DIY: Hardwire a Hella TC-400 TPMS Into Your E46

[G. P. Burdell]

Added 10/29/07:
Please be sure to read the entire thread and the Bimmerfest thread linked in post #13. Hella is apparently working on an issue with the receiver.

Added 11/21/07:
The Tire Rack has put the kit back on their Web site, but the product listing now recommends against installing this kit in cars with aftermarket window tinting.

Added 8/22/09:
I relocated the receiver to the center console several months ago and am happy to report that I haven't had a single loss-of-signal issue in warm weather since.

This weekend, I installed the Hella TC-400 tire pressure monitoring system (TPMS) in my E46 330i. Saturday, BimmerDawg and his staff at Butler Tire installed the pressure transmitters along with a new set of tires, and on Sunday, I hardwired the receiver and display into the car's interior.

For details of TPMSs in general, I will refer you to my previous thread on the SmarTire Gen II TPMS I installed in my now-departed E36 328i. You can also view my preliminary comments for the major differences between the two systems. The Hella TC-400 and replacement pressure transmitters are available for purchase from The Tire Rack and at Bavarian Autosport.

For those of you who have an E36, most of the previous how-to still applies. I used the factory telephone connector in the E46 center console for constant and switched power and ground, but you E36ers with pre-wiring for phones should still be able to use your telephone connector, too. I'm not sure if that connector includes constant power. The part number for the E36 X400 connector is in my SmarTire thread; below is a list of the extra stuff I sourced for the E46 installation.

As always, feel free to install the system as you see fit; this is simply the way I chose to perform a clean, completely reversible installation in my 330i. I am neither a BMW technician nor a professional mechanic, and I take no responsibility for injury or damage that may result from your installation, use, or misuse of the system.


Parts

• Hella TC-400 kit, including four transmitters, display, receiver, wiring, and mounting parts
• 18-pin connector for E46 phone harness: BMW P/N 61 13 8 364 645
• Cover for connector: BMW P/N 61 13 8 364 655
• Male pin crimped to about 12" of 22-gauge wire: BMW P/N 61 13 0 005 198
• Littelfuse inline fuse holder with 5A Mini fuse
• Apollo Laser Printer Transparency Film (see Operation section below)
• Assorted fasteners and tools

(Special thanks to Terry Kennedy for posting the BMW part numbers for the connector and pins.)


Transmitter Installation

Be sure to have a qualified shop install these transmitters. The valve stems and caps are made of aluminum, so the shop will have to use special nickel-plated valve cores instead of the regular brass ones. The brass valve cores will seize in the aluminum stems.

Make sure the shop pays attention to the labeling on the transmitters. Each is labeled according to where it should go (left rear, right front, etc.). This is what you'll see when the transmitters are installed:




Wiring

There are two wire harnesses that plug into the TC-400 receiver: the power harness, which has constant and switched 12V power and ground, and the harness that leads to the display. A short antenna also plugs into the receiver. To get to the telephone wire harness in the center console, you'll have to remove the decorative trim around the shifter, the cupholders/coin holder, the emergency brake boot, and the center console. Do a Google search and you'll find plenty of DIY write-ups showing how to remove them.

Use a voltmeter to look for power and ground in the factory phone harness (below) before you insert the pins into your power harness connector. You can slide the factory connector apart for easier access to the pins for testing.



Since you're working with a constant power connection, you should disconnect the battery while you make your connections, just to be on the safe side.

My husband (screen name Doctor Wha) and his soldering skills helped me assemble the power harness. The Hella kit includes a rather large fuse holder, with 12-gauge wires coming out of it, that you're supposed to splice into the red (constant power) 22-gauge wire of the power harness. Instead, I used an extra Littelfuse inline Mini fuse holder that was left over from my SmarTire install. It's a better fit. Doctor Wha spliced the wires of the power harness to the BMW wires with male pins crimped to them. The pins click neatly into the 18-pin telephone connector. The cover slides over the connector and locks into place. Fit your power harness to the factory connector in the car, then rotate the little lever on the factory connector 90 degrees to lock it.

