Maserati Forum banner
1 - 9 of 9 Posts

· Registered
202 Posts
Discussion Starter · #1 · (Edited)
Hello all, I wanted to share my experience with installing an aftermarket radio in my new-to-me 2004 Coupe equipped with the optional auditorium system.

My situation was a bit unique as the previous owner had already removed the NIT and installed a tablet in-lieu of the head unit. Also, he had a line driver installed in between the tablet and the Ask amplifier. I am no audiophile, and the cabin is relatively loud so I was not looking for the best possible sound quality but I wanted to have a better integration and CarPlay capability since I have it in another car and I find it very convenient.

There are several threads on this topic, therefore I won't repeat every single step but I will provide more details on aspects that I did not find fully documented in other threads. My main contributions to the discussion I believe are (1) a more complete integration of the hazard switch and (2) a more detailed explanation on how to route and wire the backup rear camera wiring. Also, because I already had a radio bezel made by the previous owner, I modified that bezel to fit the new head unit instead of using the 3D cad models that others have made. It is not perfect yet, but it will get me going for a while.

Let's start with parts.
Head unit
CarPlay wired USB dongle
ISO harness to power head unit and bring speaker wiring from NIT area to head unit
Antenna adapter
Antenna cable
Buck converter to step down voltage from 12V
Hazard switch
Diodes (I bought them locally, but these should have the same spec)
Connector for hazard switch and center console lighting (you can tap into wires if you like, but it is nice to use a connector)
Pins for the connector (member k1gt2004 advised to buy 173633-1 while digikey suggested to get these one below, I ordered both just in case but I ended up using the ones below, they appear to be identical)
Additional USBs (these are not really necessary, I ended up wiring them because I originally had a different plan in mind)

These are a few threads that I used for guidance. Here I will focus on my "unique" contributions to the topic

First, let me provide an overview of my project:
  • Head unit gets power from ISO connector from NIT
  • Head unit sends RCA output to line driver, then line driver output goes into NIT ISO connector and from there back to the amplifier through the stock wiring (I tried to connect the head unit speaker wires straight into the amplifier, i.e., bypassing the line driver, but it sounded awful, I guess it has to do with levels of the signals).
  • Cigarette lighter illumination wire (white wire) is stepped down to 7V using the buck converter to illuminate the lower center dash buttons
  • Cigarette lighter illumination wire (white wire) is also stepped down to 4V to illuminate the hazard switch when headlights are on (4V is an arbitrary level that I set myself)
  • Hazard switch light is connected to both the headlights signal (see above) and the hazard lights intermittent signal so that I the button illuminates in the dark and it also flahses when the hazards are on. If you prefer the button to be illuminated all the time, wire it to the accessory 12V on the cigarette lighter (red wire)
  • Rear camera is powered by driver side backup light

And this is the finished product.
Car Gear shift Vehicle White Automotive design

Car White Light Automotive design Steering part

Product Vehicle Grey Automotive design Fixture

Quick note on the the hazard switch location.I originally planned to place it at top but there is no room there on the underneath, so I decided to place it at the bottom so that I have room to add other stuff in the future (I don’t have any plans now but who knows).

And now with some details.

Something important that I noticed on my car is that the NIT ISO plug was not "standard". I don't know whether my car was wired differently or what, but the wire next to the ground (on the power side of the connector), was not ACC but constant 12V (i.e., a battery wire). Check yours before wiring. In the picture below I already swapped the wires, but the ISO comes with the red and yellow swapped and all wiring diagrams that I have seen show that them wired that way.
The speaker side appeared to be all standard.
Hand Finger Electrical wiring Cable Thumb

The accessory wire was also connected to the red and white wire that you see below. This is the wire the goes back to the Ask amplifier (behind the battery in the trunk) to turn it on (pin 17 on the harness at the amplifier). This wire was already separated from the harness by the previous owner so I can't provide you with details on how to get to it etc.
However, if you have the auditorium system, you will have to send a signal on pin 17 of the auditorium amp to turn it on.

