ECU's If they BLOW Are they BLOWN ?

Danny DeVito

Active Member
Joined
Nov 1, 2009
Messages
886
Location
Ireland
Car
V220 CDI
Example :- I cross jump leads and blow the bejaysus out of my ECU. Will it do anything ? Will it still do limp mode ? Will it be readable using diagnostics ?

If it's not answering to star will it do limp ?

If the Tech using STAR says 'ur ecu is blown !' will the car do safe mode ?

I am asking in general but related to Hanns Grubers faults
http://www.mbclub.co.uk/forums/engine/109534-esp-light.html
 

MarkJunedd

Active Member
Joined
Apr 10, 2010
Messages
361
Location
Swansea
Car
98 CLK320 Sport
Example :- I cross jump leads and blow the bejaysus out of my ECU. Will it do anything ? Will it still do limp mode ? Will it be readable using diagnostics ?

Not sure about the merc ones but the above is exactly what happened on my wifes old Fiat Bravo a few years ago. She came out of Uni and a chap on the same course had left his lights on all day and flattened his battery, "dont worry i've got just leads in the boot but you'd best connect them in case I get it wrong" says my wife. Next thing the numpty flashes the leads together after they are connected to my wifes car !!!! Result ? horrendous misfire and me having to replace the ecu. Made the sure the d**khead paid for it though. :mad:
 

grober

MB Master
Joined
Jun 22, 2003
Messages
29,975
Location
Perth, Scotland
Car
W204 ESTATE
Really depends on exactly the extent of the damage done. ---which depends on how well any protective circuitry has worked to screen any damage inducing voltages/spikes from the ECU. As for as I am aware "limp home mode " implies a fully functional ECU which is still capable to controlling /communicating with the engine /gearbox. It will go into LMM when it receives signals outwith expected values from various sensors in order to protect the car's primary systems. Its possible I guess that in some cases the input circuitry could be fried [ same result as erroneous sensor readings] while "the executive" and "output" stages continue to function. However if the "executive" part of the ECU is fired the unit will be dead. A fault on the ouput stage only would immediately give out of spec readings from the feedback sensors and would again probably mean LLM Really depends on the extent of the damage to the ECU. :dk:
 

BillyW124

MB Enthusiast
Joined
Oct 22, 2010
Messages
2,892
Location
North West London
Car
W124 E320 coupe, W211 E320 V6 CDI, W211 E63 V8 AMG, R129 SL 280 V6, W215 CL 600 V12 Bi Turbo.
Not sure about the merc ones but the above is exactly what happened on my wifes old Fiat Bravo a few years ago. She came out of Uni and a chap on the same course had left his lights on all day and flattened his battery, "dont worry i've got just leads in the boot but you'd best connect them in case I get it wrong" says my wife. Next thing the numpty flashes the leads together after they are connected to my wifes car !!!! Result ? horrendous misfire and me having to replace the ecu. Made the sure the d**khead paid for it though. :mad:


good point and good thread by Danny.

what is the deal surrounding Jump starting car's, especially new ones.

i heard with new motors jump starting is a massive NO NO
 

GP801

MB Enthusiast
SUPPORTER
Joined
Jun 18, 2010
Messages
3,087
Location
Sussex and Tuscany
Car
2003 W209 CLK, 2005 R171 SLK in UK, 1995 S124 E280 in Italy
good point and good thread by Danny.

what is the deal surrounding Jump starting car's, especially new ones.

i heard with new motors jump starting is a massive NO NO
It should be fine as long as you use a battery pack or the "donor" vehicle does not have the engine running. Also a good idea to use the specific jump start terminal under the bonnet rather than the battery itself if your car has one.
 

grober

MB Master
Joined
Jun 22, 2003
Messages
29,975
Location
Perth, Scotland
Car
W204 ESTATE
when all else fails consult the owners handbook. There are usually DETAILED instructions as to how to couple up the car to another power source. These must be followed to the letter as to the order and way the +/- leads are connected AND disconnected----- IGNORE AT YOUR PERIL :devil:
 

BillyW124

MB Enthusiast
Joined
Oct 22, 2010
Messages
2,892
Location
North West London
Car
W124 E320 coupe, W211 E320 V6 CDI, W211 E63 V8 AMG, R129 SL 280 V6, W215 CL 600 V12 Bi Turbo.
^ yes agree, gets overlooked
 

Dieselman

Banned
Joined
Jul 13, 2003
Messages
34,206
Car
Peugeot 403 Convertible
Not sure about the merc ones but the above is exactly what happened on my wifes old Fiat Bravo a few years ago. She came out of Uni and a chap on the same course had left his lights on all day and flattened his battery, "dont worry i've got just leads in the boot but you'd best connect them in case I get it wrong" says my wife. Next thing the numpty flashes the leads together after they are connected to my wifes car !!!! Result ? horrendous misfire and me having to replace the ecu. Made the sure the d**khead paid for it though. :mad:

Have you ever met a university student that wasn't completely thick when it comes to practical issues. :rolleyes:
 
OP
OP
Danny DeVito

Danny DeVito

Active Member
Joined
Nov 1, 2009
Messages
886
Location
Ireland
Car
V220 CDI
I studied electronics, a guy there was told my mates that the wires were different resistance depending on the colour of the insulation, they often had him remove all wires from his breadboard to correct non working projects.

And now following the point. How would you tell if and ecu was blown apart from smell or no response from it using star or whatever ?
 
OP
OP
Danny DeVito

Danny DeVito

Active Member
Joined
Nov 1, 2009
Messages
886
Location
Ireland
Car
V220 CDI
Great Sketch that one !

Normally for jumps i would

Connect leads to suitable locations usually under bonnet.

Start donor car and run for a short time mins usually

Then try start my car

Hows that ? I would not normally have a book to follow (as i do not for current car anyway )
 

neilrr

MB Enthusiast
Joined
Jul 20, 2004
Messages
6,790
Car
Various.
Wouldn't an OVP relay break the circuit & protect the ECU?
 

grober

MB Master
Joined
Jun 22, 2003
Messages
29,975
Location
Perth, Scotland
Car
W204 ESTATE
An OVP, if present, might protect against reverse polarity and high DC voltage. However it would have limited effectiveness against any RF/ AC induced currents/spikes from any spark arcs generated by poor contacts or large load/no load current surges.
 
OP
OP
Danny DeVito

Danny DeVito

Active Member
Joined
Nov 1, 2009
Messages
886
Location
Ireland
Car
V220 CDI

That says connect the earth with the donor engine running ! And with lights etc off. Isn't that contrary to previous discussion about blowing sam's etc ?

It also says to gently release the clutch when tow starting, i always was told to release and depress quickly.

No mention either of tow starting with dead battery ?

As for ovp, do the cars not already have some basic protection ?
 

Users who are viewing this thread

Top Bottom