Check the pin location before you insert it into the connector. If you make a mistake, you can depress the little metal locking tab on the pin and pull it out.





Check the system before you mount the receiver. Connect the display, antenna wire, and power harness to the receiver. Put the key in the ignition and turn it to the accessory position. The display should light up and you should hear a beep from the receiver. If not, check your connections.


Receiver and Display Installation

You should be able to hide the receiver just about anywhere in the cabin, as long as it can get a clear signal from all of the transmitters. There is a setup feature that lets you view the signal strength on the display and tells you if you need to move the receiver to a better location.

The E46 has quite a lot of stuff packed into the dash and center console. I initially mounted the receiver above the lower driver's dash trim panel, next to the gong. Hella includes double-sided tape so that you can stick the receiver to any smooth surface, and the receiver case also includes a couple of molded-in lugs that you could use to bolt it down.

After getting a lot of "loss of signal" warnings in warm and hot weather, I decided to relocate the receiver to the back of the center console, behind the armrest base and below the rear ashtray. This is where the BMW Bluetooth antenna is mounted, so this isn't a good location if you have or want to install the BMW Bluetooth kit. To make room for the receiver, I cut out a rectangular section of carpet so that the receiver sits lower on the transmission tunnel. The carpet has an extremely thick foam backing, but the carpet portion (about 1/4" thick) peels away from the foam easily. If you trim this carpet, be extremely careful not to cut any of the wires in the vicinity, and don't cut the carpet where it will be visible once you've reinstalled the center console. To make the receiver fit comfortably, I only needed to trim the carpet - not the foam underneath.

I routed the antenna along the passenger side of the console. The receiver now sits in a central location inside the car and can receive signals from all four transmitters reliably.

Here's where I first installed the receiver:


Here's the better location at the back of the center console:


We routed the power harness past the shifter, around the passenger side of the center console, and over to the driver's side through a passage forward of the heater box. Routing the harness around the driver's side of the center console would have brought the wires in contact with the coolant pipes leading to the heater core. As this was my first time taking apart the car's interior, the Bentley manual came in very handy.

The day before I installed the display, I masked off everything except the chrome bezel, scuffed up the bezel with some fine grit sandpaper, and spray-painted it satin black. The black goes better with my car's interior, which has very little chrome in it.



The TC-400 display comes with a metal mounting bracket. I bent the bracket slightly and attached it to the steering column cover, routing the display wire harness inside the cover and down to the receiver below. The bracket is currently sitting on a couple of washers that elevate the display about 1/4" above the steering column, but it's blocking the time display on the instrument cluster. I will probably adjust that a bit or learn to live without the clock. You could also put the display into the ashtray or the storage bin below the HVAC controls, but I wanted to put the display where I could view it easily without diverting my eyes too far from the road. The steering column cover is fairly inexpensive to replace (about $20) if you ever decide to remove the Hella hardware.






Operation

One really neat feature of the Hella system is that you can choose from seven display colors. As you can see, orange is a very close match to the stock amber lighting. There are two stages of warnings: the first occurs when a tire loses 25% of its pressure, and the second occurs when the tire has lost 50% of its pressure. The display flashes yellow, and a beep sounds; you can have the display flash red/orange instead if you want. The SmarTire system beeps and flashes a red warning light at the top of the housing, but the light blue-green display color can't be changed.



When you press the CHECK button once, the system scrolls through each wheel position, showing each tire's temperature and pressure. You don't have to page through them like with the SmarTire system, but you can if you want to. The display goes dark after about a minute of inactivity.

The Hella system can monitor up to seven transmitters - two fronts, four rears, and the spare tire. I didn't bother to install a fifth transmitter in the spare, because I now have run-flat tires.

It seems as though the Hella system doesn't require the wheels to be spinning for the transmitters to send their signals. After buttoning everything up, I was able to program the system to memorize the standard tire pressures right there in the garage, without having to drive off to activate the transmitters. I'm not sure if that means the transmitters are constantly sending data regardless of whether the car is in motion, or the receiver is capable of "pinging" the transmitters. If the transmitters are constantly sending, then the batteries will run down quickly, or they're capable of recharging themselves when the wheels are spinning. Mounted above the pedals, the receiver gets a good signal from all four transmitters.

