Using an OBDII Code Reader with an Aston Martin DB9

Using an OBDII Code Reader with an Aston Martin DB9If you are brave (or dumb) enough to do some of your own maintenance on your Aston Martin DB9 one great tool to have in your repertoire is an OBDII code reader.  OBDII stands for On Board Diagnostics version II – an industry standard communication method that modern cars with computers use.   By linking up your OBDII reader to the car, you can ‘talk’ to it, learning some real-time information from the cars Powertrain Control Modules (PCMs).

Aston Martin Check Engine Light
Dreaded Check Engine Light (CEL)

Of particular use is to understand what’s going on if the dreaded Check Engine Light (CEL) comes on.  This is also sometimes known as the Malfunction Indicator Light (MIL) or Idiot light.  Without a code reader you are completely in the dark as what might have tripped the CEL, and at the mercy of a Dealer to find out what’s going on.  With a code reader, you can link up to the car and it will tell you a much more specific error code (a P code in Aston Martin speak).   This will narrow down your troubleshooting greatly, and often it can be a simpler DIY issue to address and then clear the error code and reset the CEL.

Aston Martin’s Official System

Aston Martin AMDS Linked to my DB9
My DB9 linked up to the AMDS computer at the dealer.

When you go to an official Aston Martin dealership, they don’t use some generic OBDII tool, they have a very fancy (and expensive) Aston Martin Dealer System (AMDS) computer that links up to both the powertrain and body system networks in the car.   The AMDS is much more than a simple code reader, it can talk to all aspects of the cars electronic systems, update/flash the software in the computers, reset settings, all sorts of great stuff.   I thought ‘Cool’ – I will just get one of those.   I searched eBay and the Internet, and was able to find one for $14,000 USD.  Sorry, too pricey for me.

Manufacturers and OBDII Standards

OBDII LogoMost any modern car now has computers that run all aspects of it.  The network of sensors and computers in the car is loosely call the Car Area Network (CAN). Manufacturers generally conform to the universal OBDII standards, but most also have a set of ‘custom’ codes that are unique to their brands (proprietary).  This is reasonable, car design is often very custom.   So VW may have custom codes for its Airbag system, and Bugatti might have custom codes for its engine system.   Most manufacturers openly publish these custom codes, and fancier aftermarket OBDII readers do more than just the OBDII standard language, they will also know the custom codes for Ford, VW, and even Bugatti.   The problem here is that Aston Martin has NOT published their custom codes, so aftermarket readers can only speak basic OBDII to our cars, and a LOT of the information is unavailable to us, and only the dealers using AMDS can access it.  Deliberate by Aston Martin I think to force us back to the dealership – bummer.

Aftermarket OBDII Code Readers

Autel MaxiDiag Elite MD802
Autel MaxiDiag Elite MD802

I then started to research aftermarket units.  There are literally hundreds of OBDII code readers on the market starting at less than $100 for a cheapy unit from the local parts store.   I was looking for more than a basic unit, I wanted one that had a bright, large color screen (my eyes are getting older), and that knew as many manufacturers custom codes as possible.   Even though this wouldn’t matter much for my Aston Martin, I wanted to use the reader on my other family members cars as well (BMW Mini, Acura, VW).   My search lead me to the Autel MaxiDiag Elite MD802.   Autel makes many different models.  This is a fairly full featured unit, well reviewed, and even can be ‘software updated’ to learn new codes as each new model year comes along.   Comes in a nice case, very professional unit.   I found it for about $220 on Amazon.

[Updated Dec 17, 2017]

The Autel MaxiDiag Elite MD802 is being replaced with the Autel MaxiDiag MD808 Pro.   Available for about $279 USD on Amazon.com, the MD808 is the newer/better model.  A significant upgrade is that it now includes a lifetime of free updates so it will always have the latest codes for the newest models.  Its still DOES NOT support Aston Martin models directly.   But we have a better option to choose from now.

