Dishwasher Repair Nightmare: Chasing Down 3 Faults

It all started with a vague error code (shown in the image above) on [nophead]’s Bosch SMS88TW01G/01 dishwasher, and it touched off a months-long repair nightmare that even involved a logic analyzer. [nophead] is normally able to handily diagnose and repair electronic appliances, but this time he had no idea what he was in for.

Not many dishwashers require breaking out a logic analyzer and 3D-printed custom adapters, but this one did.

Not only were three separate and unrelated faults at play (one of them misrepresented as a communications error that caused a lot of head-scratching) but to top it all off, the machine is just not very repair-friendly. The Bosch device utilized components which are not easily accessible. In the end [nophead] prevailed, but it truly was a nightmare repair of the highest order. So what went wrong?

One error appears to have been due to a manufacturing problem. While reverse-engineering the electronics in the appliance, [nophead] noticed a surface-mounted transistor that looked crooked. It was loose to the touch and fell into pieces when he attempted to desolder it. This part was responsible for switching an optical sensor, so that was one problem solved.

Another issue was a “communications error”. This actually came down to ground leakage due to a corroded and faulty heater, and to say that it was a pain to access is an understatement. Accessing this part requires the machine to be turned upside down, because the only way to get to it is by removing the base of the dishwasher, which itself requires a bizarre series of awkward and unintuitive steps to remove. Oh, and prior to turning the machine upside down, one has to purge the sump pump, which required a 3D-printed adapter… and the list goes on.

And the E02 error code, the thing that started it all? This was solved early in troubleshooting by changing a resistor value by a tiny amount. [nophead] is perfectly aware that this fix makes no sense, but perhaps it was in fact related to the ground leakage problem caused by the corroded heater. It may return to haunt the future, but in the meantime, the machine seems happy.

It goes to show that even though every fault has a cause and a reason, sometimes they are far from clear or accessible, and the road to repair is just a long slog. Heck, even phones these days can be bricked by accidentally swapping a 1.3 mm screw for a 1.2 mm screw.

42 thoughts on “Dishwasher Repair Nightmare: Chasing Down 3 Faults

  1. Just a word of caution: Before messing around with scopes, logic analyzers and stuff like this make sure your device has proper separation from mains and that GND is really GND/PE!!! Some appliances might use capacitive droppers or have weird voltages between the local “GND” and the PE (to with the GND of your scope and your computer is connected). Be careful with this or you can fry lots of expensive stuff, including yourself.

    1. Good point. All the “computer/low voltage” parts on our IKEA (rebranded big-brand machine which name escapes me right now) diswasher is very much not isolated from the mains. Since the appliance is double insulated and grounded there is no incentive to insulate it.

      1. the escaped name could be Whirlpool, the manufacturer of some low-quality IKEA dishwashers.
        Mine had more than one of these leakages caused by leaking water from the dishwasher chamber into the base this caused by insufficient detergent. Useless to say that the teardown of such home devices is a mess.

  2. Good on for him for persistence. Ive had my 20y/o F+P DD603 apart more times than I can count. $2200 for a new one, no thanks! Fisher and Paykel gear seems to have maintenance in mind as a design consideration, all you need is a screwdriver and pliers. Plus I have the service manual which wasnt hard to find online.

    1. Interesting. Bosch dishwashers are the top rated by Consumers Reports and have the highest 5/5 predicted reliability. Looks like this guy was a victim of the low end of the bell curve or got a particularly poorly designed model.

      1. Reliability is a very different thing from repairability, a 5/5 rating for one doesn’t me the experience will be good if you need the other. So I would say this is an awful model, and likely everything the company has made around the same time period will also be. It just doesn’t go wrong as often as some of the probably much cheaper and properly maintainable/repairable models that only get 4.5/5.

  3. I hate Bosch appliances. We bought a new-built home ~10 years ago with a kitchen outfitted with Bosch appliances. A month after moving in the overhead microwave quit working. Mother-in-law was heating up something and opened the door. There was a pop and a small flash and it was dead. Builder came in, checked the wiring (found no faults) and replaced it. Worked for another month or two then the same thing happened. By then the builder was off on another project but sent a rep to take a look. They had no more but told us it was still under manufacturers warranty. Just give Bosch a call. Bosch passed us off to their local support contractor who told us that our model was no longer manufactured. They could get parts but it would take a while to get them. We had them make the order and bought a cheap ($70) counter top microwave from Target to get by. The parts arrived a month later, repair guy comes out and does his thing. Microwave seems to be working. A couple of weeks later, flash/pop. Dead microwave. I call the Bosch contractor again and am told they can order me some new parts. Same wait time. I told ’em not to bother. I went to a local appliance store, bought an inexpensive Samsung model, and had it installed. Today both the Samsung and the cheap Target microwave are still working.

    What do we say about Bosch, Raymond? Bosch sucks.

  4. Good to see Nophead still doing interesting work and posting it.

    Early days in Reprap his work and testing really helped influence and guide quite a bit of what I was doing (along with #reprap@freenode of course).

