Long story short: I have a 2003 HCH with a CVT tranny and about 80k miles on it. The IMA system has stopped working and the 12v charging system only works at RPMs above 2000. In addition to the 12v light being on at low RPMs, the CEL and SRS lights are on. When I start the car, it hesitates to turn over and then sounds different (is there a backup starter to the IMA system?). I took it to Autozone and downloaded the code P1639. This appears to be "MOTB signal circuit malfunction". Anyone know what that is? I'm guessing that the controller for the IMA system is having problems and isn't allowing the IMA system to work or charge the 12v system. Any ideas on how to perform a more indepth analysis?

 

Here's a follow-up to my issue, just in case anyone is interested. I'm still in the middle of it, but... The P1639 (or U0110 in some models) code denotes a signal malfunction between the engine control module (ECM) and the motor control module (MCM). The repair manual has you check for a wire short or open circuit. Of course, that wasn't the case for me. The next step is to replace the MCM with a known working unit. They are at least $1600.
I took the car in to the dealer to double-check my work and to see if they could test it out with a "known working" MCM. They agreed that it appeared to be the MCM, but didn't have one around to test. They gave an estimate of $2400 to replace the MCM. I took it home and ordered an MCM from ebay ($119). I installed it and... it didn't solve the problem. So either the MCM I bought has the same problem (highly unlikely) or the problem lies elsewhere. At this point the next (and last) step in the manual says to replace the ECM. It's only about $600 new. Luckily the guy I bought the MCM from has an ECM for about the same price and is willing to exchange. It should be here in a couple of days. Fingers are firmly crossed....

 

What was the outcome?

 

Ahhh, the outcome... So it turns out it wasn't any of those things. Somehow a fuse was missing. Elves... or maybe fairies. If anyone lives in the Portland, OR area and has a problem with a HCH IMA, try Bumblebee batteries. They're much more knowledgeable (and reasonable) than the dealers (and they know the ways of Elves).

 

Wow. Thanks for the follow-up.

Eli is good people.

 

Hello rob
I know this is an old post but i hope you see this
I have the same problem and i have the same code showing
Do you remember in which fuse box the missing fuse is, and if know wich fuse was i'll thankful
Thanks in advance

 

Ohh, that was a long time ago. It was in the main fuse box inside the car. To the left of the driver. I can’t recall which fuse it was. Good Luck