard 4-ohm coaxial speakers to the 2-ohm leads, they won't work at all. If you connect them to the 4-ohm leads, you'll only get high-frequencies, if anything.. Generally, the solution is to replace the headunit and run you aftermarket speakers off the headunit. You could also buy an aftermarket amp to drive your new speakers. Get a subwoofer while you're at it...



You won't be able to find replacement coaxials with mismatched impedances like that except from the dealer, and they're $75 apiece. You may be able to find them used either on eBay or on one of the n-body forums.
 

double0alero

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Q: What's the pinout on the Monsoon amp?



A: Pin Wire Color Function:



E1 LT GRN Right Front Speaker Output (+)

E2 TAN Left Front Speaker Output (+)

E3 GRY Left Front Speaker Output (-)

E4 LT BLU Right Rear Speaker Output (-)

E5 DK BLU Right Rear Speaker Output (+)

E6 BRN Left Rear Speaker Output (+)

E7 YEL Left Rear Speaker Output (-)

E8 BLK Ground

E9 BLK Ground

E10 DK GRN Antenna Relay Coil Supply Voltage

E11 ORN Battery Positive Voltage

E11 ORN Battery Positive Voltage

E13 BLK Left Front Tweeter Speaker Output (+)

E14 YEL Left Front Tweeter Speaker Output (-)

E15 DK BLU Left Front Midrange Speaker Output (+)

E16 LT BLU Left Front Midrange Speaker Output (-)

F1 DK GRN Right Front Speaker Output (-)

F2 LT GRN Right Front Speaker Tweeter Output (+)

F3 PPL Right Front Speaker Tweeter Output (-)

F4 PPL Left Rear Tweeter Speaker Output (-)

F5 RED Left Rear Tweeter Speaker Output (+)

F6 DK GRN Right Front Midrange Speaker Output (-)

F7 ORN Right Front Midrange Speaker Output (+)

F8 PPL Gain Control Signal

F9 -- Not Used

F10 YEL Right Rear Tweeter Speaker Output (-)

F11 WHT Right Rear Tweeter Speaker Output (+)

F12 -- Not Used

F13 LT BLU/BLK Right Subwoofer Speaker Output (-)

F14 DK GRN Right Subwoofer Speaker Output (+)

F15 DK BLU/WHT Left Subwoofer Speaker Outlet (+)

F16 LT GRN/BLK Left Subwoofer Speaker Outlet (-)



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Q: What wire do I use for the remote turn-on wire?



A: E10. Dark green. Don't get it confused with F1, one of the speaker leads.



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Radio Pinout



Recently I saw someone ask for the pinout for the stock radio. Since I had recently replaced mine, I had done a little testing to find out the purpose of some of the less obvious wires. Speaker leads, illumination, ground, battery were easy, but there are quite a few other ones. I was stumped on a few, but then I e-mailed the part # of my radio to Delphi Electronics and requested a wiring diagram. They sent me one. Unfortunately, some of the descriptions are quite archaic and they lack wire colors on their diagram. I added the wire colors as they pertained to the factory harness in my car (2001 Alero, "premium" sound system, Monsoon amp). Those that have no color next to them are not used in my car but may or may not be used in other cars with other options such as a power antenna or steering wheel controls.



The radio pinout is here.





Sources



Information from lots of different sources went into this. Much of it was found on two of the n-body forums, Aleromod.com and GrandAmGT.com. Other information was culled from manufacturers' web sites, phone calls to the manufacturers, my own trial-and-error and various internet searches. If you're looking for more info, I highly recommend the Aleromod.com and GrandAmGT.com forums. There you'll find people that have already installed aftermarket headunits and amps and all kinds of audio equipment into their Aleros and Grand Ams. They will prove to be your best source of reliable information. Below there are quite a few links. A few of the links below will search the appropriate forum for some of the more helpful keywords. If you don't find what you're looking for, search for something else or join one of the forums and ask. You'd be surprised how much other owners know.



Aleromod.com

A very informative post about harness options (by 2ndAlero) | text mirrored here
GrandAmGT.com

GAGT audio forum
GAGT search for "monsoon chimes"
GAGT search for "harness"
Other forums and sites

n-body (Grand Am, Alero)
n-Body.net
gaownersclub.com
gaupgrade.com
j-body (Cavalier, Sunfire)
j-body.org
w-body (Grand Prix)
w-body.org
Retailer sites

SoundDomain.com
Crutchfield
Best Buy
Circuit City
Manufacturer sites

Metra
Scosche
PAC Audio
Soundgate
Peripheral
 

double0alero

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okay, sorry i had to use 3 posts here cause the max data input is 10000 characters...but you get the point...happy reading!
 

TED691977

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Question On An 05 Chevy Colorado Truck

Thank you for your knowledge on this subject. I would ask given your knowledge....do you know what chimes you loose if you do not go with the aftermarket bus ii connector. is it just doors and lights? or are all of the warning chimes connected with the truck disabled such as engine warnings, breaks, etc. disabled? also does this effect the computer of the vehicle somehow not having the stock head unit installed in the g.m. vehicle. My particular vehicle is the 05 chevy colorado pickup truck without onstar but does have the in door tweeters built in.
 

FishKU7

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Wiring Power Issues

I had a Pioneer Super Tuner in my Alero and I want to switch it with my buddy's old Kenwood Excelon (the Pioneer CD player is shot). I have the Alero wiring harness and cut the connector for the Pioneer off and rewired it for the Kenwood. I made sure all the connections were correct because it is wired for a four-channel amp, but when I wired it up, I got no power to the head unit. I'm not ruling out the fact that the head unit may be defective because it is old. Any thoughts or suggestions?
 

2001alerogx

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I used the metra gm06 kit in my 01 alero and just tapped into my pcm ignition fuse in my driver side fuse panel for my switched power and yes i lost my door chime but it has worked seamlessly for years now
 

tunedin925

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im a bit confused. i just bought a 2000 alero 4 dr, put in a aftermarket pioneer deck, wired everything correct, no sound from the rear speakers at all now. i have some 6x9s to put in and replace the stock ones, what am i doing wrong here or what exactly do i need to do ?? my email is ptune17@gmail.com ....please any help would be appreciated, thank you!
 
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