MS3 PCM fault?

Tyler Young

Tyler Young

The road to hell is paved with tread tracks
Greenie N00B Member
Greenie Member
So I bought a 2012 about 9 months ago from a dealer, 1 previous owner. What they failed to tell me was how much he actually done to this thing. I apologise for how lengthy this post will be but I've been having hell ting to figure out what the hell is going on. This is everything I've stumbled upon so far...
Front mount intercooler swap
aftermarket turbo (unable to read name plate)
cold air k&n 3" intake
Not the stock battery (although I assume he thought the sub in the truck might have something to do with that)
EGR delete
Aftermarket intake manifold (no name plate but it doesn't have the.. I forget what it's actually called but it's like a secondary throttle body for each intake channel) idk
Radium pcv baffle plate with loose hose INOT CONNECTED TO INTAKE MANIFOLD, intake manifold pcv is plugged ( I assume he had an occ and cut it off when he traded it in... Idk)
The PCM is no longer mounted to the battery bay, I guess to allow room for the intake.

So far, that's everything I've encountered. Now, for the real fun. For the past few weeks I've been chasing an electrical fault/ghost vacuum leak that, at any given time, causes my ms3 to read full boost, then drop into limp mode. At first I could just perform a hard reset and it would clear the codes and be fine for a little while but it's been getting worse, been stranded for an hour or better just reseting my computer hoping it will start up and run correctly. I've replaced MAP, MAF and Wastegate actuator solenoid, i checked for vacuum leaks every way I know how and it's still getting worse. Got a buddy that works for Mazda that came over and checked it out with me. Got it to fault, read codes p0069, map/baro, along with bank 1 too rich. We believe the PCM is to blame, also don't believe this first owner even had it tuned after he modded the hell out of it.. what do y'all think? I love this car, I want to fix it..
 
Post tons of pics. I'm betting stuff is not set up properly.

Got an AP or Versatuner?
 
Sadly no. I've had my eye on the cobb access port for a while but I don't make hella bread

Anything else I'll have to take the intake out and unless absolutely necessary, it's a pain in the ass to get seated back correctly

15942484426404094831291862114520.jpg 15942484780419145431718705248669.jpg 15942485067566819601017251191020.jpg 15942485660842313256710913229022.jpg 15942485938713132884180102884903.jpg

That and if there was a tune on this, how would I be able to find out?
 
Last edited by a moderator:
I am so sorry you inherited such a project. The intake manifold is a ported stock manifold, hence why you do not have the butterfly valves.

The intercooler could be a CPe kit.

You intake is more than likely an HTP intake.

If you had a flash tuner like the Cobb AP or Versatuner, then for sure you would have a tune. Without one, its possible that you might not. Although there are dumbasses that unplug the AP and trade the car with a tune on it.

I would check the ECU wiring harness to make sure it didnt rub on anything since its just dangling like a limp dick. Also check the MAF harness, that might have a kink or break where it meets the rest of the ECU harness.

The map and baro thing could be from an aftermarket sensor on stock tune, or vice versa since you said you replaced it already. Also if you dont have a tune, you will throw a code with any intake other than stock.

Your BPV should also be recirculated into the intake, but some HTP ones dont have the BPV inlet for the few guys that run the BPV vent to atmosphere (or VTA).

Your PCV plate may have a hose leading to a catch can, which may have a VTA filter. That would explain the plug on the intake manifold. This would also throw a code if not tuned for the extra bit of air that comes through the filter.

When you replaced the MAP and MAF, did you buy OEM sensors or aftermarket?

I wish i could be of more help, but that car is a clusterfuck of poor modifying.
 
As far as the map sensor I bought a corksport 3.5. it's the 1 that was in there when I bought this. The MAF is AutoZone special (oem) and the Wastegate solenoid should be oem as well. This is the hose hanging off the radium baffle plate I think he had a can before, then cut it off, or it dropped out, idk

IMG_20200217_175939.jpg IMG_20200216_174400_01.jpg

The only thing that confused me is the boost gauge shows a constant vacuum leak. That's where I started this Scooby Doo shit show

Would a new PCM likely solve what's going on?
 
Last edited by a moderator:
That hose is where the Pcv should be, but it's not. There needs to be a Pcv or occ from the Radium plate to the intake manifold, it can't be open like that taped up mess.
 
Correct, but from research I've been doing since it's more so just a vent for the crankcase that just feeds the vapors back into the combustion process, it's messy but I don't think it's contributing to the issues I'm having. Least I don't think it is, idk. This is my newest, first boosted car
 
Step 1.... The BPV should be clocked a little, then get a hose on the intake and plug that back in. I doubt you have a tune for VTA, given that ratty ass engine bay.

