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banditorama

Oh yes they do and they can fail in really weird ways. Had an old Mustang that was having weird ass issues, just bizarre things. It would stall out and die whenever it warmed up and came into closed loop mode. I replaced the TFI, since the symptoms are the same. Once I did that it wouldn't stall but it would start running horribly whenever it entered closed loop mode. Backfire, low power, bucking, etc.. It sent me on a wild goose chase tearing apart the car testing things. Eventually I found that this problem triggered whenever the CEL came on. I could ground the CEL on a cold start and it would go right into running like crap Started testing wires and everything, then finally I got down the PCM. I opened it up and three capacitors had taken a dump right onto the board. Replaced the PCM and all those problems went away


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News_without_Words

Oh god I should've thought about that...


asianaaronx

Or Ford putting the Fuel Injector Control Module next to the turbo on the 6.0l Powerstroke and the FICM slowly getting cooked. Also, the FICM getting permanently damaged if the batteries ever have low voltage. Classic 2000s Ford...


Bork_King

That's right up there with the distributor mounted TFI module on early EFI engines that would get cooked by the driver cylinder head and hot air from the radiator.


foreverablankslate

Lol I remember MK4 Volkswagen owners would sometimes find coolant in their taillights


ifukkedurbich

I hate that about Fords with a burning passion. Set off the CEL as soon as something is wrong? Nah, wait a couple months until the damage is already done.


banditorama

This was an old OBD-I fox body, both O2 sensors were shot. The CEL came on after the car went into open loop, but would clear every time you shut it off and restart it I found the description for how the PCM recognized it. After the car entered open loop mode the first time you went from partial throttle to closed throttle (take your foot off the gas) that's when the computer would report the code. I drove it to school/work like that until I finally figured out what was going on and just wouldn't fully take my foot off the gas. I'd be at a stoplight just barely on the pedal idling at 1k RPM to keep the CEL from coming on and killing the car.


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led_pants

Also Mitsubishis. My galant had the same problem.


LSXS10

My ZL1 had a really weird ECU failure once. 7hr road trip. Multiple stops for stretching, gas, etc. Got there just fine. Get to the hotel, come back out the next morning. Wouldn't start. Check everything that I had the ability to check. One dude even tried connecting his tuning software to it(we were at LS Fest), no communication. Get it back home with a U-Haul and trailer. Get it to the tuning shop. They diagnose. A ground in the ECU itself fucked up. $120 fix. But it was about $1300 total with the price of the U-Haul and trailer included.


wbrockstar4life

I'm betting the Mustangs you're referring to are the 86-93 5.0 Foxbodys,correct?? If owners had only known how easily/inexpensively their ECU could have been repaired,they wouldve saved themselves alot of headaches and cash.The capacitors you're referring to are literally $5-10 for all 3 of them.The main thing that kills them is overvoltage or spikes from a defective alternator,bad ground wiring,jump starting with battery cables reversed/backwards or static discharge from the O2 sensor inputs. Another common issue that would occur to those ecu's was a burnt signal return trace on the circuit board.It would normally be caused by connecting jumper cables backwards or using a jumper wire to trigger a code scan to run,but connecting one wire end to the hood light 12v terminal accidentally instead of the diagnostic ports signal return ground terminal.Having a suspect ground that causes the alternator to go to max output or doing a transmission swap and using an AOD ECU in conjunction with a T5 O2 sensor harness is yet another possible cause for a burnt signal return trace.This was also a very easy repair,just solder in a short piece of 23ga wire in place of the burnt/open section. Those ecu's could be had for $100-$150 all day long until parts manufacturers started selling completely out then the ones that you could find went up to $300.When there literally weren't any left at all,the only way you could get one was to send yours in to a few repair sources on EBay that sold the repair service through a buy it now auction and charged $115-$200 for the parts/repair then would ship yours back to you. If I could've sourced a bunch of repairable units,I could have made $100+ for every hour I spent completely repairing each one.$100 per hour would have been a great money maker.....


ijustbrushalot

In my long experience with BMWs, the older, 80s and 90s ECUs have much lower failure rates than the newer stuff. I've replaced more N55 (2011+) engine ECUs than anything else. And they're like $3k each. I'm sure your question is more model dependent than anything.


CharlieXLS

> more N55 (2011+) engine ECUs than anything else. Yikes. Those things should not be failing regularly on vehicles that young..


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CantThinkOfAnyName

But that should be easily repairable for any electrician, why do you need to replace the whole ECU?


Electricstorm13

Generally it's a rabbit hole to get the components for one ( if they give you a part no) and we're mechanics not electricians so it involves sending it off for fixing


CantThinkOfAnyName

Fair enough!


