Help with these codes?
 

The "ECU" code and Exhaust Temp Bank codes have been persistent after I cleared them 100 miles ago. But the Performance Malfunction is new and put on the Check Engine Light.

Any thoughts? Connector? Bad probe?


3 Faults Found:

18331 - Please Check DTC Memory of ECU Number 2

P1923 - 008 -

16929 - Sensor 1 for Exhaust Temp Bank 1 (G235)

P0545 - 002 - Short to Ground

18613 - Performance Malfunction in Cooling System

P2181 - 008 - - MIL ON

P1923, suggest making sure that the ECU connections are not corroded. They are under the plastic windshield wiper shroud. There are two units. They are on the passenger side tucked way in back of that space. Commonly the space below the windshield wipers tends to fill up with debris and then there is possible water Ingress. There are old posts regarding cleaning out this area.

P0545 common problem exhaust temperature sensors go bad. This one refers to bank one which is the driver side. I do not know of any test for this sensor other than buying a new one. The main function of this sensor is to protect the catalytic converter. This could result in a bigger problem if neglected.

P2181, this might be a bad coolant thermostat. The computer picks up if the warm up cycle is taking too long or is too short depending on what the malfunction is. Replacement of the thermostat isn't difficult but the part is a pricey.

Unfortunately sometimes replacing components doesn't result in fixing the problem. I would start with the ECU and making sure it is not the culprit. Check the ECU terminals for corrosion : First.

I agree with Eric about throwing parts at P-codes. They almost always create a pathway for diagnosis and seldom give you a direct parts replacement. I take a slightly different view of these codes.

On 18331 - just ignore this code. The two ECUs are constantly shaking hands. When ECU2 (address 11 secondary ECU or slave) reports errors, 18331 is set in ECU1 (Address 01 primary or master ECU). Once the errors reported in ECU2 are fixed, 18331 will extinguish. Simply delete it AFTER 16929 and 18613 are fixed. It won't come back and nothing to fix.

Your focus should be on 16929 and 18613.

16929 or P0545 is a bank one EGT sensor. A short to ground here is probably the sensor, but I agree with Eric to check as much wiring as you can for a shorted +5v feeding the sensor. The sensor is nothing more than a variable resistor (thermo couple) operating in the range of 1v to 5v in front of the CAT(s) it's main lot in life is protecting the CAT from overheat. This is probably what is causing the performance malfunction as the ECU cannot get any v range reading with a short to ground. So, bottom line - look for a wiring short or bad EGT.

Look for the EGT on the right side bank (as you are sitting in the car looking out the windshield). Bentley W12 bank and cylinder ID are:

https://cimg7.ibsrv.net/gimg/www.6sp...7506b80b64.jpg

On the 18613 - Here too, as Eric has explained, the ECU is reporting an out of range coolant temp based on a check MAP it uses. This is a good example where a number of different components can cause a P2181, which usually does NOT lead to a performance malfunction. In other words, other than the CEL illuminated, you should be able to drive normally. One way to get closer to the problem component is to datalog. Doing a DL of coolant temps, done from cold, can sometimes help identify a stuck/bad/open thermostat vs a bad coolant temp sensor based on the ramp to operating temp, then examining the temp line and how it holds during operating temps. A stuck open tstat, for example, might not ever reach the op temp range the ECU is expecting to see; stuck closed the opposite, but a stuck closed Tstat would cause a lot more visible issues than just an improper feed to the ECUs. A bad coolant temp sensor can produce an erratic coolant line in a DL, or dropouts where the actual coolant temp couldn't change that way, that quickly.

If this were mine, I'd be putting all my focus on the P0545.

Indeed the exhaust temperature sensor is suspect. My understanding is it comes into play under heavy load when the turbos are at play. Without this intervention the exhaust temperatures can spiral out of range and be damaging to the catalytic converter.