    Sidenote: I need to do some similar reverse engineering on a Bosch dishwasher…attempting to disable the heating without causing errors.

      1. Not looking for errors…trying to disable the heat part of the cycle. I can easily cut the heater wire…but I suspect that will trigger issues.
        I converted a dishwasher to a recirculating DI wash for PCBs…but I have to use the short cycle and/or watch it to avoid the heat cycle.
        I found some pushbutton codes for another model that claimed the ability to disable using some sort of front panel Konami code…but I haven’t figured it out yet.

        1. It probably doesn’t measure the heater current, but just the water temperature, and if it doesn’t reach the setpoint temperature within the expected time it would flag an error.

          An easy hack could be to use a resistor (value to be determined) mounted directly to the temperature sensor, out of the water, and disconnect the heater.

          1. I was debating that too.
            My concern was that it could also have a watchdog tracking expected rise time and if there was “no change” it would flag as well.

            List of possible issues that could come up…but I haven’t tested anything yet. Much easier at this point to just hit the short wash 2 times :)

            At this point I likely won’t get around to messing with it until I end up taking it out of the enclosure to do other work. I was thinking about talking with the local appliance parts supplier to see if they had access to any special manuals with a more clear button press sequence.

          1. I suppose I could do that too…wouldn’t be too bad…it was my initial thought. Just drain, fill and pump on/off if I eliminate the whole heating thing…but at the same time the easiest method was to attempt to just turn off the heating (if it can be done via buttons).

  5. Some error codes are hidden from normal view and are accessed by holding buttons on startup. The pump/heater may be removable without turning upside down from the bottom. If you can get your arm in you can pull it out the side once the controller PCB is removed. Mine failed to get hot so based on internet assumed it was the relays. Nope, it was the propeller breaking off the waste pump which the dishwasher detected as in sufficient water flow in the heater. I repaired that with epoxy that worked surprisingly well, but in doing so created a small leak(heater pump is only clipped together) that after a few months caused the element to fail. I non genuine pump was fitted that then caused more problems as u think the NTC was slightly different or something, it was enough for it to give up heating the water sometimes. But Yet again, the error code was hidden and if you didnt know it looked like it completed its wash with no problems, except dishs dirty and water not very hot. A genuine pump has solved that now!

  6. Our Bosch dishwasher wasn’t starting. I’d gotten used to looking up the error codes, which usually came down to removing some debris from the pump or drain hose. This time, it was showing code “H:04”, which I couldn’t find in the manual or online. Wasted an hour or so before I discovered that meant a four hour delayed start. :)

  7. My NEFF (Same company as Bosch/Siemens) electric hob broke. A new one is > £1000 (US$1200) as it is “non-standard” size.

    The hob would just flash “-“‘s in the control panel indicators.

    Wife said “just get a new one” – which to me sounded like “Darling please repair it if possible”

    A “new” replacement main board was about £280 ($330’ish) – and the main board is rather basic. If you add an installer coming out – it would have been another £60-£80 in callout plus 1 hour labour @ £60-100 – so roughly £500.

    So I took it apart – and looked for the telltale signs of capacitor issues. And bingo – one slightly swollen capacitor. I did not have a similar one in the parts bin – but found one locally – and put in a replacement – and hey presto – the NEFF was working like a charm again. Actually much better than before – so the cap has obviously been a problem for some time. The original capacitor was “ok” spec-wise but not what I would have chosen for something that gets so hot for so many hours. And I would have chosen a better brand.

    So if your operation of a NEFF/Bosch/Siemens Hob starts to feel “sluggish” is is probably a capacitor issue. But a £0.35 capacitor can fix it. For details and “forget-me-not” the repair is described on EEVBlog forum.

  8. Recently, after some power outage issues, our Bosch oven wasn’t working. Fortunately I was able to whip out my new $58 portable o-scope (ZEEWEII DSO1511G) and debug it, after finding the factory maintenance and trouble shooting manual. The maintenance manual guide for testing signals between boards was “look for voltage drop to 4.7v every 2 seconds with a multi-meter”, but it’s much easier to confirm data signals with the o-scope.

    The o-scope certainly paid for itself on that one repair.

  9. Ugh, I echo the sentiments of MW, but only when it comes to dishwashers.
    We had a Bosch dishwasher that went wrong. It would try to fill, error lights would come on, which pointed at a particular part of the water inlet system. I bypassed the fill sensors to check whether they were the problem, and one of them appeared to be faulty but was completely integrated into the assembly.
    The particular part that was defective was going to cost half the total price we had paid for the dishwasher as new, so I scrapped the damned thing and bought a different, non-Bosch one for a lot less, and so far, *touch wood*, it is running just dandy.
    If only companies would standardize their parts, but their excuse would probably be that it would stifle innovation. It would mean they couldn’t screw their customers out of a load more money more like.
    Bosch DIY tools are very good value for money though.