Foxwell NT510 OBDII Reader

The Foxwell NT510 is a new OBDII reader that is very similar to the Autel, but INCLUDES Aston Martin specific codes and can even reset the Service Required light.   It also includes lifetime free updates and is available for just $149!  This is now my recommendation for an OBDII reader for your Aston Martin and you can read my full review of the Foxwell NT510 here.

Where to Hookup Your Code Reader

Aston Martin DB9 OBDII Connectors
OBDII Connectors

Once you have your OBDII reader, you need to know how to hook it up to the car.  This is very simple.  In the drivers side footwell if you crawl down and look under the dash near the center tunnel you will find TWO (2) ODBII style connectors.  You should see a label on the lower trim piece as well.

  • The connector labelled OBD is for the OBDII code reader.  This is the one we want to use.
  • The connector labelled BODY is for talking to the body system network, things like the Seat Modules, Window Modules, Stereo system, etc. and is NOT to be used with an OBDII Code reader.  If you link up in error to this connector, your reader will likely not be able to establish communication.

There is a difference between Left Hand Drive (LHD) and Right Hand Drive (RDH) cars.  The OBD connector is always the one towards the drivers door, the Body connector is always closest to the center tunnel.

BODY OBDII socket protective cover in place on Aston Martin DB9
BODY OBDII socket cover

The fact that there are two connectors obviously was causing some confusion.   Aston Martin issued Field Service Action 144 (FSA-144) in June 2006 instructing the North American market dealers to install a protective cover/boot overtop the BODY OBDII connector to minimize the chance of an incorrect connection.  You can read the entire FSA-144 here.  My car was built before this FSA was released, and my Damn Previous Owner (DPO) or his dealer didn’t get this done while under warranty, so my car hasn’t had this modification performed.

Using Your Code Reader

Establishing OBDII Communications to an Aston Martin DB9
Establishing Communication
OBDII Code Reader Information connected to Aston Martin DB9
Current ODBII Data

So, now crawl into the footwell, find the OBDII socket, and connect your code reader.   My code reader gets its power directly from the car, so it powers up immediately.   Even with the car off, the unit will power up.  But, I have learned for communications to work, the ignition key will need to be in Position 2.   The car doesn’t need to be running (it can be though).   I then need to tell my reader to ‘connect’ to the car and establish communications to the CAN network.  This just takes a few seconds and then Ta-Da!   You’re talking to the car and now can view P codes, live engine data and more.

Check out this short video of me showing where the connector is and linking up.

Here is a post on the 45 live data parameters available when you connect using generic OBDII codes.

I also have a post about how to get many more (200+) live powertrain parameters by asking your OBDII reader to talk to the PCM using Ford factory proprietary codes.

Also this post that lists the 200+ engine parameters.

6 thoughts on “Using an OBDII Code Reader with an Aston Martin DB9

    1. P Codes article is coming along, but the next one soon to be released (insider preview) is actually a trick I just learned. Rather than using OBDII on the Scanner, use Scan, Select Ford of Europe, Manually select the engine, and select a 3.0l V6 from the MY2005. You’ll get a ton of usable information. The Tire Pressure Monitoring system isn’t part of it, I believe the TPMS has its own reader, and even separate connection in the trunk. Stay tuned for the full article on the Ford method.

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      1. Joel

        Hi Steve,

        Let me start off by thanking you for your efforts in advancing knowledge for us DIY-ers. It must take a great deal of time to shoot, edit and write these posts, and I thank you for it.

        I recently purchased a DB9 (2009MY) with about 50,000 mi (81,000 km) on her from a local AM dealer. The vehicle had two previous owners. At the time of my test drive mid-August everything seemed generally fine with the vehicle. Or at least I thought so. Most importantly, there was no MIL/Check Engine light on. I purchased the vehicle about a week later, and because I was about to take an extended vacation, did not take delivery until last week (Sep. 22).

