Teardown - Engine Management Computer - Page 1
Forum section: electronics / testgear

author: TerraHertz
author_rank: Super Contributor
timestamp: June 14, 2017, 08:36:57 am
content: A friend's car engine management computer failed, and was replaced. I asked for the old one, to tear apart.So here it is, for anyone interested. This was for a 2001 Astra.Firstly it was surprisingly small.Secondly, hermetically sealed, with no potential for opening non-destructively. It took a vice, cold chisel and hammer to open up. It's like a hard disk construction - diecast case and stainless steel lid, but with the lid rim glued into a slot with a tough rigid epoxy.What really surprised me is the inside. If I'd known what to expect I'd have used a different method of opening it, that didn't produce so many fragments of the epoxy seal.The 'boards' are ceramic wafers, with naked chips wire bonded to pads. All visible because the whole thing is encapsulated with that clear but soft and tacky silicone material. Result: every speck of broken epoxy and metal I created while removing the lid, stuck to the silicone. The worst of them removed with tweezers for the pics. I would NOT want to fall into a pit of this stuff.Very definitely "No user serviceable parts inside."

author: P90
author_rank: Frequent Contributor
timestamp: June 14, 2017, 08:49:14 am
content: I've seen BMW "brains" similar to that.I'm surprised they don't require the old part as a core, like here in US.

author: ManCave
author_rank: Regular Contributor
timestamp: June 14, 2017, 08:50:38 am
content: Is that tantalum cap blown or is it epoxy fragment on it?

author: JPortici
author_rank: Super Contributor
timestamp: June 14, 2017, 08:54:16 am
content: something even smaller: for fiat engines, about same age (and newer).. the whole thing is the size of two fingers. I don't have any laying around at the moment or i'd take a photo. i seriously tought my boss was pulling my leg, as i'm used to way bigger ECUssame wire-bond type of construction

author: tautech
author_rank: Super Contributor
timestamp: June 14, 2017, 08:57:30 am
content: Now you've done it and HAVE TO put up high res pics.Looks cool @ 500% but blurry.

author: sotos
author_rank: Frequent Contributor
timestamp: June 14, 2017, 01:10:53 pm
content: I feel hungry. Please take some more close up photos. If you can.

author: Liteace
author_rank: Regular Contributor
timestamp: June 14, 2017, 01:37:55 pm
content: You can get these open without smashing them, its a bit time consuming but can be done.This model is prone to failure, 99% of the time it's one or more of the link wires with broken aluminium solder joint

author: stj
author_rank: Super Contributor
timestamp: June 14, 2017, 03:40:48 pm
content: you can open many of those by heating them up to soften the sealant.

author: N2IXK
author_rank: Frequent Contributor
timestamp: June 14, 2017, 05:21:58 pm
content: Quote from: P90 on June 14, 2017, 08:49:14 amA core charge would imply that the defective part is rebuildable. That thing really doesn't like like it could be repaired in any kind of economical manner...

author: P90
author_rank: Frequent Contributor
timestamp: June 14, 2017, 07:48:21 pm
content: Quote from: N2IXK on June 14, 2017, 05:21:58 pmThere are many shops here that do nothing but ECU rebuilds. Also, if you buy it from the dealer, they almost always require the old one or charge a core fee.

author: N2IXK
author_rank: Frequent Contributor
timestamp: June 14, 2017, 09:18:05 pm
content: I know that they are usually taken back for rebuild. I replaced one on my vehicle a few years back, and had to return the old one for a substantial core deposit. But that one actually was rebuildable, with standard fiberglass PCBs, conformal coating rather than that silicone gunk, and a case that could be opened without having to smash it. Being an electronics guy, I couldn't help but open the thing up and look for bad solder joints or obviously burnt parts before just swapping the whole thing out.The rebuilder also needed the vehicle VIN number and odometer reading to flash them into the new unit. Apparently, the unit needs to "handshake" with the other modules in the vehicle, and this info needs to match or the vehicle won't start.

author: tmbinc
author_rank: Frequent Contributor
timestamp: June 14, 2017, 09:31:28 pm
content: There's a lot of craptographic handshakes on these kind of devices, yes. I'm glad that the ones I've worked with (various Bosch EDC17, GM E98 and AISIN TCMs these days...) are just standard PCBs. Still a pain to open.

author: TerraHertz
author_rank: Super Contributor
timestamp: June 15, 2017, 02:14:32 pm
content: Quote from: ManCave on June 14, 2017, 08:50:38 amNeither. A couple of the yellow tantalums have what appears to be hand-written felt-tip pen marks, under the silicone sealant.Here's a 2MB image. An original camera image is 5MB, this is cropped and slightly more compression. Appears identical to the eye.http://everist.org/pics/misc/20170615_7362_95.jpg

author: CustomEngineerer
author_rank: Frequent Contributor
timestamp: June 16, 2017, 02:39:57 am
content: Mailbag for microscope fun?

author: TerraHertz
author_rank: Super Contributor
timestamp: June 16, 2017, 09:55:13 pm
content: Quote from: CustomEngineerer on June 16, 2017, 02:39:57 amThat took me a few moments to figure out what you meant.But I have a good microscope. Does anyone want even higher resolution shots?Bear in mind we'd be looking through the clear gel, which doesn't have a flat surface. So high magnification images wouldn't be optimal.I'm going to be pretty busy this coming week. So, probably won't do this till sometime after the 26th.

author: electr_peter
author_rank: Unknown
timestamp: June 16, 2017, 10:16:08 pm
content: Grounding scheme looks interesting (on all 4 corner with 3-4 links and silicon goo).Is the board inserted into black connector and can be moved? If so, some diagnostic and repairs can be done by removing ground links. removing silicon (not sure how), unglueing the board (very likely that it is glued) and opening connector. Repair can be just possible for very desperate client by qualified repairmen.