Caterpillar ECU repair, need N548AB replacement?

[eccerr0r]

Re: Catapillar ECU repair, need N548AB replacement?

Other end of the wire should still be continuous with some pad somewhere...at least one would hope they would design the tracks to not fuse before silicon or die bond...

[Agent24]

Re: Catapillar ECU repair, need N548AB replacement?

Nope. No fuel, as there isn't any HV produced. There is no short to the gate on both, so the gate driving circuit is fine.

Hopefully not the case here if both are measuring the same, but I've seen MOSFETs that blew hard enough that they went open circuit after the event, while acting as a fuse for the now dead-shorted gate drive.

[eccerr0r]

Re: Catapillar ECU repair, need N548AB replacement?

%#*$!@ those multilayer boards...

[CapLeaker]

Re: Catapillar ECU repair, need N548AB replacement?

The 3 pin caps measure about 1400uF on my tester. There are no ratings printed on these caps. It also seems these 3 legged caps aren’t connected to these TO247 devices. 2 of the pins of the TO247 go to the connector while the 3rd pin is just floating. Which doesn’t make any sense. It looks like it goes to a pad and a through hole that doesn’t come out on the other side. I’ve actually made a copper brush to my DMM to find a pad where it comes out but can’t find anything on either side of the board. While pin 2 and 3 of the two TO247 devices are in parallel, pin 1 is separate which I believe is the gate pin. Sine it isn’t connected anywhere it must be floating. Even my dog thinks I ate her kibbles. I’ve made a pic from the other side of the board. That’s where I left for tonight. Maybe I’ll have another go at it tomorrow…
I know the ECU is from a Catapillar MXS maybe a C15

[eccerr0r]

Re: Catapillar ECU repair, need N548AB replacement?

are source or drain grounded? Drain or source connected out to the pins?
Found which pin is ground? battery 24V? 12V?
Those three pin axial devices are capacitors? What voltage/capacitance?

[CapLeaker]

Re: Catapillar ECU repair, need N548AB replacement?

redwire:
Interesting indeed. I already had guessed the voltage should at 100V - 200V (from a different ECU) so that is inline with your buddies thinking. The 2 big, 3 legged blue caps are wired in series to each other. The drain and source pins of the fet are in parallel connected and go to the plug that solders into the main board.
Get this: The 2 gates are NOT parallel between the two fets and they do not go to that plug that solders to the main board either. So far I have not been able to figure out where the gates go. I measured gate to gate and nothing at all. Its again a multi layer board and can't see through it at all. Maybe I'll doodle up a picture later on and post that.
Matter effect I can't see any gate drive circuit on that power board. So I had ass/u/me/ed at one point that the gate drive maybe on the main board. Well that is not the case.
I must sound like I got mad cow disease or had my dogs kibbles for breakfast, lunch and supper?! Can it be that the gate has been just left floating? Oooff!

[peterzilla]

Re: Catapillar ECU repair, need N548AB replacement?

I was surprised to see that too.

[eccerr0r]

Re: Catapillar ECU repair, need N548AB replacement?

So this is BS, catapillar trucks have a lifetime of 10 or years max because the battery is not a FRU - and one must get a new ECU every 10 years?

[redwire]

Re: Catapillar ECU repair, need N548AB replacement?

Asked my friend who designs ECU's and this is what he mentioned:
You'll need to ID what the mosfets are driving and if they seem to be N-ch (low-side) or P-ch (high-side). If they are driving the "electronic unit injectors", it's a guess as to their voltage rating.
For a diesel engine, it's like a gasoline fuel injector - the amount (pulse-width) of the squirt is your fuel amount, but a diesel faces much more pressure and the timing of the squirt is your ignition timing, so you need speedy operation.
So it is common to hit the solenoid very hard with 50-200VDC pulse at 20A and then less drive PWM down to say 12VDC for hold. So it is a peak and hold drive. It can be a single "master output" that gets switched to each cylinder by smaller mosfets, that select which cylinder. There is no overlap between cylinders so one power switch can do all the hard work.
The ECU should have a boost-converter for this, what is the HV electrolytic cap rated at? It would give some idea of the mosfet's voltage. Not the 1,300uF 35V part but the other big blue one.

The lithium battery is likely for a real-time clock, this is for time-stamping trouble codes and also for time-stamping driver's habits. There can be GPS on the truck available through the SAE J1850 bus which would set the clock, or use a scantool. I guess you can track the driver's foot stomping with geolocation and time/date in some trucks.

The thermal adhesive is usuallty two-part, Henkel or Dow and glue for the enclosure is typically Dow 7091.

[CapLeaker]

Re: Catapillar ECU repair, need N548AB replacement?

Had no active immobalizer or related codes.

[stj]

Re: Catapillar ECU repair, need N548AB replacement?

i meant in the ecu!

some fuckers - i know john deer is one, need fault codes cleared with a service tool or they wont run.

[CapLeaker]

Re: Catapillar ECU repair, need N548AB replacement?

Nope. 18 wheeler works fine on a other ECU.

[stj]

Re: Catapillar ECU repair, need N548AB replacement?

imobiliser active / service scam activated?

[CapLeaker]

Re: Catapillar ECU repair, need N548AB replacement?

Nope. No fuel, as there isn’t any HV produced. There is no short to the gate on both, so the gate driving circuit is fine.

[sam_sam_sam]

Re: Catapillar ECU repair, need N548AB replacement?

Unless it took out the device that supplies power to the mosfets but yes you would think might be the case

[eccerr0r]

Re: Catapillar ECU repair, need N548AB replacement?

shorted drain - source

Wouldn't that mean stuck on and fuel keeps going?

[CapLeaker]

Re: Catapillar ECU repair, need N548AB replacement?

Great job desoldering all that, that's a lot of work

I would beep out the ECU connector pins to see what they end up connecting to. Because of the big TO-247 package and heatsinking, wild guess is the fuel rack solenoid, as a high current load.
I'll check with someone in the business, but there might be a HV DC-DC converter sometimes to make say 100VDC for driving big solenoid loads and the mosfets might be for that. I'd think they get power from the big caps, not from 24VDC.

That is what I was thinking. The truck doesn't start, because it didn't get any fuel, because the solenoids not firing. The truck would run on ether, but then die. The TO247 mosfets are in parallel, both are shorted drain - source. I also think that these mosfets should be a HV range and not get 24v.

[petehall347]

Re: Catapillar ECU repair, need N548AB replacement?

No Sir! I tried my darnedest to find a spec sheet on that N548AB and found diddly squat! There are not even any markings on these 3 legged caps. But I did figure out that this ECU came out of a 2007 Catapillar MXS engine.

wondering what it is

[eccerr0r]

Re: Catapillar ECU repair, need N548AB replacement?

If it really is a suicide battery, I wonder what got lost...

[redwire]

Re: Catapillar ECU repair, need N548AB replacement?

Great job desoldering all that, that's a lot of work

I would beep out the ECU connector pins to see what they end up connecting to. Because of the big TO-247 package and heatsinking, wild guess is the fuel rack solenoid, as a high current load.
I'll check with someone in the business, but there might be a HV DC-DC converter sometimes to make say 100VDC for driving big solenoid loads and the mosfets might be for that. I'd think they get power from the big caps, not from 24VDC.