With the receiver mounted above the pedals, the system frequently flashed and beeped a "loss of signal" warning at me in warm and hot weather driving. After I relocated the receiver to the center console, I haven't gotten a single loss-of-signal warning.

I also seem to have misaligned the display - it's centered on the steering column, but it's not centered with respect to my seating position. It's a minor misalignment, and I probably won't bother to fix it.

The display is polarized. I didn't realize it until I drove the car while wearing my polarized sunglasses. Like the radio display in the E90 3-Series, the display's polarization is at an angle such that it is nearly unreadable to wearers of polarized sunglasses. You can tilt your head 45 degrees to the right until the display becomes visible, but that's hardly an ideal (or safe!) solution. E90 owners have purchased polarizing film overlays to make their displays readable, but I found a post on Bimmerfest stating that a sheet of optically active plastic, such as Apollo brand laser printer transparency film, would work just as well. It just so happens that I have a box of Apollo film, so I cut out a small square and took it outside to the car...and it works! I cut a piece to fit the screen and stuck it on there with a piece of tape. Best of all, I didn't have to send off for a piece of polarizing film.

All in all, I'm very pleased with the results.

[sjpgoalie]

I'm not really sure why you would do this...with run flat tires...

[ledfut]

That's one helluva write-up!!

[G. P. Burdell]

I'm not really sure why you would do this...with run flat tires...

It's good practice to pair a TPMS with run-flats. Federal law requires new cars sold with run-flats to include a TPMS.

EDIT: I think it's the tire manfuacturers and car manufacturers, not the government, who are behind this requirement.

The tires are rated by their manufacturers to travel a certain distance at a certain maximum speed at zero pressure. If/when you lose pressure in a run-flat tire, the TPMS will alert you, and you'll know how far you can drive before you have to fix or replace the tire.

That's one helluva write-up!!

Thanks!

[sjpgoalie]

Wow I didn't know it was a federal law to have TPMS with run flats.

[G. P. Burdell]

Wow I didn't know it was a federal law to have TPMS with run flats.

In doing some more reading, I think I may have misspoken in my earlier post. The run-flat/TPMS requirement may have been imposed by the auto and run-flat tire manufacturers, not the government. The government has mandated that all new cars have TPMS, regardless of whether they have run-flats or conventional tires.

[G. P. Burdell]

Here's how KrisL installed the same system in his 330i:

http://www.bimmerfest.com/forums/sho...d.php?t=212146

[runnr548]

Sweet stuff! Probably not for me, but a nice addition.

[smokentitan]

I'm more than likely going to get this same system. I saved some $$ on my rear tires (guy off of ebay bought the wrong size), so I might as well put it back into the car. This would be a peace of mind thing for me as I'm always wondering about inflation. Having Nitrogen available to me at work for free helps, but still. I'd also enjoy this at auto-x...

Nice write-up. Not so sure I want it on my steering column though, I'd probably put it in the glove box like ChrisL did, or the rear ash-trey if it will fit...

[G. P. Burdell]

Not so sure I want it on my steering column though, I'd probably put it in the glove box like ChrisL did, or the rear ash-trey if it will fit...

I think it should fit into the rear ashtray, but it might be a bit difficult to read.

If you put it into the front ashtray, you would be able to conceal it by closing the cover.

[TheBarvarian]

Very nice install.

[G. P. Burdell]

Update:

I got a sheet metal screw in the right front tire this week. Doctor Wha noticed it last night. The TPMS showed a normal tire pressure, so the puncture was very recent. It looked repairable, so we made it to Butler Tire just before closing time. BimmerDawg's crew patched the tire and had us on our way before we had the chance to sit down in the waiting area.

The system continues to "lose" one or more pressure transmitters every so often. The receiver usually "finds" the transmitter within a minute after it sounds the warning. I think I will relocate the receiver to behind the glovebox (where KrisL from Bimmerfest placed his) or somewhere in the center console and see if the reception improves.

EDIT: After moving the receiver to the center console, the reception is much better.

