The anatomy of the fault code

   #1  

DrPeter

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Fault codes can be a wealth of information!
.. and we sometimes overlooked this. Here is a basic guide to understand some of the components of the fault code.





We can break down the fault code into the following parts:

- The fault code numbers
- The fault code description
- The freeze frame data






Fault code number-

When using the Ross-Tech tool, the fault code number displayed will have a unique Manufacturer (VAG) number and sometimes a SAE-(Society of Automotive Engineers) number. SAE numbers are standardized , they are not unique to the manufacturer and will share the same ‘standardized’ meaning whether it is read from a controller on a domestic or an import vehicle.

The manufacturer specific fault code will not have an SAE number equivalent and are found mostly in controllers other than the Engine or Transmission, such as HVAC or VAG specific controllers.


Fault code description-

One of the most overlooked part of the fault code is the description. We, at Ross-Tech Technical support receive a lot of questions about fault codes, from 'what does the fault mean?' to 'I can not find it the Ross-Tech wiki page', note: Not ALL fault codes are listed on the wiki pages, we are working on it, ;)

The code below is an example and I explain the definition in some detail.

P1527 - Bank1; camshaft adjustment -N205: Short circuit to ground

The fault above tells us the ECM has detected the N205 'circuit' (on bank 1) has been or is shorted to 'ground'.

- Okay some folks are saying this is obvious, how do I fix this? This is the part where most people get a bit confused and need help.
Diagnoses will require an understanding of the N205 function and circuit and the way it is connected to the ECM. We will not get into too much detail here, this is not a repair manual.
- You will want to take a look at a wiring diagram, there you will see the N205 has battery voltage to it on one side with the key on(15-power) and the ECM is the source of the ground when the N205 is activated.

- The ECM is actually monitoring this circuit(when the N205 is not active) for the battery voltage that will travel through the N205 and if there is no detected voltage, rather a grounded circuit, this fault code will set.
- So you will need to check for the following:
1) Fuse/power
2) wiring/connections
3) failed N205
4) failed ECM


Freeze frame data-

- Fault Status = The binary value indicating the state at the time the fault was recorded
- Fault Priority = A numerical classification of the importance of a fault code
- Mileage/time/date = Some controllers have no idea what the true date/time is, this data maybe wrong.
- Fault frequency = How many times the fault occurred.
- RPM, Load, Temp, Absolute Press, Voltage = Misc info



- - - Final notes - - -
- Freeze frame data is very useful when attempting to isolate the particulars of a fault code that may only happen in a small window of conditions.

- Reading fault codes, understanding them and knowing how the systems function is crucial if you are to successfully diagnoses and repair Volkswagen, Audi, Seat, Skoda and Bentley vehicles.

- Repair information can be found here:
Official Factory Repair Information
 
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Moxnix

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Hey thanks for this Doc, very clear and helpful.
G
 
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Jef

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I'll add to this a bit more info on fault codes....

Some fault codes can have more than one DTC code, in some cases 3 variants of the code for the same thing. Sticking with the misfire DTC example from above:

16684/P0300/000768 - Random/Multiple Cylinder Misfire Detected

We have 3 DTC numbers here, 16684, P0300 and 000768.... all of those DTC codes are for the "Random/Multiple Cylinder Misfire Detected". Maybe Seb will chime in and explain why this came to be.

When talking about fault codes, it is VERY important you give a complete number. For example, people will say they are dealing with a "OH-300" code. :confused: Miss Manners says you should instead state you have a P0300 fault code.

Also note that any time there are a bunch of zeros in front of a fault code, they are part of the fault code. 000768 is a misfire. 00768 is not a misfire, but a problem with a G154 sensor for a rear heater core. If you were to even say a 0768, one might think you mean P0768 which is a code for a Shift Soleniod #4 (N91). So 000768 is always stated as 000768, never shorten a code.

Last, some codes that are specific to VW/Audi can be broken down into 2 parts... [this part] has [that problem]. For example:

00778 - Steering Angle Sensor (G85)

The Steering Angle Sensor (G85) can have different types of issues:

  • Faulty
  • Implausible Signal
  • No or Incorrect Basic Setting / Adaptation
  • Not Matched
  • Mechanical Failure

So if you tell some one you have a DTC of 00778, you are saying [this part], the Steering Angle Sensor, but not stating what the problem is... [that problem] of Mechanical Failure is a different problem than Not Matched.

Kudos for Peter for the chart above.
 
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aTOMic

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Wow, DrPeter, I cannot TELL you how helpful that first post is!

Is there any way you could post the text so I could copy/print it? I know I could print the image but the highlighting, while useful, could obscure the text.

Regards,
Tom
 
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Dana

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Hmm, the guys watermarked that so it couldn't be stolen easily (that happens often) but the Fault Priority text is available on this page of our Interactive manual:

http://www.ross-tech.com/vcds/tour/dtc_screen.html

I'll point this inquiry out to Peter and see what we can do for a printable version.

-Dana
 
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aTOMic

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Thanks for the reply, Dana. I printed it just as-is today; chose grayscale, and it's hardly noticeable that the original is highlighted.
I was worried about the highlighted/colored background, the watermark isn't a problem.

Regards,
Tom
 
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