Could be. Feel free to share the report if you want. I'll message an email address if your'd rather

C

 

p192300 check dtc memory of Engine control module

p068a00 ecm/pcm power module performance

p304500 fuel pump electronic faulty

p0546ccexhaust gas temperature circuit bank 1 high

 

Was this from VCDS?

C

 

Independent service guy's scanner. I will ask what equipment they've used.

Excuse my ignorance but would the codes be the same across the different manufacturers?

e.g. p0546cc...the same nomenclature from Ross to the others?

 

P-codes are defined by OBD/EOBD. Scanners across the board will read a P0546 defined the same way.

P0xxx codes are universal across all manufacturers, so a P0301 is a misfire cylinder one in any car.
P1xxx, P2xxx. P3xxx, codes are manufacturer defined, and don't often cross over one mfg to another (but sometimes will) but will within the mfgr.

For example, the P1923 which comes up a lot in Bentley is a "check code" to reference the second ECU and used in this instance with a two ECU EMS. It's not seen in other manufacturers.

The second digit in a P-code (e.g., the 3 in P-0301) defines the emissions category
P01xx= fuel and air
P02xx= F/A Injector
P03xx= Ignition
P04xx= Aux Emission
P05xx= idle and speed control
7,8,9= Transmission
A,B,C= Hybrid

These code categories are OBD, EOBD defined
P-Codes = Powertrain
C-Codes = Chassis
B-Codes = Body
U-Codes = Network
You can find explanations all over the internet. Quick Google brought this one up which is pretty good:
https://obd2pros.com/dtc-codes/

 

The link was very informative.

My understanding of the codes is that they seem to be (what we would say in medicine) "non specific."
So, they don't tell me to just replace the sensor per se, as the problem may be something before or
after the sensor, that trips the error code.

I'm assuming the dealer bandits would simply suggest replacing the temperature sensor(s) which may or may not
eliminate the error code.

Finally, would all or some of the detected error codes trigger the dash ECU light to go on, or just the exhaust gas temperature fault P0546cc?

 

You're pretty intuitive - codes seldom point directly to the issue, but more in the general direction

Example - a P0301, misfire cylinder one:

The first thought is a misfire means something to do with spark/ignition - spark plug, ignition coil, related wiring

If nothing there solves it, then a little more thought needs to go into what causes the cylinder to fire in the first place? It needs Air, Fuel, Ignition.

So, even if the title of the code suggests ignition, could be myriad other things starting with
Bad fuel injector
Compression in that cylinder
valve issues
etc.

Often a single failure can generate a number of codes.
Don't focus on P1923. It just tells you to check for codes in ECU #2 and is not a fault itself.

With the other 3 codes you're seeing, any one of the 3 could be the source and as a result of its failure, triggered the other two. I'm new to this thread, so haven't had time to absorb what you're dealing with.

Funny how engine management systems perform. They often use logic and algorithms to process data from tables. Where the ECU was at any moment when a parameter was exceeded can cause quite a variance in the path it follows of the same problem, often then reporting other exceptions as it sees them. All happening pretty instantly.

EDIT - Didn't see the part in your reply about dealers - YESYESYES - Dealers are trained to replace parts first, then diagnosis (because it gets expensive) comes when the parts replacement fails to solve the problem. Dealers' techs, typically, are not good at diagnosis.

 

I'm just a weekend driver, but I suspect one fault triggered other faults. I have a feeling the dash light will simply
come back if the underlying fault is not identified. Seems like it will be very difficult to trouble shoot given that
the car drives magnificently. Very discouraging to be honest as I can't see how a technician can diagnose these
things in the absence of obvious defects.

I will get the car back on Monday, after the routine annual service is competed, and report back.

I appreciate the comments.

 

Muddling through the dash light warning which shows an engine graphic, and the manual calls ECU. Is that Emissions Control Unit or Engine Control Unit?

 

ECU (or sometimes called ECM) is Engine Control Unit (engine control module).

All Powertrain related faults (P-codes) generate the check engine light only.

B,C,U-codes do not generate the check engine light. Instead, they're conveyed through some other, usually written out fault messages in the dash unit, or with fault icons.

Another bit of information - most scan tools, the simplest of which can cost only a few dollars are only capable of reading simple P-codes, nothing else. Much more expensive universal tools can sometimes read all fault codes in all categories, sometimes with mfgrs' special software; then dedicated tools are very manufacturer specific only. VCDS is one of those manufacturer specific tools for VAG cars and can read all faults in all VAG cars. If you have a VAG car it's a goto tool.

Same with all the manufacturers. They've all developed their own proprietary engine management systems. For my AMG GTS the goto tool is Xentry, for example. With GM it's Tech II (used to be but was just upgraded with GMs new B Architecture)

 

Am I correct then, that the P codes can be very specific in some cases, and very NON specific for other faults?

 

Well to @BWings example of P0301 is very specifically a misfire on cylinder 3. But non-specific as to *why* it's misfiring.

VCDS tends (IME) to be rather better in this regard, but by no means perfect.

C

 

Yes, sometimes the P-code can be very specific.

Whenever I am able to demonstrate how faults come to play and are recorded to a newcomer, we start with a good example, no codes, no check engine light. I unplug the cable to the MAF w/o them seeing it. I have them start the engine. The check engine light comes on almost immediately. I have them shut the engine down, plug the scan tool in and read the code. P-0101 comes up. They look up the code - Mass air flow (MAF) sensor/volume air flow (VAF) sensor range/performance problem. They check the MAF and find the cable unplugged. They fix that, then use the scan tool to delete the code. Then restart the engine to find the check engine light extinguished. It's one of the simplest diagnostic examples.

After that simplest of examples it gets more complex from there.

 

My manual is in the car at the shop. My recollection is that the manual called the dash light icon which looks like an engine, Emission Control Unit,
but I'm thinking it is Engine Control Unit. My point is I think I've been mistaken to say I've got an emission fault. I will know next week when I pick up
the car, but I'm thinking clearing the codes I noted will simply recur after driving a bit.

"Intermittent" faults may go away with clearing in terms of the "check engine" icon coming back?

 

You're not mistaken. Technically, power train codes are all emissions related either directly or indirectly. The orange check engine icon represents an engine fault that impacts emissions. The acronym ECU is engine control unit.

SOME faults can clear themselves (w/o using a scan tool) when certain drive cycles are completed. The gas cap is the most popular one. Most however, do not.