Unable to complete Inspection Diagnostic?

Tiny
DAGUST482
  • MEMBER
  • 2009 MAZDA CX-7
  • 2.3L
  • 4 CYL
  • TURBO
  • 4WD
  • AUTOMATIC
  • 110,000 MILES
I went to bring my vehicle listed above for inspection. The mechanic said he was unable to connect successfully to the car computer. Said it could be problem with electrical/ECM, etc. I had recently disconnected car battery a few days ago to clear a problem with the anti-theft system. Could this have something to do with the inability for inspection tool to read computer? Short of bringing it to a Mazda dealer for an expensive diagnosis/repair, is there anything I can do to reset the ECM or check to see if there's something wrong prohibiting the inspection connection to the computer? Thanks!
Tuesday, January 3rd, 2023 AT 11:48 AM

3 Replies

Tiny
AL514
  • MECHANIC
  • 4,125 POSTS
Hello, this can happen at inspection stations sometimes due to losing connector pins or even his system at the shop. I'll look up the information data bus for your vehicle. But is it running okay, no Check engine light or any other warning lights? Try going to your local auto parts store, such as AutoZone or Advance Auto, etc. Have them scan the vehicle for codes, even if the Check engine light is not on, if they can scan the engine computer (ECM) for codes then there is communication with the ECM through the data link connector.
Another thing is that the use of some aftermarket scan tools actually has wider pins in their connectors, and they end up spreading the female pins in the data link connector in your vehicle, there was a warning out about this awhile back. Some cheap code readers were causing this. So, if the auto parts store cannot communicate with your ECM, then you'll know the issue is with your vehicle and not some other cause. I'll post the diagram for your information bus, there is a fuse you can check.

Ok after looking through all the wiring diagrams, there are some other possibilities here.
Diagrams 1 and 2 below are aftermarket diagrams showing how the communication wires are routed. In diagram 1 on the left is the Data Link connector under your dash, you can see that the highlighted wires run to the Body Control Module first and come out to run down to the engine computer and a couple other modules, so it's possible that communication was lost through the BCM, and their scanner is not reaching the ECM. In this case the BCM is a type of Gateway for those other modules. There is also a fuse you can check at the top of diagram 1.
The 3rd diagram is the OEM (manufacturer) wiring. It's the same. Just a more complicated version.
The other possibility I came across was labelled "DTC Inspection" (diagnostic trouble code inspection) According to this service information you can see in the 2nd to last diagram it required a few conditions to be met to retrieve trouble codes, which is what an inspection station is looking for, A vehicle will fail if there's any trouble codes related to emissions stored in the ECM. I'm not sure exactly if a manufacturer would require these conditions just for getting codes out of the computer, I've never heard of this before. But it is in service info for some reason. It requires all switches off except the ignition switch, all doors closed, all doors unlocked, and Parking Brake lever pulled.
Bring the vehicle to an auto parts store for a free code scan and see if any of these make a difference. Hopefully this will help. I would think that if any of the communications networks were down you would be experiencing a lot more issues. I also added the Technical Service Bulletin about the data link connector pins being spread by aftermarket devices (last diagram).
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Tuesday, January 3rd, 2023 AT 1:09 PM
Tiny
DAGUST482
  • MEMBER
  • 3 POSTS
Thank you so much for such a thorough reply. Car is running okay, no engine check light or other warning lights. I'm going to go to an auto parts store tomorrow and see if they can run a code scan.
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Tuesday, January 3rd, 2023 AT 2:54 PM
Tiny
AL514
  • MECHANIC
  • 4,125 POSTS
Okay, let us know the outcome, if we need to dig further into the body control module operation we will. Just verify that everything is working correctly, windows, door locks, etc. Tell them at the auto parts store to be easy on the data link connector. And try the list of inspection conditions if they have any communication issues too. I don't see why it should matter but technology is advancing fast. Even in a 2009 model.
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Tuesday, January 3rd, 2023 AT 3:05 PM

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