Experience has shown that sometimes the sensors fail internally resulting in a short to ground. The use of non lead-based solder on the PCB boards leads to micro-cracks. Follow the suggestion of Mr. BWings can avoid replacing the exhaust sensor unnecessarily.

Seeing that the car lives in Chicago I still would check the ECU. Furthermore cleaning out the plenum below the wipers will avoid expensive issues later on. My memory of Chicago is dirty. Who knows what might be lurking in that Abyss.

Yes I agree bank 1 is on the passenger side right side. I think that exhaust temperature sensor is easier to change than the opposite one on the driver side.

Please keep us posted when you have results.

Yes, I agree, preventive maintenance is always a good thing. I've had my cowl off twice now in a year, just to keep things spotless. I also run water directly into the well at the driver's side (left side by the brake booster) to ensure water is draining (you can see it run underneath when the drains are very clear) and not filling up to pan.

These won't fix the two faults though. Mr. British must focus on the RS EGT especially, and probably the coolant sensor too.

If it were me, I'd first do the EGT, then clear all the codes and run it; see if P2181 returns on its own. If so, only then would I work through it. I've seen this code too many times on Euro EMS designs. The map the ECU uses to compare, especially on the coolant warmup ramp is too sensitive. When the sensor gets old (and a little lazy), and with certain air temps at some times of the year, the coolant algorithm momentarily "leaves the reservation" setting the CEL. Clear it and it doesn't come back for another year.

Thanks for taking the time to help, guys. I'll keep you updated.

I suspect mine has a very similar fault .Its intermittent ,only occurs in very cold temps ( winter starts from a cold garage in the Alps )
it throws a CEL and the DTC code I get P1924 .I only have a basic reader .How ever Audi forums say it’s a coolant temp senor gnd .
My tech in the U.K. had the full diagnostic kit and due to the intermittency it’s difficult to replicate when I return to the U.K. ( usually after the winter )
In Switzerland if I don’t clear it and take the car to the valley and say shop ( lots of restarts when it’s warm and the outside air temp is warmer ) the CEL spontaneously can go off .

So this “warm up ramp “ thingy makes sense to me .

Back in the U.K. my tech did say from his end it was something to do with the way the two ECUs talk to each other , he thinks one or both have been updated by way of emptied first then new software uploaded and in his experience you can get odd software errors .
As said early on in this thread he did not suggest throwing new parts at it and advised me to just keep an eye on it .

car runs faultlessly the P1294 CEL only comes on with a very cold start .Perhaps 2 mins into manoeuvres out of the drive .

I did ask a couple of years ago what this code was but the forum seemed silent then .

Does what I say make sense ?

Perhaps related they found a Lamba sensor in May last year was faulty and replaced that .My simple code reader did not pick up on that .

Has anyone got more info on P1294 .Is it related to cold start ramps ?
i,am talking sub zero ambient temperature here btw

Regrettably sometimes these digital trouble codes result in a lot of time spent only to discover that ignoring them would have been a better solution. However ignoring them can result in problems, so here we are.

Back to the exhaust temperature sensor. One way to confirm age of the sensor is if it's a brown housing, that's an old "slowpoke". The new upgraded ones are black. In my humble opinion if it's brown might as well change it. That could fix the problem and definitely avoid the problem in the future. The overwhelming majority of brown exhaust temperature sensors are in the junk pile.

Makes sense to me. A short primer on P-codes: P-0xxx codes are generic, so a P-0300 is a "multiple misfire" code whether it comes from a Bentley or a Kia or a Ford. P-1xxx; P-2xxx; P3xxx; etc., are manufacturer specific codes. Manufacturers can define these as they wish, although they try to stay within general definitions.