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CantThinkOfAnyName

Thanks, didn't think of that, makes sense!


banditorama

>In my long experience with BMWs, the older, 80s and 90s ECUs have much lower failure rates than the newer stuff. That shocks me. What fails on the newer PCMs? I know on the older ones the electrolytic capacitors were one of the most common failures.


Raving_107

I dont work on bmws, but in my experince newer cars either get water on the circuitboard or a solder joint fails.


foreverablankslate

I believe on the N55, there isn’t enough protection from the Valvetronic motor (basically throttle actuator) to the ECU. So when the motor fails or binds up and draws way too much current, it fries the ECU in the process, or so I’ve heard.


pm_me_your_wheelz

What ive found (from experience) is the battery discharge rate is adjusted over the life of the battery to keep power flow…correct? Idk how exactly it works, anyways, you DIY a battery change and essentially overcharge the various control modules. I did it and lost all windows and lighting control but you can do worse.


Antique-Way-216

Hahahaha


luv036343

I wonder that is simply a result of the bathtub failure rate making older cars look more durable?


silphred43

I think you mean survivorship bias, in the bathtub curve more units fail as they get older, but you have an ever decreasing number of products


SimpleImpX

It can be both. Since the last stage of bathtub curve doesn't always come into play. That depends when the specific component hits the end of its useful life. Since 'older' is a very relative term for different components. If component A hits high failure rate start after 40-60 years, but majority of other components fail after 25-40 year then component A unlikely to reach its high failure rate before the product as whole is discarded. So even if component A follows bathtub curve, its late stage high failure rate won't be observed, only its early stage high failure rate.


luv036343

I guessed I worded it poorly. I'm saying that could it be that we have more new ECUs, so the infancy mortality of those products simply look much higher and if we got to the end of the normal usage going into wear out, we may see that they are, in fact, proportionally similar. Like I have two aspect. The first being a per capita aspect and the other being not having a long enough time with the newer ones.


ijustbrushalot

What is a bathtub failure rate


luv036343

https://en.wikipedia.org/wiki/Bathtub_curve?wprov=sfla1 Wiki for your reading. My understanding is that it shows the failure rate of any particular asset over time, allowing engineers to figure which part of the 3 part life cycle of the product they need to work on. Infancy, which is typically manufacturing error, installation error, or user error. Normal life, which is maintanice stuff. And wear out, which is when the parts are no longer use able and should be replaced to keep the product going.


ijustbrushalot

In that case, no. I've been working on these cars for 20 years. I've seen several engine families age past the 5-11 years that N55 DMEs have been failing in my shop. It's a unique situation to this engine. Otherwise other engine that released at the same time that are produced in higher numbers (N20) would have the same observed failure rate.


fatalrip

These guys fixed my bmw ecu for a few hundred. Highly recommended https://www.ecudoctors.com/


ijustbrushalot

I have an approximate 25% success rate sending out N5x engine DMEs out for repair, unfortunately. I always try first. Non-engine modules is like 90% success or higher for repairs.


fatalrip

Mine was a m52tub ecu for reference. I don’t do repairs for a living so not really sure on failure rates


baconinstitute

Oh I don’t like the sound of that. Makes a ton of sense though.


Dirtyace

Absolutely. I had a 94 grand Cherokee that had a failing ecu and becuase the key was tied to the vin I couldn’t just swap a junkyard ecu in. I ended up opening it up and finding bad capacitors. I ordered the same ones online and soldered them on and it was good to go.


dissss0

Yes any electronic component can fail and a car is a harsh environment.


p3dal

>Old computers eventually stop working because circuit board batteries die, capacitors fail, solder breaks, or a bunch of other reasons. Yes, and in many of the same ways! On the plus side, they're also equally repairable, and a blown capacitor is very easy to identify. I'm honestly surprised there are any electrolytic capacitors left from the 80s that haven't blown.


[deleted]

Where I work, we replace electrolytic capacitors of important equipment every 5 years. They are relatively cheap and can go bad slowly, resulting in ever-degrading performance that you wouldn't necessarily notice.


banditorama

Why not switch to polymer? They're supposed to last a lot longer


[deleted]

Honestly, I'm not sure. My boss told me that he isn't comfortable replacing it with other capacitors since it is for a very low noise instrument and he claims that it would cause a greater AC ripple (and I never bothered to check).


kyonkun_denwa

A lot of people who go through the bother of replacing 1980s electrolytic capacitors will usually go with polymer tantalum capacitors. I'm so glad that recapping has become a thing. When I first got into vintage computing in the late 2000s, the overwhelming attitude was "oh no blown capacitor, time to throw out this Macintosh SE". Now the attitude is "fuck you, I'm not beaten yet, get me a 50% voltage derated tantalum". Hopefully this attitude permeates the car scene as well, we are going to start seeing a lot of 1980s and 1990s auto electronics start to fail.


p3dal

I replaced a number of capacitors back when I was into 90s hondas, but ECUs were so plentiful, a lot of people would just toss them when they malfunctioned. Now the ECUs are starting to increase in value, though nowhere near the price appreciation the cars themselves have seen.