Sensitive content, not recommended for those under 18
Show Content
Carabiner Finger Rock-climbing equipment Electrical wiring Wrist

The wiring for the hazard switch and the lower dash lighting is as follows. The yellow/black wire needs 7V to illuminate the lower dash. I got this from another thread, I did not investigate further, I tried to apply 7V and it worked, I have no idea how they came to 7V but it appears to work. The buck converter steps down the voltage from the cigarette lighter white cable which turns on when the headlights are on. Wire the buck converter here, and not next to the cigarette lighter because you want the 12V headlights signal available here to get connected to the head unit (which needs it to turn on the backlight on the head unit display at night).

The hazard lights come on when the grey and black wire are connected. I figured out that when this happens, the blue wire sends an intermittent 12V signal that can be used to intermittently turn on the hazard light switch. I think this is a new piece of info for the community.

Joint Human body Finger Thumb Line

Unfortunately, the hazard switch was wired with different colors (compared to the car wiring) so you have to be very careful when you wire it. Below, is how I wired mine, colors mentioned in the photo below are relative to the wires in the photo above (which could be the same for many/all 4200).

I wanted to have the hazard switch to illuminate only when the headlights were ON but to also flash intermittently when hazard lights were ON since I think this is how these buttons usually work in a car.

So the black and gray wire from the head unit area go straight into the blue and green wire of the switch (these are the wires that get connected when you press the switch).
The black wire from the switch goes to ground.
The red wire is fed by two diodes to help prevent back feeding current on the wires. On one diode you can connect the blue wire from the head unit area, this will give you the intermittent flashing when hazard lights are ON. If you also want the switch to illuminate when you have the headlights on (so that you can see it in the dark!) then you can connect the headlights 12V to the other diode. In my case, I wanted it to be dimmed so that when the hazard lights are ON they pop. For that application I used the second buck converter that I had available to lower the voltage to 4V (an arbitrary level that I found empirically). This way when the hazard switch is OFF and the headlights are ON, you get a dimmed light from the switch. If you turn on the hazard lights you get an brighter intermittent flashing. If you happen to turn on the hazard lights when the headlights are off, thanks to the diodes you don't get current flowing on the hazard switch line.

Circuit component Terrestrial plant Electrical wiring Slope Electronic component

As for the backup camera, you need to run an RCA from the head unit to the trunk lid (I considered putting it on the bumper but it looked too low, however it can probably work). Once you have the RCA in the NIT area, you need to remove the rear back seat assembly.

First need to remove the cover behind the rear armrest. Just pull straight back, there is only one clip in the center at the top.
Automotive lighting Hood Automotive design Motor vehicle Vehicle door

Then remove the armrest, there are push pins on either side. The slot in the seat has an opening toward the front to help the pin slide out.

Then you need to undo the 4 15mm bolts. They were super tight on mine, I had to use a breaker bar...

Steering part Automotive design Vehicle door Gadget Vehicle


· Registered
202 Posts
Discussion Starter · #2 · (Edited)
Now that you have the seat back out, you need to lift the seat bottom. There are two clips that hold it in place. You only need to undo the one on the driver side. These are super tight, I had a good fight with it! I am showing a closeup of the clip to help you visualize it.

With the seat bottom up, now you can loosen up the carpet and snake the RCA. Try to route it on the side of the tunnel (as opposed to the top) to avoid putting stress on it. Similarly, route it in front of the rear seat, not directly under the seat bottom. Once you get to the side of the seat bottom you will see other wires there and you can run it next to them.

Electrical wiring Bumper Automotive exterior Cable Audio equipment

Run the wire along the side and then move the insulation to reveal the grommets that will take you to the trunk area. I used the outmost grommet, just push gently the wire that is there to open up the grommet and snake your RCA through.

Automotive tire Audio equipment Electrical wiring Gadget Cable

You are almost there but first you need to remove the boot lining (there is one clip at the bottom of the side lining and I seem to remember one at the top, look carefully before start pulling stuff apart)

Automotive tire Hood Grey Trunk Asphalt

With the lining removed you will finally see your RCA.