  10. I bought my condenser dryer back in 2008, bought the cheapest I could get: a Beko, made in Turkey. I did have to change the mains filter once (£10 on eBay, which wasn’t even the exact correct part but for mains filtering does the job fine), and it’s still running today.
    Same with dishwasher, cheapest I could get was an Indesit. About 1/3rd of the price of a Bosch, it’s now close to 10 years old and also still going.
    Yes, Bosch/Miele may have changeable parts such as bearings, but they are a pain to change, and the spares are vastly overpriced anyway.
    I’m still in favour of people who can spare the cash to go for Miele/Bosch if it means less appliances ending in a landfill, but for the average Joe like me not living in a mansion with a garage full of luxury cars, buying a more reasonably priced appliance and taking care of it (e.g. maintaining it, such as cleaning filters, and not abusing it such as heavy unbalanced loads) always served me well.

  11. I have an lcd display from that model which was pulled out when the machine was scrapped. I’ve been unable to find how to control it as it appears to be a serial display. Only 6 pins on the display module itself which has some controller on it as well.

    If anyone has the pinouts for the display I’d be interested in seeing them.

      1. Not really, no. There’s only 3 pins used on that 6 pin connector as they are mirrored on the other side of the board. It’s simply ground, power and data. Looking at Nophead’s article it’s some sort of one wire serial interface which would be more hassle than it’s worth trying to reverse engineer it.

  12. Having formerly been a bosch authorized servicer, and having no love for the stuff they are making now, this one in particular had issues with the heat pump (yes, that is what it’s called) probably has a burned trace on it, checking resistance will settle that. A lot of the time, it has a sensor that reads temperature changes, and if it doesn’t read them, it assumes there is a problem and doesn’t go beyond that to help. Smart appliances are rarely that smart.
    Oh, and 3d printing an adapter to drain the dishwasher? Dude, just hook a wet dry vac up to the drain line and let it go to town, lay a towel down to catch any dribbles and your golden.
    It typically took me about an hour to replace a pump, start to finish.

    1. As an appliance tech, I question what has been going on with Bosch designs lately… they have a “Crystal Dry” system that uses a separate compartment and heater for drying(along with Zeolite moisture absorbing crystals). That thing is a pain… it either leaks, fails because of water in the container, or makes a burning smell after a few months. They are so hard to remove that Bosch has a custom built kit to jack up the tub away from the base. Cool to learn why the pcb went bad. We regularly replace the heat pumps with the main pcb. I tend to recommend Bosch for the good customer service they provide. But if reliability on their newer models (looking at you Thermador pro ranges) keeps declining I might have to find a new company to recommend. And Aztraph is absolutely correct about water and heat pump removal.

  13. I recently repaired a dishwasher with a failed “heat pump”. Quite Interesting design. Instead of having a “classic” heater element, the pump housing itself is the heater. A stainless steel ring with a flexible PCB heating element wrapped/glued around it. There was no sign of a fault, but there was no continuity (well, it should be about 19 Ohms). Turned out, the trace broke/burnt right unter the plug…

    It’d be nice if you could get the heater ring separately, so you don’t have to throw away the otherwise perfectly fine pump (it’s a BLDC motor!)…

  14. Bosch dishwashers and electronics.
    There was a problem a few years ago, that they tended to catch fire. This was due to a print relay that got hot and desoldered itself, then the bad contact on the pcb got hot and sometimes caused a fire.
    As workaround the Bosch service came and added a second relay, so that the original one only had to switch on a relay and had no load itself.
    Of course the workaround relay also was too small and got too hot. But it didn’t unsolder itself it just stopped working and caused no fire.

    I think that is a good example for the quality of electronics in Bosch dishwashers.

  15. “They’re all made in the same factory in China”. Not necessarily true, but go to a bib box store and look at the different brands side by side, and there are some remarkable similarities. All the icemaker look like they come from the same company.

    I have a Bosch dishwasher, and it’s been pretty trouble free. Nice stainless interior, which is what sold me. I think I have had it around 10 years, so definitely on the downslope now. Have had two issues with my Bosch refrigerator: the 3-phase motor drive unit failed (it’s generic and easily replaceable, but I didn’t know that), probably due to a powerline transient, and the defrost heater coil for the main compartment failed (age, apparently).

    Bosch used to be a premium brand, but they appear to have lowered their cost as time went on. At least they seem to be a bit better designed than GE or Whirlpool.

    1. About 30yr ago we had a school excursion to the Phillips factory for video cassette recorders in Vienna. They proudly presented a rack with different VCR front panels for different brands. About 20-50 brands bought the VCRs from that same factory, at that time not in China but in Austria.

  16. I had a friend with a Bosch D/W. She had the ultimate repair fix. She had a $120 a year maintenance contract. The board was replaced at least 3 times and other parts too. Genius. Remember when the most complicated part on washers, dryers and dishwashers was the rotary mechanical timer.

  17. Bosch giống như TOYOTA nhưng khác với hảng xe Nhật BOSCH để lại một số khiếm khuyết từ kiến trúc xây dựng trong đó heating pump là một điển hình

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