        When I picked up the car, I noticed the MIL was on and displaying the ’emissions service’ message. I asked the salesperson about this and he said not to worry about it and that it will disappear, claiming gas cap issues. Subsequently I did some reading, learning about gas cap issues, etc. I checked the cap and it is white, and fully closed. I also discovered your blog, read all your posts, and last night purchased the same OBD-II reader you have (Autel MaxiDiag MD802). While I haven’t had a lot of time to review data, I did learn that there are significant misfires on cylinders 5, 6, 10, 11 & 12. I also have some PATS codes, but not sure about them. A snippet of my data is below. I have the following questions:

        1. The data I have shows DTC’s were cleared just prior to my test drive. How could the test drive not have the MIL showing given the extent of misfires being generated?

        2. My understanding of cylinder numbering is that left bank is numbered 1 to 6 (front to back) and right bank is 7 to 12 (front to back). Is this correct? If so, my cylinder misfires are at rear of engine on both left and right sides. My understanding is that this does not seem likely point to a vacuum issue as these are usually isolated to left or right banks, but I’m not sure about that. Any comments?

        3. I understand that when things get really bad, cylinders get shut down, but not sure if damage to catalytic converters can still occur given the extent of my misfires. How risky do you think driving the car is in this condition?

        4. Do you know what the $80 to $84 Mis-fire Monitor Tests are? (See Mis-Fire Monitor Data below).

        5. The quantity of mis-fires on my cylinders seems high to me, but not sure if that’s true (having no prior experience with these matters). How severe is this?

        Thanks for your time Steve.

        Joel

        —————————————————————-

        Trouble Codes
        P0300 $07EE
        Random/Multiple Cylinder Misfire Detected
        P0311 $07EE
        Cylinder 11 Misfire Detected
        P0316 $07EE
        Engine Misfire Detected on Startup (First 1000 Revolutions)

        —————————————————————-

        Mis-Fire Monitor Data
        $80 Test Status: OK
        $81 Test Status: Fail
        $82 Test Status: Fail
        $83 Test Status: Fail
        $84 Test Status: Fail

        Mis-Fire Cylinder 5 Data
        EWMA Misfire Count 44
        Misfire counts Last 262

        Mis-Fire Cylinder 6 Data
        EWMA Misfire Count 10
        Misfire counts Last 100

        Mis-Fire Cylinder 10 Data
        EWMA Misfire Count 66
        Misfire counts Last 114

        Mis-Fire Cylinder 11 Data
        EWMA Misfire Count 487
        Misfire counts Last 994

        Mis-Fire Cylinder 12 Data
        EWMA Misfire Count 100
        Misfire counts Last 198

        —————————————————————-

        Fault Codes(3)
        B1600-FF CMDTCs
        PATS Ignition Key Transponder Signal is not received.
        B1601-FF CMDTCs
        PATS(Passive Anti Theft System) received incorrect key-code from ignition transponder.
        P2800-FF CMDTCs
        Transmission Range Sensor B Circuit (PRNDL(Selector lever position (PRND321)) Input)

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      2. Hi Joel. Thanks for taking the time to write, and I appreciate the Kudos. Sound to me like they might have reset the MIL just before your drive as you suspect.

        I am no AM mechanic, but I’d say you have a couple of separate issues going on. The Misfire issue seems to be the biggest at the moment. Member the misfire count resets each time you drive it, so those are significant numbers. I think the shutdown percentage is at 1.5% or so. P311 and P316 are those cylinders having serious issues.

        The PATS issues might be separate.

        THis is going to sound stupid, but I’ve never been sure on the cylinder numbering schema. Something I need to nail down, but I can’t even find it in the manual. If you find a solid online reference, please let me know.

        The S tests its referring to I don’t know what those are either (yet).

        I guess if you have any leverage with the dealer, take it back with this data and tell them you want a refund unless they address coil pack issue by replacing all 12 packs, plugs and bits. No selective replacements. Ditto for the other P Codes. If you are stuck and they won’t do the work, I think I’d start with doing all the coils and plugs and PCV stuff first, then clear all the codes entirely using your reader, then see how it settles out afterwards.

        Would I drive it in this state? Not really. Moving around in the driveway, or maybe back to the dealer, but I wouldn’t do any regular driving.

        Let me know how it turns out.

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