Not all systems are diagnosed through the OBD2 port.

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Apr 27, 2010
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This many not be news to some, but I just figured it out now. I started up my 1999 Altima with the airbag out of the steering wheel, so of course the light was on. So I figured no big deal, I’ll just erase the code after reinstalling it. When I connect the scanner through the OBD2 connector and go to the AIRBAG section, it says no communication with the module. I try rebooting, jiggling the connector, charging the battery, etc. and nothing. Waste an hour doing that. Go to the generic OBD2 screen and no problem there, connects and reads the emissions related systems just fine. Turns out there is another connector by the fuse box as well. Check the box my scan tool came in and it has a dozen adapters including one for Nissan. Plug into that and now I can scan everything. I was under the assumption that all cars since 1996 when OBD2 became universal, would be able to have all the systems read from there, and only the 1995 and older models would need one of those adapters. Just a PSA if your tool isn't connecting. I assume this applies most for the first few years of OBD2 until the car makers enabled ALL systems to be scanned through the OBD2 connector.
 
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Apr 25, 2017
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Is it possible that ABS, SRS, etc systems aren't required, or weren't at that time, to be accessible through the standard OBD2 port ? Many consumer-level scanners still can't access this data either so maybe it's related. Over time, automakers seemingly have tried to integrate things (??).
 
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Apr 9, 2008
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Fun fact, not all cars were fully OBD2 compliant in the late 90s. Also larger trucks use a completely different connector, we can't work on or diagnose any issues with a F-650 or F-750 with a Caterpillar or Cummins engine.

I was surprised to learn that my 2001 Grand Marquis is just EEC-IV with some OBDII functionality slapped on top.
 
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Oct 3, 2008
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I was surprised to learn that my 2001 Grand Marquis is just EEC-IV with some OBDII functionality slapped on top.
EEC-V with a 104 pin harness connector. Easiest way to tell; EEC-IV has the diagnostic connector under the hood and EEC-V has it under the dash.
 
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My pickup threw a code when the batteries died. Glad I could clear it with my inexpensive reader. Money well spent.
 
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Also larger trucks use a completely different connector, we can't work on or diagnose any issues with a F-650 or F-750 with a Caterpillar or Cummins engine.
I don't know who required the switch to OBD2 (NHTSA ?), but maybe it only applies to non-commercial vehicles. Automakers are free to implement it elsewhere if they want though.
 
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Different modules on my 2016 are accessed by HS or MS Canbus. I need a switched adapter to access all of them so even now, there is no universality.
Aren't the ECM, TCM, etc all on the standard bus though ? Our '14 Fusion needs a switching adapter as well in order to access ALL of the modules. I'd think that the OBD2 requirement might not apply to the radio module, climate control module, etc.
 
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Jun 3, 2005
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Aren't the ECM, TCM, etc all on the standard bus though ? Our '14 Fusion needs a switching adapter as well in order to access ALL of the modules. I'd think that the OBD2 requirement might not apply to the radio module, climate control module, etc.
On the Ford side we just use the IDS with a VCM 2 or 3. Well new stuff uses FDRS instead of IDS.
 
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Oct 5, 2005
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And a few were before '96, some Ford and Mercedes.

The 1995 Mustang with the 3.8 V6 and 1994 (or perhaps 1994 1/2) Mustang with the 3.8 V6 had an OBDII system or at least an OBDII beta system that uses the OBDII plug to attach your code reader. The 1995 Mustang 5.0 V8 and the 1994 Mustang 5.0 V8 still used the pre-OBDII system.
 
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Jun 15, 2003
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Of the 16 pins, you get emissions data on "a few" depending on the protocol (though CANBUS has been required for a while now.) My Prius puts the TPMS on a different pin (within the same connector) and different protocol. It's the first thing to fail to work if I use a cheapie dongle from the dark depths of "Receive and Duplicate."
 
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Don't forget, some vehicles have TWO OBDII ports, a la my Volt. One on the driver's side, one on the passenger side.

Or, the infamous OBD 1.5 cars from GM in '94-'95. OBDII port with OBDI protocols.
 
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Dec 19, 2013
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Nissan did that well into the 2000's, Only the bare minimum of systems & data was assessable through the OBD2 port. Toyota's had their proprietary Diag Port under the hood of many early OBD2 vehicles though I can't recall using it very often......Flash out ABS codes IIRC.
 
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Oct 10, 2021
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I have a bludriver. But am still pretty new to using scan tools. Fixed my abs wheel sensor with my bluedriver and it paid for itself first use.
Borrowed a super basic tool for my 02 grand marquis and found a bad coil pack and cleaned the mass air flow sensor to make that car happy a few years ago.
Dont think i am smart enough for a expensive scan tool yet.. maybe some day
 
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