Figure out a solution to the PCV system. The PCV plate should be run back to the intake manifold plug BUT only after you throw a PCV valve back on. Otherwise get a VTA catch can, and a tune for it to match.

Fix any damn oil leak you might have, if you havent already.

That MAF sensor may be what Autozone matched, but our ECU has a history of not working well with aftermarket sensors. HOWEVER i wouldnt worry about that now.

You may have leaks at the intake NPT fittings, and leaks at the throttle body and manifold gaskets. Make that step 2.

Step 3 would be checking the couplers and tbolt clamps.

Here is where your BPV should be connected.

20200708_213513.jpg
 
Last edited by a moderator:
Think I might get a catch can honestly. Last thing I need is oil caked lifters. But I think I'll reconnect the bov and see if I like it better, I've read it improves performance and shifting lag. But what do you mean by clocking in the bov? My Mazda buddy also thought I had a leaky intake manifold gasket.. probably need an intake that fits a little better as well
 
Unscrew the top and rotate the recirc part to the back.

Duralast MAF is a bad idea.

3" intake I'm confident requires some tuning. I would get that under control with Versatuner or AP.
 
You need to figure out the tune situation that size intake shouldn't run without a tune so you have some work to do making sure that the tune is a good one and not some Homebrew bs that is going to blow up
 
Believe me I hate duralast. AutoZone electronics seldom work for me. It was just in a pinch cuz I was throwing codes for MAF before. Sounds like I just need to find a good tuner shop. I'll shop around for a versatune
 
Mauro_Penguin said:
Step 1.... The BPV should be clocked a little, then get a hose on the intake and plug that back in. I doubt you have a tune for VTA, given that ratty ass engine bay.

Figure out a solution to the PCV system. The PCV plate should be run back to the intake manifold plug BUT only after you throw a PCV valve back on. Otherwise get a VTA catch can, and a tune for it to match.

Fix any damn oil leak you might have, if you havent already.

That MAF sensor may be what Autozone matched, but our ECU has a history of not working well with aftermarket sensors. HOWEVER i wouldnt worry about that now.

You may have leaks at the intake NPT fittings, and leaks at the throttle body and manifold gaskets. Make that step 2.

Step 3 would be checking the couplers and tbolt clamps.
Click to expand...
The radium plate comes with a built in valve it is on there so that is working but that ghetto hose job is garbage and I would just run a new hose right to the intake for now to get rid of the leak and get a catch can at some point. I would also check what is going on with this.
upload_2020-7-9_10-38-17.png

Something sketch A/F there too.

That intake 100% needs a tune or the car will run like garbage 24/7 it is a 3" HTP
Your old maf sensor was probably fine but the mafcal was not so the car has no idea what kind of air it is getting. The issue people have with the non OEM ones are that they do not handle boost and max out way earlier than they should so your mafcal also gets out of wack and your car once again does not know how to handle fueling. In order to run this car right for any amount of time with that intake you will need to get an AP or Versatune. If you don't plan to get wild with tuning and stay within stock block range VT is fine. AP is nice to be able to see your data while doing a pull and more people support it. I prefer AP at this point but VT works for people with simpler setups and smaller budgets.

Get a bluetooth dongle and the torque app plus the mazda pids app and you can at least see what all the sensors are telling you. As far as I can tell this can mostly be fixed but it is a decent amount of shit for someone that is not experienced with these cars. So far it sounds like you are off to a good start and are doing the right things.
 
Man.. thank y'all fr. I'll update as I get shit done, kept the old MAF just in case. I needed a little help and y'all certainly have been. Now, time to stack some bread up
 
So I've got a Chromebook. Are there any trusted applications for versatune or anything else?
 
Dude, you gave me a dislike for helping you. What? I don't think dislike means what you think it means lol. Generally you do a dislike if the post was not helpful/rude.
 
You 100% need a tune, STAT, for the larger intake and the CS MAP sensor. Until that's done, you'll be chasing some phantom issues that can really only be tuned out. Remedying that will help you to begin diagnosing the rest of it.

I am also wondering, though, if it was traded in with a tune and the guy sold a married AP -- reason being that you should be seeing constant CELs at least for the EGR and VTCS being deleted; if you aren't throwing codes for those, then the car is not on the stock tune.

You might want to try getting on facebook with pics and details and see if you can track down the previous owner or someone who knows him/is familiar with the car.
 
You must log in or register to reply here.
Back
Top