2011 ma,da 6, failed smog test. Nothing wrong with the OBD2 diagnostic, but my mechanics testing machine was being locked out. Is this a known fault or could it be a miscommunication between the ECM and his test machine.

 

You are not providing enough information... First what state do you reside in.
What you posted is conflicting information about what happened

 

Welcome to the forum

 

The OBDII diagnostic connect and the use of emission certified and state registered testing machine act first like a Diagnostic scanner. So, when it is connected to the OBDII connector it will basically see the same information a handle held professional scanner. This means that it can see min. 3 basic areas of the ECU. Current DTC, pending DTC and the most important when it comes to emission reporting the state of the I/M monitors. If the service shop is not seeing these then it is the shops machine of the operator that may be at fault. It's easy to test simply connect a professional handheld even semiprofessional just good quality diagnostic scanner into the OBDII diagnostic connector and look in at least the I/M monitors? NO BLUE TOOTH scanning devices!!!!!

The other which you hope did not happen is your OBDII diagnostic connector was damage by someone not correctly connecting any devise into your connector. Taking a flashlight generally you can see if that happened?

If you live in CA then I have more information.

 

The information is indeed puzzling. This is in California. The OBD2 code reader shows no faults, but when connected to the smog test machine my mechanic says he is being locked out. He is a very good mechanic. He suspect he might have a problem with testing machine. This is a 2011 Mazda 6 with a 2.5L 16 valve. Could this be a known fault, or is it likely he may need maintenance on his tester.

 

Something to know because you are in CA. First assuming that your OBDII connector was not damaged....and during shops set-up that your vehicle was not already registered with the CARB with his emissions equipment. If it were and the report shows testing fail or incomplete test you may now be required to go to a Calif Emission testing facility and may no longer be able to use an independent emission privately owned smog shop/business. The tester should have told you one way or another to at least reassured you that your Mazda was not already in the system for CA from his shop. The service shop or emission facility you went to either having a certified for current regulation and license requirements to perform emission testing and as such have any issue with the required emission testing equipment must be reported to the state of Ca and you would think that shop would also contact their equipment service rep to inspect their machine before doing any more emission testing.
I suggest as I did in the other responses is scan your ECU and look specifically in the *I/M monitors. If they all show in readiness and no *permanent DTC that are cycling then your emission test will pass that portion of the test and hopefully you don't have for the visual inspection anything unusual under your hood or under the Mazda that is not within allowable service repair of parts or added items not C.A.R.B. approved.
On a side note and not to evade Ca but I would based on only what you said in your first unedited response choose a different emission testing service shop and not return to the one that had the issues.

 

My mechanic didnt have the time to diagnose the problem. (He's a one man operation). He suggested a different shop. The other shop found the clips in the socket were corroded. This is what caused the failure. This explains why the scan tool worked but the tester didn't. Scan tools are used often keeping the blades clean. Testers are used less often. Probable minor mismatch in the pickup. The second shop wanted to depin the socket and clean the clips. I declined. I bought a cheap nail file and cut it down to fit in the slots. The file cleaned the corrosion. The test was successful. And I saved myself an additional $125.00. Cost $1.25. All's well.

 

interesting assumptions and findings ..... corrosion????
The bottom line is somebody screwed up your OBDII diagnostics connector. As for an OBD connector getting dirty... well even without the cover I can say its almost statistically not even a consideration for them getting dirty to the point when a scan tool is connected would not make a connection to the ECU. The exception would be a water damage and then how did the water get under the dash area? Then you may have gotten corrosion ??? But if that were the case you might expect in the future other electrical mysteries happening. At least you can suggest to the next shop if that happens about your OBD connector. Not telling them could cost you more with them looking for a new electrical problem.?

Glad you are getting it taken care of. Also, that you did not go for the cleaning service of 125 bucks. Wow someone(shop) is giving service shop a bad reputation. A can or CRC electrical parts clean sprayed into the connector would have clean them just fine and you could DIY!

BTW It is a professional practice from qualified service mechanics or auto techs that when you can't connect to the ECU/PCM then you look to make sure none of the connector pin are bent.