Lastly, I compared the TPMS' pressure readings to our new Longacre tire gauge. The TPMS transmitters consistently read about 1.5 psi lower than the Longacre gauge.

[G. P. Burdell]

Update: http://www.bimmerfest.com/forums/sho...d.php?t=231924

[oris642]

G.P.: Can you give me the dimensions of the display unit? Nobody seems to have that info on line. (I'm trying to see if I can hide it inside an ashtray).

Thanks kindly,

Eric

[G. P. Burdell]

I'll see if I can measure it for you tonight.

[oris642]

Does anybody else have the dimensions of the dash unit? I need to decide whether to order the Hella or the Orange (both sold by Tire Rack).

Thanks in Advance,

Eric

[G. P. Burdell]

Does anybody else have the dimensions of the dash unit? I need to decide whether to order the Hella or the Orange (both sold by Tire Rack).

The display measures approximately 4" W x 1-5/8" H x 3/4" D. Sorry for the late reply.

[oris642]

Thank you!

For the record, the Orange unit that is also sold by Tire Rack is 3.25" x just under 2".

[bong bong]

G.P. Burdell,

Great write up. I decided to do the same install.

Do I use phone harness to tap the all 3 connections required? -- switched, ground, and the contant power?

If so, I suppose I will need to get 3 of the male pins (BMW P/N 61 13 0 005 198); is this correct?

[G. P. Burdell]

Do I use phone harness to tap the all 3 connections required? -- switched, ground, and the contant power?

If so, I suppose I will need to get 3 of the male pins (BMW P/N 61 13 0 005 198); is this correct?

Thanks for the compliment. Yes, I believe I used the telephone harness for constant power, switched power, and ground. The wiring scheme may vary between model years, so test carefully before you insert the pins.

Yes, you'll need three of the male pins. Get extras in case something silly happens.

[bong bong]

Great, thank you!

[bong bong]

I had the Hella TPMS sensors installed with a new full set of tires about 3 weeks ago.

I installed the monitor inside the front ashtray. To do this, I removed the ashtray container and the push clip behind it. It fitted perfectly without any modifications. The compartment even has a hole underneath for the wires to run through so I did not have to drill.

Attached is a picture where I used a prong picker to pull the wire through so I did not have to dissemble the center console. Also attached is a picture what the connecting wires look like.

I found that the in-line 5A fuse is not necessary because the phone wiring harness already has a 5A mini-fuse. And the phone harness supplied the ground, switched and constant 12V required. The receiver went underneath the front passenger footwall, which gave me 3 full bar signal strength.

G.P. Burnell, again thank you for helping me out.

[G. P. Burdell]

Update:

The system works perfectly for me now that I've moved the receiver to the back of the center console. Having the receiver above the pedals must have put it too far forward to get signals from all four transmitters reliably. I've edited the first post accordingly.

[Hdhntr23]

G.P.

New member here and I think this is my first post but Im a regular at the M5board.

Anyway I came upon this thread thru a search and Im curious if you wouldnt mind answering a couple of questions.

First, which phone harness did you tap into? Mine is prewired for a phone, I have the snap in in my arm rest and I have BlueTooth retro fitted. Ive wired my Hella to my garage door opener wires but your install looks a lot cleaner.

Next, when I start my car it goes thru the check for all 4 tires then it flashes the circle on the right for awhile then it goes blank. Is this normal operation?

TIA. Im sure Ill have more questions but thats it for now.

Oh and thanks for taking the time to do this write up!

[G. P. Burdell]

First, which phone harness did you tap into? Mine is prewired for a phone, I have the snap in in my arm rest and I have BlueTooth retro fitted. Ive wired my Hella to my garage door opener wires but your install looks a lot cleaner.

In the E46, there is only one telephone harness underneath the center console. The Bluetooth pairing button connector plugs into this harness. I do not have any experience with 5-series vehicles, so you will want to check the Bentley manual wiring diagrams or consult people more knowledgeable than me.

Next, when I start my car it goes thru the check for all 4 tires then it flashes the circle on the right for awhile then it goes blank. Is this normal operation?

My system does not flash the circle on the right. Check the instruction manual.