[DGO]

Got in the car to drive today, on starting the wipers came on (even though they were switched off) the central locking from the key fob doesn't work and I got error codes for the ACC, FCM and Service HID. Scanned for Codes and am getting U0104 Lost Communication with Cruise Control Module, U0121 Lost Communication with ABS module and U0212 Lost Communication with SCM

Hoping someone has an idea where to start to find the issue here

Thanks

 

[devilmaycare]

Multiple error codes have often been the result of a chaffed harness in the OM642 engine, but can't comment on the FIAT CRD. Another possible cause is low battery volts. Are your battery and alternator OK?

 

[DGO]

Thanks for your thoughts. Battery fully charged. I'll run an alternator test at the weekend.

As far as I can see the Fiat engine doesn't suffer from the wiring issue on the aircon pipe

Has been suggested to me that the connections to the front fuse box/earths at the front might be a problem. Has been snowing and raining here since I last used the car and suddenly I have issues

 

[CtCarl]

When I've seen that many lost communications messages, the most common issue has been a power fault; either a borderline battery or alternator, or loose, dirty or corroded ground connections, often at the rear of the engine block/heads, or the main ground post in the front of the engine compartment near the "jump start" post (on US models).

 

[DGO]

Well I had half an hour to have a quick look this morning. With the faults there are more issues than I had found initially. Indicators, screen washers, door unlocking from the fob (I'll replace the battery in case) and high beam don't work - but the doors do unlock and lock with the touch function.
1. I checked all the fuses in the front fuse box - all were OK and the fusebox is dry
2. I "wiggled" (technical term) all the relays to make sure they're seated. Do the relays just pull out?
3. I found 3 earth points, 2 just in front of the fusebox and the jump start one. The latter looked a bit corroded, I cleaned and tightened all 3. The main power at the front under the red cover is also clean and tight
4. I checked the rear fusebox and battery. It's dry there too but I didn't get a chance to check all the terminals and body earth connections yet

Started the car but no better. Had another thought and pressed the ignition "on" (press button start on my car) without my foot on the brake pedal and left it for a while until all the checks stopped and then started the car - success for now at least.

So there are some more things I will be doing, hopefully at the weekend:
1. Does anyone know where the main engine earth is on Gen 2 cars?
2. Is the HID earth still in the same place behind the grill at the front of the engine compartment? Might have to take the bumper off and check everything under there
3. I need to have a look under the fusebox in case there are any more connections underneath
4. Battery and alternator test to run - my code reader has a specific function to test this
5. I'll check the connections in rear fusebox and the battery at the back of the car too.

 

[CtCarl]

Yes, the relays pull out. If one is suspect, you can swap it with another, although they're fairly inexpensive to replace.

Not sure about your engine, but for what its worth, on Hemi cars, there is an earth/ground connection at the rear of each cylinder head.

 

[DGO]

Thanks. I will try swapping some of the relays around and check the terminals aren't corroded. I'll see it I can setup a way to test them too

Will have a search around the engine for the earths, first time I've had to crawl around the VM Motori diesel

Thanks for your help so far

 

[2015Chrysler300c]

I had similliar codes thrown with my 2nd gen 300. I did pretty much the same things you are doing. Any chance that an abs speed sensor fault code was listed? That was what my problem. I couldn't belive the wipers initiated because of a failed speed sensor. But.....

Let us know what you find to be the problem.

 

[DGO]

Only the 3 codes I listed unfortunately UO104 (Cruise), U0121 (ABS) and U0212 (SCCM). Definitely seems like a power or communication problem to me, given it just suddenly happened

 

[CtCarl]

Glad to be of help.

I don't know if there is any possibility of shipping these to the UK, but the reason I mention it is that they're small and light, and every now and then I make a purchase on that auction website or that other big website named after a river in South America, and it's shipped from England and yet, is still competitively priced.

This is just an example of a Chrysler powertrain plug-in relay. It sells for US $6.78, which is around £5.



Good luck!

 

[DGO]

Well just maybe....

After several hours checking relays and fuses front and back, followed by disconnecting the battery to reset the systems in the car, checking the earths at the back of the car by the battery and the rear fusebox. Each time no further progress, still No ACC, no FCW though somehow I have managed to clear the wiper and indicator problem (sort of).

So by mid-afternoon yesterday I was thinking I must check the ACC sensor as that's used in both the cruise and front collision system (I believe that's very expensive to replace). So I looked for it behind the grill where it is on Gen 1 without luck. Thought I might end up having to pull the front bumper off next weekend 🙁

Anyway after some internet searching I found the sensor, it's inside the black dome down next to the front fog light. Mine had a piece of leaf stalk about 4 inches long wedged in the slot and sticking across the front of the sensor slightly off centre. There's a horisontal slot to let water drain off the front of the sensor housing (guess it needs that being sealed and so low down on the car). It looks like I must have picked up debris in the rain last week. Pulled the stalk out and cleaned the outside of the sensor housing. Since I did that I have tried the car several times yesterday and this morning - so far no issues at all

It would be mad, but just possibly understandable, if that was the cause. I'm wondering whether, as the sensor goes through its checks when the ignition is first turned on, it was getting a confusing signal and causing the car to throw codes.

Still need to do the alternator and battery check and to rescan for codes but so far so good!!