Motor vehicle Hood Automotive tire Automotive lighting Automotive design

It is time now to wire the reverse signal wiring to the camera. You need a 12V that comes on when you put the car in reverse. The 12V will go to the camera and back to the head unit to let it know to switch on the rear camera view. The RCA comes wired with a red wire that you will have to connect this 12V source. For this 12V source I used the driver side backup light.

Check carefully your wiring as colors could be different. In my car, the backup light was hooked to a pink wire (it started pale yellow at the bulb and then hooked into a pink wire).

Motor vehicle Auto part Gas Technology Bag

So I tapped into the pink wire and a black ground and ran it forward toward the RCA that I had snaked through the cabin.

Automotive tire Motor vehicle Hood Automotive design Vehicle

You can bundle together your RCA and power wires and run them through an opening that will take you to the top of the trunk opening.

Hood Automotive design Motor vehicle Automotive tire Automotive exterior

I did not want to run the wires outside of the rubber housing as I feared I would get water into the trunk. So I removed the RCA plug (it is too large to go through the rubber hosing) and I snaked the three wires through the rubber housing. This is why you can't see them in the picture (I marked them up just to show the concept). Make sure that you properly reseal the rubber housing endings against the body when you put them back.
Vehicle Motor vehicle Automotive lighting Hood Automotive tire

I forgot to mention that before doing this you need to remove the lining on the trunk lid. It is held in place by a bzillion clips. These are somewhat tight but you just need to work all of them out.
Now you can snake the wiring in the trunk lid and hook it up to the camera.

I decided that I did not have the guts to drill through the trim and since the license plate light housing was already cracked, I simply routed the camera wire through there (there is a thick rubber seal that helps). I secured the camera with a small square of 3M double sided tape. I think it will stay there because there is also the wire holding it in place.

Frankly it does not look super from outside but this is the camera that came with the head unit and the picture quality is quite good. Perhaps I will replace it at some point with a camera that can sit flush with the trunk handle lip. If you are willing to drill, this can be a good option.

Motor vehicle Bumper Automotive exterior Gas Electronic instrument

Now you can hook up the camera to the RCA and 12V switched wire that you just ran through the trunk lid. Check everything before putting panels back together.

· Registered
202 Posts
Discussion Starter · #3 · (Edited)
I know I skimped over the head unit installation but I think that has been fully covered by other posts and general head unit installation instructions. Plus I was lucky to have a bezel already cut out, and that is a project in its own.

Anyway, I had to cut the supporting brackets that came with the head unit in order to attach it to the opening using the screws that hold the AC control panel/shifter in place. Then I simply press fit the bezel that the previous owner had made (I had to open it up at the bottom, this is why it does not look smooth at the bottom).

Rectangle Wood Gas Watch Gadget

This head unit is nice because it is very shallow.

Ruler Office ruler Photographic film Circuit component Tape measure

The USB, GPS antenna, and MIC wire go from the head unit to the glove box (take your time, you will snake them through). The MIC then continues to the right, and you can tuck it into trim gaps to go all the way up the A pillar, roof header, and then clip it to the rearview mirror.
I left the GPS antenna in the glovebox as I am not planning to use it, but I can still pull it up on occurrence.
Finally, the head unit has two USB input. I connected the CarlinKit dongle to the 6 pin USB (powered USB) and from there I ran a USB all the way back to the NIT area (see next pic). I have a USB flash drive with music on the other USB input. I could have tuck the CarlinKit away under some trim but I rather have the flexibility to unplug it, connect straight to it etc. without having to remove trim panels.
Hood Motor vehicle Vehicle Trunk Steering part

The CarlinKit USB cable (i.e., the CarPlay) then comes into the armrest so that I can connect it to my phone and leave it in there or place my phone in the cupholder while still connected. As I mentioned I also wired a 2 outlet USB power supply and these are the two USB that you see in the pic below. I would say that these are really not necessary as you can get a flush mount cigarette lighter USB charger and it will look great in there.

