Hi all!

I have a 2004 HCH with 98,000 miles on it. Started getting the IMA light and CEL, but they were intermittent. Finally got them fully on. Removed the battery pack and did a fully discharge/recharge conditioning. That cleared some error codes, but the IMA/CEL still on. Decided to take to the Honda dealer, and they are telling me "P1637 MCM internal circuit failure. Software is up to date, need to substitute/replace MCM and recheck condition".
I have searched a ton on YouTube, and here (and the Civic Forums) and cannot find exact where the MCM is. The guy from Weber State University on YouTube has stupendously good videos ( ) but somehow, despite incredible detail on almost every other part of the hybrid system manages to miss talking about the MCM.

Where EXACTLY is the MCM?

If anyone knows of a video where it is replaced, could you point me to it, please?

If I buy one on eBay, I want to make sure I get the EXACT right part. Thoughts?

Many thanks!

 

Update: I found the YouTube video from the amazing guy at Weber Auto that describes where the MCM actually is!


When I look on eBay, places like Hybrid Battery World have an MCM for $25 (https://www.ebay.com/itm/314397483567) and the same thing for $60 (https://www.ebay.com/itm/314624846378). What do I need to know here for why one is $25 and the other $60

There's also one listed for $85 (https://www.ebay.com/itm/233023538679) which came is "Removed from 2004 Honda Civic hybrid. Fits the following models. 04-05 civic hybrid mx w. Manual transmission, California emissions. Dealer programming required"

As already stated, I have a 2004 HCH with manual transmission, so I am leading towards this $85 one, but is there really a difference between these MCMs for the automatic vs. manual? I can sort of see why there might be.

Thank you!

 

I had p1637 and p1600, replaced ecu and it fixed everything. Its behind the back seat right next to the battery. People are calling it an MCM but it is really called an ecu. Costs around $200 rebuilt from greentec. There is no difference between the ecu for auto vs manual. And also dont worry if the serial number/model number doesnt match up, it should still work fine. Don't worry about programming it, it doesn't need to be programmed.

Originally I bought a rebuilt battery from greentec and installed that, and didn't fix anything, car didn't even recognize it. Turns out the ecu was actually the problem and I probably didn't even need a new battery. I plan on keeping the car for a while so I kept the new battery anyway.




https://www.greentecauto.com/hybrid-...2003-2005-ecu/