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component identification & replacement: automotive diagnostic module

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M104-AMG

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Can someone help me in finding replacement components for a 16-year old automotive (Mazda) diagnostic module ?

Diodes:
Using my Fluke 79 DMM set to the "diode" mode, all of the circled diodes are testing "open" in both directions, which supposedly means ALL of these diodes are "open" and need to be replaced.

The only markings I see are a "D" or "O" and a "4" (see attached pics for details).

Transistors:
NEC J143
NEC B1151
K105

Thanks,
:) neil

BTW: input voltages are only 14.2-VDC, electrolytic caps are rated at 25-VDC, and have been replaced.
 

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Sceadwian

Banned
Do you know what those diodes do? It seems more than a little unusual that you'd lose 8 diodes like that. Have you tested the transistors to see if they need replacing or at least if they fail a diode test as well?
 
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pfofit

Active Member
What does this module do?

It looks to small for an ECM. Make,model year?
 

M104-AMG

New Member
The diagnostic module is an airbag diagnostic module and is used to "fire" the airbag.

I have no schematic, and it seems ALL of the same diodes test "open" in both directions.

Attached is a narrative of the function of the module.

The module gives me a "3-blink" error, which means there's something wrong in the power-supply to the diagnostic module.

The flow-chart says to test all voltage inputs into the module. If they pass, then there's something wrong with the powersupply INSIDE the diagnostic module.

From the transistor id numbers, this is high-current transistor (NEC J153).

I'm thinking the transistors wend bad, and then they took out the diodes.

I am de-soldering one of the NEC J153 transistors, as both are testing open, to test out of circuit.


What do you think ?

:) neil
 

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Nigel Goodwin

Super Moderator
Most Helpful Member
I seriously doubt all those diodes are bad, which makes me think they are all OK. Remove one and test it out of circuit, I bet it tests fine then (assuming your meter is OK).
 

M104-AMG

New Member
What does this module do?

It looks to small for an ECM. Make,model year?
Airbag diagnostic module, for a 1993 Mazda RX7.

Numbers on component:

NEC J143
21

I removed the transistors and both test "open" in the "diode" setting on my Fluke 79. Perhaps I'm testing it wrong.

How does "Gate, Drain, Source" map to "Emitter, Collector, Base" ?

Also, anyone have an equivalent part number from Digikey ?

:) neil

PS: now removing two diodes for out of circuit testing
 

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pfofit

Active Member
I am de-soldering one of the NEC J153 transistors, as both are testing open, to test out of circuit.

What do you think ?
I'm thinking that everything you test shows open. Are you sure the meter is good, your using it correctly :D or that the board isn't coated with something that's permitting contact with the leads.
 

M104-AMG

New Member
I'm thinking that everything you test shows open. Are you sure the meter is good, your using it correctly :D or that the board isn't coated with something that's permitting contact with the leads.
I double-checked how to use the "diode check" on the Fluke79, and I didn't put it in the right mode (hold down 2-seconds, not 1).

All silver-banded diodes test OK.

Two green-banded diodes failed. Their marking are"D4" or "4D". Any suggestions for these replacements ?

:) neil
 

M104-AMG

New Member
I am assuming the transistor marked NEC J143 is a 2SJ143 PNP transistor (see attached PDF).

Here's the map I used:

Gate = Emitter
Drain = Collector
Source = Base

Assuming the above, tests show both transistors bad.

Anyone know of an equivalent from DigiKey for 2SJ143 ?

Thanks,
:) neil
 

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pfofit

Active Member
The transistors indicated are mosfets and do not check like a regular transistor.

source to drain will read open until triggered by the gate at which point they will go short(a few ohms) depending on the gate voltage.
Two green-banded diodes failed.
In what way are they failed.

What is the resistance from resistance mode in both directions of the dud parts?
What are the readings in diode test both directions?
 
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M104-AMG

New Member
I lost one of the diodes.

Any idea on what replace them with ?

I could take one off the board, but there are no definitive identifying marks.

What measurements could I take and then make an educated guess ?

Thanks,
:-( neil
 
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