Quick summary:
- less than 14,000 orig miles
2008 - installed a Cardone serviced ECM
2012 - installed MSD Ignition Pro-Billet LT1 Distributors 8381 "Opti-Spark"

- In 2008, the car would randomly shut off while driving and occasionally show some lights on the panel. The Cardone ECM solved the problem.

- In 2012, the car would again just shut down, and installing the new Opti-Spark system solved the problem.

- The problem has returned. Car shuts down while driving, typically after 15-25 minutes of driving.

Since I went "high-end" with the MSD Opti-Spark, I am thinking that the ECM is the problem again. It does NOT throw any codes, just "1-2".

I opened the ECM to see what Cardone replaced, working on the assumption that most of these boards have a consistent failure point. Cardone replaced only one component -- a transistor (possibly triac?) Q7. Does anyone have a schematic or parts list for this ECM that would be able to identify a modern replacement part number for Q7? It reads "9707, then a diode symbol, then R9523" I cannot find any useful info from a Google search. Q6 is apparently a similar part, and can be seen quite clearly in the photos. Q6 reads "9707, diode symbol, R9225". I could not find any info about Q6, either.













Additionally, if you have any additional thoughts on this overall problem (shutting down), that is appreciated.
Thanks.

 

You didn't mention a year or the part number of the ECM.

It looks like Q7 got very hot and crystalized the solder. Resoldering it might fix your problem (assuming the cause of the overheating is now gone).

I - diode symbol - R is the brand symbol for International Rectifier. They made a lot of the driver transistors for the fuel injectors, which appear to be what you're looking at. Considering how old these cars are, the possibility that this part is still available is mighty slim. IR does make modern versions of these parts, but you have to buy at least 100 at a time.

Ludis Langens had a lot of ECM schematics on his web site. The site is gone, but it has been mirrored here:

http://www.exatorq.com/ludis_obd1/

 

Those are the output drivers for the injectors- probably mosfets. might be in parallel...one goes and drops down the entire rail although for the LT1, the injection is sequential, but they do share 12v.

 

I would ohm the injectors to, because a bad coil could be causing the driver to overheat.

 

Thanks to both of you (Cliff Harris and mike100) for the feedback. You are both right as far as I can tell. I should have recognized the IR brand, so good catch there.

(FYI - 1993 Corvette anniversary model).

I think mike100 is right that Q6 and Q7 may be in parallel based upon probing them with a meter. I can't find a schematic for 1993 ECM on that site you linked.

These Q7 solder joints are just typical quickie-by-hand solder joints from when the last cardone tech replaced this part. I think to make any lasting progress, I will need to replace both Q6 and Q7.

If anyone else knows of a source for new replacements for Q6 and Q7, that could be useful to a lot of guys here trying to fix ECM problems.

 

Good advice, I will do that, too.

I think that I may have made some progress with the component searches, as soon as I verify the info, I will post it.

 

I was an electronic engineer until I retired and received a lot of information from manufacturers over the years. The link I had no longer works, but I did find this:

http://www.irf.com/application-solut...njclw#tab-tab1
http://www.irf.com/application-solut...njclw#tab-tab3

The problem I see there is that our MOSFETs are TO-220 package but they don't show any.

I did look into buying some of these parts last year. I couldn't find stock on any of them. That means that you have a to order a huge quantity so they can justify going into production to make them. Obviously the ECM rebuilders get their parts from somewhere, so the parts are out there. It's possible the rebuilders are not using the best parts. The main criterion is low rds(on), which means the resistance from drain to source when the transistor is turned on. The lower it is the cooler the transistor operates.

 

I contacted International Rectifier, and they said that the part number is 9707 (top line of each part). They also said that these were custom for the OEM (GM), and that Gm must be contacted regarding availability.

Re - Cliff Harris... IR does make a TO-220AB power mosfet with easily availability (less than $2 ea at Mouser). See-
http://www.irf.com/product-info/data...rf9z24npbf.pdf

I asked about this irf9z24n, but the I-R tech would not make any comment whether it would be a replacement for the 9707.

If you have an opinion about this irf9z24n as replacement, let us know. Thanks. In the meantime, I am still contacting sources to see if I can locate any 9707.

 

Also, at this I-R page, you can find the auto mosfets, and can narrow the search to TO-220 / TO-220AB using the 2nd column header:
http://www.irf.com/product/Automotiv...nje2d#tab-tab1

 

That circuit is lifted. ECM is done. This happened to me on a 93 about a year ago.

 

I don't know what you mean, but I do electronic repair, and nothing about the circuit indicates any reason why it could not be repaired with new mosfets.

 

Look at your second picture. The circuit is completely lifted that is why it is wrinkled. The entire circuit has gotten hot. I have never seen an ECM come back from that. The start circuit on a battery charger, the 200 amp setting is what can cause that right there.

 

virtually any circuit board can be repaired, use wire jumpers to replace the burned traces

 

What I would do in the case of a lifted pad is insert the transistor and fold the lead over and align it with the trace and then solder.

I have fixed a lot of PC boards with lifted traces and it is definitely possible and not too hard to replace a trace with a piece of solid wire.

One thing to watch out for that I have seen is to glue the trace to the PC board with cyanoacrylate (crazy) glue. When you solder to it you get cyanide gas -- that'll burn your nostrils.

 

9707 is a date code. July 1997.

 

I did find the original information I was looking for:

http://www.irf.com/press-room/press-releases/nr100331

The links that rpesq posted seem to be later versions of IR's automotive MOSFET lineup.

 

Hey I hate to bother you but I'm trying to find pictures of the circuit boards in a 1984 ECM #1226026 can you please give me a litte advice as to wich direction to go