A P1294 is a cold startup fault code and, generally, is defined the same across most manufacturers. However, because of powertrain design idiosyncrasies, a cold startup fault could have different sources of failures across different manufacturers. For VAG EMS designs, it almost always is caused by a faulty ECT sensor. Here is one example on an Audi:
https://cimg3.ibsrv.net/gimg/www.6sp...5b5cc37dc7.png

Engine management systems are all similar in that the ECU is constantly using fixed tables that often have a time element to compare/confirm where certain run parameters should be. If they fall outside thresholds, the ECU cannot proceed and sets a CEL. Sometimes these are only momentary such as a second in time. The input sensor might be getting slow at certain places in its range, but good in others. So a CEL could be set for that moment yet all the other EMS parameters are being met for all other conditions. The CEL will remain, however, until that code is addressed. And, in my experience, especially with warmup ramps, I've cleared codes and run for months and months without a return.

Startup/warmup ramps are particularly detailed. As I've tuned certain model US cars, idle/startup is one of the most difficult tune parameters to setup. You wouldn't think so, but it's the most complicated part of an electronic tune. In cold startup, the EMS is striving to close loop. The ECU is relying on several sensors, all of which must ramp according to maps the ECU is using to compare actual sensor inputs to design expectations. Some of those sensors are - MAP, MAF, O2s, ECT, TPS, IAT and, the EGT as is the subject of this thread.

I'll show here a typical SIMPLE map, once again, used in an EMS that is not VAG, but VAG will be very similar. This is an actual tune map from an E38 ECU used on many GM LS3 V8 engine applications. In this map, the primary input sensor is the ECT. It is ramping up with a cold start. The ECU is comparing that ramp against the Y axis which is a time element in seconds, against an X-axis coolant temps. The ECU output here is setting the cold engine RPM.

https://cimg6.ibsrv.net/gimg/www.6sp...b4e1249ec9.png

So, lets say we have a lazy ECT at 44*F and the ECU is stuck at 825 RPM and we are now way past 10.6s. Even though the ECT might get past that flat spot and perform normally in the rest of its range, the ECU will set a P1294 (in the case of a VAG EMS) yet the engine is running normally at op temps.

So I'm not stealing British's thread, the EGT is working in a similar way, the ECU is using predetermined maps and expects to see an exhaust temp within a certain range given all other running parameters. if the thermo couple (EGT) fails at a moment in its range, the CEL P0545 will be set. Unfortunately, since exhaust temps are critical with boosted engines, the limp performance mode is also set and will not correct until the problem is fixed and code deleted. Even though the failure might have been momentary. But it also could have failed completely which thermo couples often do. There is a 90% chance Mr. British's issue is a failed EGT bank one. Maybe only a 10% chance he'll find the problem to be a frayed harness or shorted out cable.

Sorry for the length of this post folks......

I believe there's been a bit of a transgression of Mr. British's query. One of the trouble codes was p1923. This is the one that started me on the discussion of cleaning out the plenum below the windshield wipers and checking the ECU connections. Perhaps I'm off on a tangent but I don't think so. Somehow p1924 developed into the discussion which was not part of the original inquiry. Always a good hearty interesting discussion nonetheless.

Eric,

British has 2 fault codes. They are -
16929 (p0545) and
18613 (p2181)

Don't mistake 18331 as a fault. 18331 is a NOTE, not a fault, so there is nothing to diagnose, nothing to solve. I made mention of that in post #3. Here is Ross-Tech's definition and diagnosis of 18331. You'll notice this is nothing more than a note (notice) to check ECU2 for faults. In this case ECU reports two faults - p0545 and p2181

https://cimg8.ibsrv.net/gimg/www.6sp...10dac36c31.png
British has TWO issues to solve, the more serious of which is the P0545, second is the P2181. If he corrects those two issues, then 18331 will extinguish by itself.

To your point, these threads can and do morph sometimes. John brought up a similar issue, but maybe not completely on point. Still British's issues weren't ignored or discarded in favor of a new topic. British responded with an acknowledgement and a thanks. I'm concluding he is now off working on these faults.

I see this as all good. Hopefully both British and John have some good info on which to proceed....two for one......

Thx Mr Bwings for the excellent explanation and oppolgies to Mr 1eapplebaum .
Just highlights the complexity of all modern cars theses days .