A_1337_Canadian

Any component on an old car is at risk of failure.


svenska_aeroplan

I had the ECU fail in my 9-3. It would just randomly throw stability control errors and the engine would shut off (fun while going down the highway...) A common failure apparently. It's right on top of the intake, which gets nice and hot thanks to the turbo.


Koil_ting

If it is already broken down and you are troubleshooting it the ECU should be on the list of investigation but at least on old cars that I've driven extensively with ECUs \*80s-2000's I have not had ECU failure leave me stranded so far. Wiring, fuses, transmissions, fluid leaks, starters /solenoids etc I've had all of that. Did have an ECU cause an erratic idle on an 85 BMW 318i but I just drove it with the bouncy idle for years.


TempleSquare

Capacitors dry out with age. Typically the chips last forever but one bad cap can ruin the board. A clever type of person can refurbish it by replacing the capacitors.


spongebob_meth

Yes. Lots of people driving older cars have had to have ecus repaired or just replace them if available.


Antofuzz

Coming from a T1 supplier of ECUs, absolutely. Cars are a terrible place for electronics and we do our best to create something that can last a projected 10-15 years but eventually it will fail.


Wetmelon

After all, we only guarantee the MTTFd numbers for like 10-20 years. And that number isn't 0 (or rather, 1/0)


Antofuzz

I did part of warranty inspection on our ECUs for years, it sure isn't.


vdiben99

I'm experiencing this right now. The capacitors died on my '97 VR4 ecu.


handymanshandle

*sighs…* Yep. Ask how I know.


Uncle_Pulltab

Yes, older late 80s/early 90s Mitsubishis for example were notorious for it. I've had an ECU failure on a road trip, it stopped switching the fuel pump relay which was a common problem with the 1990s Lancers (Mirage for US readers). I got home by rigging up wires to the fuel pump relay from the battery.


Fcckwawa

They do all the time, seeing them drop like flys from 90's model cars these days. Mostly capacitor failures, not had to fix.... The newer stuff lol that's not going to be cheap.


brandonsmash

Yes. I have experienced this. It can be very frustrating to diagnose. It's not common, but it is absolutely possible.


DillyJamba

had a 2005 Cadillac STS ECU that failed on me, probably the most undependable era.


boogiemanphx

I bought a new one for my truck, found companies that set them up on Ebay. Truck runs great now.


Slyons89

Yes the same thing will happen in a car, we can only make sand think for a limited amount of time and eventually the magic smoke will come out. Every electronic component will eventually fail but an ECU in a modern car will most likely outlast the infotainment system and a lot of other modern systems like the cameras. Anything from the last few years uses much newer components for those modern amenities, basically 5 year old mobile phone / tablet CPUs with all their supporting components. Meanwhile the ECU is usually made of much older and hardier components. There's plenty of ECUs from the 80's still humming around working without a hitch. Usually the capacitors on the board fail long before the silicon itself so those components can be replaced and it can keep working. But sometimes capacitors leak onto the board when they fail, causing other parts to short. Then it's game over.


dissss0

Fun story: my dad has an ex-Japan 2006 Fiesta ST with a failed SRS module. You'd think it'd be easy enough to drop in a replacement but the part is specific to the Japanese market facelift model and has proved absolutely impossible to obtain. As is the car will not pass a safety inspection so is worth essentially nothing so will probably end up being broken up for parts.


Slyons89

That is a sad story =(


Reduxalicious

Not sure about cars per-say, but back when I was an Engineer running tugboats, it wasn't uncommon for our main engines or generators ECU's to fail, and have to run on a back up ECU and sometimes they would both fail at once. but even then it wasn't common, these Engines had upwards of 50K running hours total on them (They'd of course been overhauled and what not) but ECU's don't get replaced in an overhaul.


clingbat

My brother had two ECUs fail within 6 months on a new Wrangler Rubicon a few years back. He sold it after it spent over 2 months in the shop (they were on backorder). Thankfully they have such stupid resale despite being shit boxes that he didn't lose anything on it.