 

[devilmaycare]

I had similliar codes thrown with my 2nd gen 300. I did pretty much the same things you are doing. Any chance that an abs speed sensor fault code was listed? That was what my problem. I couldn't belive the wipers initiated because of a failed speed sensor. But.....

Let us know what you find to be the problem.

We had one member a few years ago when his immobiliser packed up due to a TPM sensor fault:

Immobiliser fault

Hi, Well yesterday I suffered my first problem with the car, just about to leave for work and the car wouldn't start, not even turn over. So i called the Chrysler Assistance who came out in 90 mins which i thought was pretty good but the bloke didn't have a clue what was wrong, he plugged in...

www.300cforums.com

 

[OzKen]

This is a brilliant post, and well done for diagnosing that.

Amazing how something so simple can be the fault; but if a sensor can't "sense......."?

Great info for others in case they have the same problem.

Well done mate!!!!!

 

[DGO]

I guess it does make sense that failure of a sensor on startup should throw a code but multiple issues being caused by something so simple seems crazy. I guess that's a feature of us driving computers on wheels these days

So far so good, it has been four days and I have used the car each day without the problem reappearing, I was worried I was in for a £1000+ sensor (hope I haven't spoken too soon!).

Going to do another code scan and a battery/alternator test over the weekend. But yes I do hope anyone having a similar problem in future will try cleaning the outside of the sensor housing first!!

 

[OzKen]

I guess it does make sense that failure of a sensor on startup should throw a code but multiple issues being caused by something so simple seems crazy. I guess that's a feature of us driving computers on wheels these days

So far so good, it has been four days and I have used the car each day without the problem reappearing, I was worried I was in for a £1000+ sensor (hope I haven't spoken too soon!).

Going to do another code scan and a battery/alternator test over the weekend. But yes I do hope anyone having a similar problem in future will try cleaning the outside of the sensor housing first!!

Pretty much;

Computer fault finding does it's best to work out what is wrong based on it's preset "list of things it could be."

We had it in it's infancy in 1978 with "fault codes on radar". We never used them; as they were useless, and almost always wrong - THEN.

They are far better now; but to cover EVERY POSSIBLE FAULT/REASON - how big does the list become?

Like when you log on laptop and make password mistake - and it says "system error/can't log you on come back later". It SHOULD say "wrong password." So can be misleading. Some is lazy programming, some is limited memory. But sometimes computer trying to "work it out/draw wrong conclusion from symptoms".

My car did the same when I had the PCV seal fail. It put up a few codes, all related to wrong airflow; but mostly about throttle body and the like. Wanted me to replace throttle body/airflow sensors, etc etc. And it put up two lights (throttle body/ABS) and ABS NOTHING to do with it. It was made more confusing; because it THEN set a very rough idle - to "make sure I'd notice/fix it." Fair enough; (was only unusually long idle period that set it, otherwise wouldn't have noticed) but scared the hell out of me, as seems like major engine management failure.

The "two lights unrelated" thing is probably an "in house dealer code" that the Mopar techs recognise for "manifold leak". But fault code could have just said "manifold leak".

I used a tube in my ear, and could hear it. Fixed seal - perfect.

But brilliant diagnostics on your part. Well done.

 

[DGO]

Well I did speak too soon

Been out this morning and I'm getting U0212 fault (Lost Communication with SCM) again but this time the symptoms are different - This time it's knocking out the instrument panel !

The problem goes as follows:
1. Get in the car and all looks OK.
2. First press of the ignition (ACC), systems start up - all still looks OK
3. Foot on brake and start car - still all seems to be OK
4. About 5 or 6 seconds after the car starts up the instrument panel goes dark - all lights out, speedo and rev counter stop working, EVIC goes blank
Stays blank until the car is switched off - then there's intermittent lights around the speedo and rev counter and the instrument needles twitch even after the car is locked

I've disconnected the battery to see if I can get the systems to reset after an hour or to but this is getting beyond my detective skills now!

 

[devilmaycare]

Has been snowing and raining here since I last used the car and suddenly I have issues

I had a similar problem with the instrument panel/wipers and interior lights, several years ago after hitting flood water at high speed on the motorway. I discovered splash marks on the Front Control Module (FCM) and the problems vanished after the car was left to dry out for a few days.

I don't know if the FIAT engine has a similarly located FCM which could be liable to water ingress - maybe through connectors, but this module does control a lot of functions.

Dash lights like Blackpool illuminations

Hi Hoping some one can offer some advice. The past couple of journeys I've been treated to a 300c light show. There's no lights on at start up, 15mins in to the journey the traction and ESP BAS lights both illuminate with a "ping" and stay on for a few minutes on their own, closely followed...

www.300cforums.com

 

[DGO]

I had a similar problem with the instrument panel/wipers and interior lights, several years ago after hitting flood water at high speed on the motorway. I discovered splash marks on the Front Control Module (FCM) and the problems vanished after the car was left to dry out for a few days.

I don't know if the FIAT engine has a similarly located FCM which could be liable to water ingress - maybe through connectors, but this module does control a lot of functions.

Thanks for your thoughts. I moved the car so it sat in the sun over the last couple of days and guess what - it's working again (for now).

Anyway if that's the fix then I need to do on a water incursion hunt! More fun this weekend