Back on Bentley , GT,s my U.K. techs often say they have cleared codes that I knew nothing about but don’t throw a CEL when they service it .

Its asymptomatic btw when they work on it .

I ask and they say “they all do just minor stuff insignificant “
We have learnt some intermittent errors correct after a few start cycles like the P1294 after a very cold subzero start .

We agree chucking new parts on is not necessarily the best first course of action unless you are absolutely sure based on previous experience.

We learnt there are a few poor designed connectors exposed to heat cycles which fail - newer upgrades available.

We have reinforced the need to ensure the middle drains under HVAC unit under the scuttle needs to be regularly cleaned and tested .

We have reinforced possible potential for corrosion with the multi pin ECU plugs on top of the two ECUs under the scuttle.

Well put John and good advice.

So there is no bad blood anywhere, and since this is British's thread, British, if you feel that we've taken over your thread and/or ignored your issues or request for help, I'll gladly take down my posted reply to John's query. Just say the word, no hard feelings about it on my part.

Ah geez no! I am so happy you guys are all willing to take the time to put pen to paper, or keyboard to forum to help everyone else out. I have learned so much from here and everytime I'm stumped, someone steps up to lend a hand.

I'm a big car guy my first car was a Kharman Ghia at 16, second a Triumph GT6, third a Triumph Spitfire, then on later to a Lotus Esprit...I live for this stuff.

I have to admit, I am a neophyte when it comes to these microcontrollers and the fault codes generated and stored. I have the Ross-Tech VCDS and have been sorting through it, with help from you guys. I suspect I have a bad Exhaust probe, or connector, that fault shows up persistently. But until reading this, I had no idea there were "notes".

Lastly, I bought the Bentley service manual that requires the clock reset which could solve some mysteries, but I haven't been able to mount it properly yet as a disk, since I'm running an emulator on my laptop, so I haven't dug into it yet. I have to dig out an old Windows laptop to get looking into it.

British - good attitude and glad you feel this way. I too try to be easy going when I start threads and don't sweat "topic drift". In fact, I encourage it. This Bentley site is very tame and small with not that much activity. I belong to several other sites, some of which are huge (thousands of members) and all threads drift. Just the nature of spontaneous online chat. For me it means even more new information, challenge, chat, and adds to our collective knowledge....all good stuff!

Back on topic - You've received a lot of suggestions here, some that will get you fixed and some that are good preventative maintenance items. At this point, I think you can choose whether to get directly at the issues causing the CELs and call it a day or combine it with some good maintenance tips too. If you decide to go directly at it, then go directly to the EGT sensor on the passenger's side, bank 1. These EGTs are the better part of $300 just for the sensor and not a good use of funds replacing the wrong one and still end up with a P0545.

On this site, and it is the nature of this car with its complex electronics and somewhat suspicious location of sensitive computer modules, it is common by many members to recommend removing, inspecting, cleaning and replacing electronic connectors, especially at the two ECUs. Well, there is good news and some bad about that. While the inspection and maintenance is a good thing, most do not have a very deep understanding of complex electronics and most do not understand the nature of static electricity and the devastating effects it can have, usually with the layperson not realizing that damage was done.

Static electric shock (which is often transferred from your hands via touching connectors on computers and harness connectors) can destroy an ECU in less than an instant...and you'll never know it until you try to start up. I've had both my ECUs out of my car along with all of the connectors in the vicinity unplugged, but I ALWAYS have a grounded wrist strap on, especially here in Arizona where humidity is often in the single digits. I've spent my life as an Engineer in the computer/electronics industries, and I've lived half my life wearing a ground strap. So, if you decide to add the extra steps and time to remove the cowl and tackle the electronics in the right hand corner which is good advice, some caution for you as well.

Static Electricity to a computer is like Kryptonite to Superman! If you do not wear a ground strap, at least do not "paw" the connector ends either on the harnesses or the modules. Try touching metal to ground first as if you've built up SE in your body discharging it right before touching the ECU increases your odds.