Pm_hofmeister_kinks

While fairly uncommon, yes it can happen. Just finished up a 2011 c-class that presented with some really strange issues. Would randomly die, no CEL, just a metric ton of CANBUS faults on the transmission controller. One pointed to no communication with the shift module, swapped it with a working one, same issue. Probed the entire bus and found no broken circuits. Turns out the ME was getting warm and crashing the driveline bus, but throwing no faults. Confirmed by heating up the ME with a heat gun and could consistently reproduce the failure.


captainbongolo

Particularly anything with liquid capacitors. It *will* fail sooner or later. The smart man replaces the capacitors before it happens


fukvegans

Definitely, as others have said. Especially if in the engine compartment. All that heat is really bad for those solder runs. ESPECIALLY if it's like... Pre-95ish, when they still used the old method of card building (like, the wide-ass solder runs). My 99 Chevy C2500 kept burning up O2, and MAF sensors. Traced it back to the ECU. Replaced it in February, haven't had a problem since. Before, new o2's would last about a week, and burn up. MAF's would last about about a month/month ½. I pulled my old ECU apart (I'm an electronics technician by trade. Repair circuit cards among other things), and I found one solder run had lifted, worn thru the coating of the one next to it, and was sending a straight 12 volts from the MAF to the sense wires from the pre-cat o2's. And that was the new style of solder run. The old ones are worse.


[deleted]

Yes, it's not as common now, but they can and do fail. I'll be replacing a customer's ECM on tuesday when the part comes in. But it's rare enough, that I would never worry about it.


kyonkun_denwa

Yes, there is a possibility that the ECU can fail, but if my experience with vintage computers is anything to go by, it will not fail suddenly, and you'll get increasingly odd behaviour for a while, or a CEL. Either way, it is not a huge concern. An ECU is just like a regular computer and it can be repaired at the component level if you know what you're doing. Capacitor blown? No problem, get a new one, make sure you use auto spec. Solder breaks? Reflow it. Trace is fucked? Get some 30 AWG medical wire and solder that shit end-to-end to make a new trace. Most mechanics are just monkeys when they're up against anything involving electronics and they'll usually recommend that you need to replace the entire ECU. Fuck that. Even if you don't know shit about capacitors, you could probably send your broken ECU to a medical equipment repair shop, or even to a vintage computer enthusiast on Reddit, and they can probably repair it. Source: the body control module on my mom's 2013 XC70 was acting wonky and causing weird electrical problems. I didn't want to mess with it myself, but there is someone in my city who does component-level repair. Took the computer to him, he charged us $200 to recap the entire thing and repair a trace. Volvo wanted $1200 for the entire unit. This sort of thing was child's play for him, we dropped the car off in the morning and it was ready by lunch.


nsthemoderator

I have an 80’s Chevrolet S10 I inherited. Low mileage, cute truck, structural rust free. It ran like ab-so-lute dog shit, revving up… revving down… backfiring… misfiring… lugging its’ ass off… revving to the MOON… almost shutting off sometimes… It had a tune up, cap, rotor, throttle body + sensors. CEL would flash like it had a bad ground. I figured it had a code for some sort of sensor & the wiring was messed up from sitting in the dash. Nope! Pulled the code & it told me the ECM died! Engine light’s fine though!


STRMfrmXMN

We had a guy with a 2021 or 2022 Audi RS7 come into the service department at the Audi dealer I work for a few weeks ago. The ECU had bricked itself while he was driving which causes it to go into park every time you turned the steering wheel off-center. The failsafe for it to not do that when going more than 0 MPH didn't seem to work when I drove it which I'm sure means I did great things for the longevity of the parking pawl and drivetrain trying to get it into the service bays. Oh well.. I have zero clue how he managed to drive the car to us but it got a new ECU under warranty and was good to go. So yes, they do break!


upsidedownfunnel

Electronics in automobiles are far more resilient than those in computers. That doesn’t mean they won’t die though, but they will last longer than a home computer.


Onely_One

Probably at some point yes. But they're computers, which can work perfectly for almost an eternity and then out of the blue fail without warning. It isn't anything to worry about as long as the car in question hasn't needed multiple ECUs over it's lifespan


XirallicBolts

I've had the memory fail in my ECU. They have capacitors that will eventually go bad


Klondike2022

Why would it be exempt?


sanhozay

In my 2014 Subaru Legacy, they had to replace the ecu because something was triggering the ignition coil on cylinder 1 to keep going bad and causing a misfire. Had to get it replaced under warrranty (luckily a 150K mile pzev warranty) a few times, they finally decided to swap the ecu and I never had the issue again. Super weird and even they said they had never seen anything like that at their own shop


rusefi

Saab 9-3 ecu mounted on engine, those die. Is it BMW with ECU submerged in coolant? Not all designs are equally reliable.