In a previous post I explained how you can hook up an aftermarket OBDII Code Reader to your DB9 to retrieve Diagnostic information from the Power Train Control Modules (PCMs). What’s disappointing is that Aston Martin has kept much of their code system proprietary (accessible only via the Dealers more advanced AMDS system) and thus we can only get rudimentary information using the generic industry standard OBDII codes (check out my post on the 45 pieces of data available using this method) .
On a lark I thought “Since Aston Martin was owned by Ford when the DB9 was initially designed and built, maybe the PCM’s are really programmed with Ford codes”. There was some clue to this as well on the Aston Martin Technical Information website – in the early years of the DB9 the Dealers used the WDS system to access the PCMs (the predecessor to the current AMDS), which I discovered is Fords Worldwide Dealer System. If the WDS is designed to talk to all the Ford models of the world would work for it, maybe this would work for me too.
I connected my Autel MaxiDiag Elite MD802 Code Reader to my DB9, and rather than telling it to communicate using the Generic OBDII standards, my code reader has an option to specify the Manufacturer. I selected Ford of Europe. It then had options to ‘Start New Session’ where it would automatically detect’ the PCM, and this didn’t work well, returning a ‘The unique PCM identifier is unrecognized’ error. OK, so it doesn’t know what an Aston Martin is, but this doesn’t mean it isn’t a Ford part that been told to identify itself as an Aston.
I pushed on, and my Code Reader has an option to manually tell it what type of Ford PCM I was connecting to. I selected:
- All MY05 Escape/Tribute/Maverick/Mariner
- 3.0L V6 (the only other option was a 2.4L 4 cyl, so I thought since the DB9 has two PCMs, each one controlling 6 cylinders, and our cars have 6.0L V12s, maybe the 3.0L V6 would talk to one of the controllers properly)
- 4V (presuming this means 4 Valve, but it was the only option anyways)
- 2005 MY (this choice was the only one available and was correct, so I suspect it was able to query the car some to get this right)
Next it asked me if I wanted to Auto Scan the entire vehicle for all possible modules, or I could specify just a particular scan to perform. I selected Control Unit and then the Powertrain Control Module.
After these selections, my Code Reader starting to talk to the PCM, and in about 30 seconds I could Read Stored Codes, Erase Codes, and I was able to see close to 200+ real time pieces of Live Data that included potentially useful service and troubleshooting information like:
- Is the brake pedal depressed
- Is the A/C clutch engaged
- Idle speed
- Ignition advance
- Transmission gear
- Air Intake Temperatures
- Mass Air Flow sensor flow rates
- Fuel System Pressure
- Cylinder Misfire Count
- Misfire Correction Factors Learned
- … and many, many more items that you can read in this separate blog post.
The Misfire Correction Factors Learned is a great one to know about as I discussed in my other post, and is a piece of data I thought I would only be able to get with a visit to the Dealer using a AMDS.
Only Half the Story
Does this give us DIY guys as much information as the Dealers AMDS? I don’t think so. One certain limitation was that I was only seeing six (6) cylinders of information, not twelve (12). As I mentioned there are two (2) PCMs running our DB9s engines (like two separate six (6) cylinder engines that are interwoven). I suspect my approach here is just talking to the primary PCM, and there is no way to switch over to the secondary PCM to learn the specific information only it might know. And of course, who knows if there are even more Aston Martin proprietary codes beyond the standard Ford codes that might hold even more information.
Anyways, this technique expands our arsenal of information and is better than what we can just get with an OBDII standard common codes.
Here is a short video just showing setting up the communication as a Ford 3.0l V6, and then a look at all the information available to you.