jscott82

Working on the wiring harness for my spec Cayman. Ive been chasing an ECU error, "U0146 Communication Gateway (CAN Drive)" for days.... Then today out of frustration I put the HVAC module back in the car and the ecu error goes away... This makes no sense to me, the ECU is on the "DRIVE" CAN buss, the HVAC is on the "COMFORT" Buss.

Anyone seen this before?? At this point I assume it's an erroneous errror, everything seems to work fine. I assume the ECU is making a call to the HVAC that is failing, and it just assumes it's a buss issue..

TXE36

Wild guess: The ECU needs contact with the HVAC module to track if the ac compressor is on?

-Mike

dgmark

The gateway module controls the power up functions for various modules. The gateway module is looking for the AC control module to power it up, It is not seeing it and setting the code, You can configure the gateway to set for no AC but it is tricky as there may be unintended consequences. I saw the same issues with the Spec Cayman that I built, You wont have any problums.

jscott82

Thanks

And ya, that's the issue, I have the gateway coded correctly (I think) it's reporting no errors. It's the Ecu that say it has a buss issue.

Glad to hear I'm not the first to have this problem.

jscott82

You are right, it does need to talk to the compressor and throws another error complaining about that. That I expect.

It's the buss error I'm surprised by as they are on separate busses. The gateway connects/translates between them and it is not reporting a problem.

MRW

Not sure what the final consequence of what you're doing is, but might want to think about retaining windshield defog capability. Comes in handy on those cool rainy days.

jscott82

Yup!

I plan on retaining the defog ducting, but using a simplified fan/heater, rather than the complex factory HVAC.

cosm3os

Rag-on-a-Stick!

Frank 993 C4S

If you want to go ultra light weight think about going with an electric heated windshield which is in essence rear defogger elements attached to the inside. This only works with glass. It is available from Bimmerworld for about $100. I had an excellent experience with it for two seasons but you have to feel comfortable looking through the heating elements. It can be distracting for some.

TXE36

A tiny drop of Dawn dish soap applied with a dry paper towel to a dry inside windshield. Schmear on the inside glass and rub until clear. One drop per side - will last all day:


Note the side window w/o treatment. No blower no nothing. I've tried the rag on a stick - it's overrated.

-Mike

38D

I'm right in the middle of the same project. Really hoping I didn't screw anything up!

dgmark

If you remove the AC control head you have to install a power circuit for the rear defogger as it is a can buss signal to the BCM from the switch to actuate the defogger. For the front defogger we installed a really trick heated front glass out of England the grid lines are nearly invisible. Defog for the front and rear glass is actuated off a 10 minute timer.

cmac

'Tis the season, I guess... Planning to do mine in about 2 weeks. Any suggestions on an electric heater/blower? I've got a Lexan windshield, so the other solutions aside from rag-on-stick are out.

jscott82

For the comfort buss(would not try it on DRIVE) there are some pretty trick programmable CAN controllers out the to inject the triggers for things like defoggers,. Mirror controls etc...

I haven't got that far yet.. it is certainly an adventure.

dgmark

The triggers for the can bus functions are the easy part. What is hard is picking out what the hex code that is used for a particular function. I have used an Adrino board to sniff comfort bus but have not had any luck so far. I need an embedded code programmer to get on this with me. One project that I want to accomplish is use the Sport-Crono as a stop watch to time pit stops.