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Discussion Starter · #1 ·
First a little background on this car.. It is a 2006 MDX with 130K. I just replaced the engine myself with a new/used 70K engine because the original engine had a burned valve and the rings had been bad for a couple of years. It burned a quart of oil a week.

The new engine went in fine but came with it's own wiring harness and all sensors attached so I just left all that on there and plugged it in to the ECU.

Now I have a hard code P2649 and it won't rev above 3500 rpms. It runs excellent other than that. I had neither of these codes before the engine change.

OK, no problem I thought, it must have a bad VTEC oil pressure sensor so I swapped it out with the one that had been on my original engine. No change. So I swapped the VTEC solenoid and the OP switch while I'm in there.... no change. Great. So then I pulled off the VTEC solenoid casting and cleaned the screen, nope, not dirty. Yes, I have new 5W-20 oil in it with a new oil filter.

So now this little bug is getting nasty...darn it. Off to YouTube- I looked at a bunch of stuff and then found this by KY garage- excellent info: YouTube- PHgsFZYXevw

I metered out the wiring to the VTEC OP sensor and got nothing on the power side and no ground either so I figured the harness that came on the new engine was bad. So I probed the harness from the ECU connector to the switch (BLU/BLK wire) - nothing. Cool. I spliced into the harness wire just out of the ECU connector and ran a new wire to the plug at the switch and a new ground on the BRN/YEL wire and figured I had it nailed. No...... freaking really? No.

So where I'm at today is I probed for voltage at the BLU/BLK power wire and it is showing me 6.94 volts with the switch plug off, yes, not 12V. The P2649 code is a hard code that will not reset - ever. I clear it on my scanner even with KOEO and it just pops back on. How can this be setting this "High" code with the VTEC OP switch either connected or disconnected with the KOEO? I have much lower voltage than I should on the BLU/BLK wire straight out of the ECU. (Yes, I have 12V at the batt)

Do I have a bad ECU?
 

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Discussion Starter · #2 ·
I know, long post but I wanted to get everything in so not to waste your time answering things that should be in the post to begin with. A little bit more - I had no ECU issues before the engine swap. I disconnected the battery at the start of the project so shouldn't have got any random voltage spikes through the ECU to fry it. I don't really want to change the engine harness unless there is a relative reason, but I will if needed, it's just a PITA and the top of the engine has to come off to do the FI stuff and the trans wiring is also a pain when everything is now back together.

I know there has to be some really good techs here that can help me figure this out. Help.
 

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Discussion Starter · #4 ·
I'm using the Torque app on a smart phone. It is "supposed" to be HDS compatible and so far it has worked great. Not saying it isn't failing here though... Give me a little while to go through this troubleshooting info and I'll get back to you. THANK YOU for the reply and info!
 

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Discussion Starter · #5 ·
OK. I have no continuity on the solenoid wire from the ECU plug to the solenoid plug. I think I'm going to jump that wire and do a retest to see if the ECU will reset. I believe that wire is a GRN/YEL and runs straight to the ECU from the plug?
 

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Discussion Starter · #6 ·
I jumped out the OEM wire like I said above. All fixed!! I will now loom everything back up nice and sweet. The hard code cleared itself before I could even get the scanner on it. I checked the codes, all clear. It's out of Limp mode and now revs free. I can not say thank you enough! Thank you! Hope this post helps guide someone else to a solution also.
 

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I LOVE a happy ending.

The Torque app is great, but won't do everything the HDS will (by a long shot). It will clear most codes though, and the ability to put together a unique "dashboard" for each troubleshooting opportunity makes it (IMHO) one of the top must-have tools (assuming you have a 'droid phone - iPhones have to settle for lesser apps that cost more). HDS clones are pretty much necessary for really "getting under the hood" of Honda vehicles - well worth having if you are going to have a Honda / Acura vehicle for a while.
 

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Discussion Starter · #8 ·
Drove the car, all is well!

I do like the Torque app. I wish it was 2 way command/control. I like that I can build a list of inputs and assign various gauges. It's really nice to be able to watch the gauges in real-time on a test drive. Heck, there doesn't even have to be anything wrong with the car! Maybe I just want to watch a vacuum gauge and O2 sensor reading sometimes. I guess I'm just geeky that way :) I jumped from a HTC to an IPhone about a year ago so I ended up with a smart phone I wasn't using. I bought the Torque app and a transmitter for the OBD-II port and love it. Because it's wireless I can have the car running and be going over stuff in the app sitting 20 feet away at my bench. Pretty cool.
 
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