Motor vehicle Automotive design Car seat cover Grey Vehicle door

· Registered
202 Posts
Discussion Starter · #5 · (Edited)
Awesome! Very clean setup, thank you for documenting and sharing your process!
sure, I learned a lot from this forum and I wanted to share.

by the way if anybody sees any problem with my wiring let me know! In particular the diodes stuff (I could have done it with a relay I guess) and the backup light tapping (I know some cars don’t like that).

also, for the CarPlay dongle, it required some fine tuning before it started to work properly but now it appears to be quite solid (that is, CarPlay pops up as soon as the phone is connected and I can keep listening to the radio/music while I am using navigation on CarPlay). I will take some screen grabs of the settings that I used.

· Registered
202 Posts
Discussion Starter · #8 ·

Shortly after completing this installation I put the car in storage and did not get to use the radio much if at all. Upon getting the car back out on the road this spring I noticed a few glitches.

In particular, I discovered that the blue hazard light signal wire provides an alternating 12v signal also when the right turn signal is engaged (in addition to when hazards are engaged). Therefore, my hazard lights switch was flashing when the right indicator was engaged. I got a solution for this and I will post it here after I get the chance to test it a bit more.

· Registered
202 Posts
Discussion Starter · #9 · (Edited)
Let me close the loop on this.

I have put some miles on the car and everything is working as expected so I have confidence in my solution. I can't guarantee that this will work with all cars, so if you decide to follow this approach, do it at your own risk.

As I mentioned previously, the blue wire provides 12V when hazard lights are flashing but also when right turn signal is engaged. Therefore, if you wire the blue wire straight into the hazard switch light, it will flash also when you turn on the right signal.

Finger Thumb Font Line Electrical wiring

Also, please note that the black wire is a true ground. When it gets connected with the gray wires it completes that circuit and turns on the flashers. Therefore what I did was to wire a relay to the gray wire, so that the relay had an open ground until the black and gray were connected to turn on the hazard lights. This way, the relay is not energized when the hazard lights are off and if you turn on the right turn indicator the relay won't pass the 12V to the hazard switch light. I added a diode on the wire from the relay to the gray wire to avoid any back current from the relay.

Below is the diagram of the circuit. The black, blue and gray wire in the "from car" section match the wires in the photograph above.

Font Technology Rectangle Pattern Parallel

Also, in my car the illumination signal was not always 0V when headlights were OFF, and although the voltage was not full 12V it was enough to randomly turn on the head unit back light. Therefore, I added a relay also to the illumination wire so that only when full 12V are provided on the the illumination wire a signal is passed to the head unit (I energized the relay with the illumination wire itself. The low voltage that is present on the illumination wire is not enough to open the relay so the relay passes the voltage only when the full 12V are present).

Finally, I moved the radio a bit further out (it was too recessed) and refinished the bezel as I originally made a rough cut to fit the head unit.
I used Testors spray enamel 1253 graphite gray. I tried different Testors gray colors and this was the closest. Below you can see two photos (with and without flash) to get an idea of the difference in color. In real life it looks better but the match is obviously not perfect and the photos below are intentionally highlighting the differences.

Car Vehicle Automotive design Steering part Personal luxury car

Car Vehicle Automotive design Steering part Mode of transport

Hand Automotive tire Beer Tire Finger

Ah, two semi-related things that can be helpful.
1. My ASK amplifier randomly failed. I opened it but I could not really see anything wrong. Perhaps something simple to fix but for what I use the sound system it was not worth for me to investigate further. So I simply bypassed the amplifier and hooked up the head unit directly to the speakers. I used this excellent guide to bypass the ASK amplifier. It is very simple as the ASK is an added component that can be easily taken out from the system.

2. For anybody evaluating different aftermarket head units. The available depth is approximately 70-75 mm (assuming you make a bezel like mine). Reading below is in millimeters.
Motor vehicle Automotive mirror Automotive design Steering part Steering wheel
1 - 9 of 9 Posts
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.