'02 Millenia S, started idling a little rough, exhaust smelled rich, and CEL lit. OBD2 reader showed generic P0105 code. I tested the MAP and MAP solenoid - both seemed to pass vacuum and voltage tests. Hoses that aren't buried look fine. The one plastic tee I was able to check is also good. Car has very low miles, so hoses look almost new. I tried but failed at removing the supercharger air intake pipe. Ran into a few clips I couldn't manage to release, back by the firewall, so I couldn't get to the buried hoses. Anyway, I checked and cleaned every wiring harness I thought might be related, cleaned the MAF sensor, and put everything back together. Cleared the error code and started the car. The P0105 was gone, replaced by Mazda-specific P1601 (Powertrain Control Module Communication Line to TCM error). I might have a chance at diagnosing this, if I could figure out where those two items are. Anybody have decent diagrams to show their locations? Or maybe an idea about fixing the problem?

 

Not sure why you thought either was generic... but moving on..

The next DTCs based on the *limited information you posted about your Mazda the suspect may be as simple as dirty connectors. But you may also be looking at replacing your ECU?

I would also suggest that you take a peek at the monitors and see if any are in fault? This really is always a mystery area on all forums with DIY using (low quality none shop) scanning equipment (blue tooth scan tools generally really suck) (it is always better to connect directly to the ODBII diagnostic connector) yet vital to knowing how and what plan of action may be needed to resolve DTC's and other issues.


* Think of this another way... when you go to any service shop dealership or independent what are the information that is required on the service write up?

 

Two reasons I thought the P0105 was a generic error:
1. When I looked up that error, I found no less than 10 possible problems related to that error code, and I thought, "Wow, that's pretty generic."
2. When the code appeared on the scanner, it LITERALLY said, "Generic" on the screen.

Hope that eliminated your confusion.

Now, for my own confusion: Not sure what you meant by "take a peek at the monitors..." I'm also unsure about what other info I should have included about my car. What else would be helpful in diagnosing the problem? As for dirty connectors, I inspected all I could find, and despite them looking pretty spotless, I cleaned them all anyway.

 

When in the future looking up ECU trouble codes use the vehicle type, in this case look up the DTC that Mazda uses. So the PO105 is not a generic code but sensor conditional. This is also why it is always better to use a Diagnostic Scanner that is close to a professional grade and not blue tooth or ebay, amazon or estay cheapies!

P0105 Mazda Code - Manifold Absolute Pressure Sensor Signal Out of Range

• Faulty Manifold Absolute Pressure (MAP) Sensor
• Manifold Absolute Pressure Sensor harness is open or shorted
• Manifold Absolute Pressure Sensor circuit poor electrical connection
• Faulty Engine Control Module (ECM)

The monitors show the condition of the emission related systems and component. Generally, if any one or more sensors is a problem it will show the monitors as not in readiness. This means that your engine may be producing higher emission at the tail pipe which is also an indicator of a faulty sensor, connection or ECU problem?
The best advice is NOT to randomly start to change parts but use the proper problem-solving tree and check each part in order some order recommend by the Factory service guide or a program like ALLData. Changing untested parts for failure can cause additional problems to your current unresolved problem.


Example of a Generic code:
P0300 is a generic OBDII code that can occur with the Mazda......................

 

Thanks, Callisto, that was some very helpful info! The scanner I used was an AD310, a loaner from my neighbor (a mechanic). I know they're not as thorough as what shops use, but it's what was available. Not sure why the display labeled the P0105 "generic," but it did. When I used the word "generic," it was more to describe the fact that there were multiple possible problems that would throw the code.

Anyhow, I'm now dealing with the P1601 code, after all of my efforts. Haven't seen the P0105 return yet, so maybe my cleaning efforts worked on the MAP sensor. No idea. The reason I'm trying so hard to diagnose the trouble myself is to avoid replacing expensive parts needlessly.
Thanks for your help so far, I really appreciate it.

 

Ok understand. Some older Scanners don't use specific manufacture for their exact code meaning. Mine does. But also cost several thousand dollars.

See if the loaner has an area called CHECK MONITOR STATUS

As for the other DTC my guess is all your attempts may have simply caused a condition that is fooling the ECU that the TCM has a problem. It happens sometimes. So if you first tried to reset the DTC and reset the monitors BOTH then drive it for at least 1-3 complete drive cycles. Or disconnect the battery for 5 minutes and reconnect it. This is a DIY method and may still not clear the permanent DTC file but theoretically keep your DASH Check engine light off for a couple days so it won't drive you crazy, that should be enough time for the ECU to see that the TCM is communicating and will remove the ECU file holding that trouble code as active.
I would sign off with my ASE but because i suggested the battery disconnect I can't. I often tell people not to do that just to clear their dash engine check light. So I guess my response this time is a DIY.... LOL

 

Thanks again for even more helpful and appreciated pointers, Callisto. I reset the DTC, but I'm still fuzzy on the "monitors" thing, or how to reset them. I haven't yet checked the scanner for the option you mentioned - will do that shortly. I'm currently looking to see if I can find info on the Milly's drive cycle requirements. I'm planning on replacing the Miller Cycle cover and taking it for a drive, with my fingers crossed.

 

A single drive cycle is the engine completely cold started and drive no less then 30 minutes constant driving. Most OBDII from about 2014 to present actually to complete the ECU sequence in drive cycle is from 3-5 drive cycles.
Contrary to the debate mechanic often have it is easy to check if the ECU has cycled enough drive cycles to clear all pending actions as well re-set the monitors and clear the permeant files having to do with anomalies and hard operating issues.

The monitors will general be in the operating index of the scanning tool being used.
If it is not there then it is easy to old or a cheap scanning tool. LOL

 

More thanks for the info. I just completed the Drive Mode 1 test that I found here on the forum. Prior to the test, I cleared DTC's. Fired up the engine and did the increasing RPM tests. The P1601 is now gone, and the P0105 is back. I saved pics of the test results, in case I have to give up and have a shop investigate. I'm a novice, when it comes to OIBD2 scanners and what they tell you (in case you hadn't figured that out already) ;-)

Is it safe to drive the car at highway speed to attempt the remaining Drive Mode tests? CEL is steady, not blinking.

I couldn't find a "Check Monitor Status" menu item on the scanner.

 

The reason it returned honestly is because you followed bad advise. Sorry! No offence and I understand the WWW in thinking all the answer are easy to be found and quick to resolve. If it were that simple I would have to work in a shop anymore everyone one be expert DIY. I read this happening every day on the internet and on various vehicle forums.
You can drive it is just an annoying engine check light. It is when the RED light comes on that you are in trouble.
But I would maybe go re-read what I have posted and try to follow it.
The events causing the DTC to have not yet been solved. So, when you "reset" by way of only turning off the dash check engine light the ECU is still basically waiting for (joke not AI lol) you to solve the original issue, so to say.
I am still suggesting that you get a look at the monitors.


ASE