Mikes1991

In the short period of time I have been a member here I have of course run into the Opti issue and I had a hard time tracking down what was really causing my no spark. I performed every test for a/c voltage signal to the ICM to continuity testing harness ECU everything. Ultimately it looks like it is my ECU and for good reason. here is a faq from a company that knows this ECU very well and rebuilds them in florida. My Ecu could not be in better hands. I have a 1993 40th ed and Im not sure but this may extend into the Pcms also. Read the faq below

This is what my problem was

Q. I heard that several GM computers that employ surface mount technology (SMT) may
become intermittent in operation over time due to manufacturing defects. Realizing
this, I replaced the ECM in my customers’ vehicle after performing a Tap-test to make
sure that the intermittent problem was in fact due to a defective ECM. However, the
vehicle still has an intermittent miss, even with the rebuilt ECM. Can this problem be
fixed?
A. This problem can be fixed, and it is fixed with every Blue Streak remanufactured GM
SMT computer. The reason that some SMT computers become intermittent is due to
the conformal-coat that is applied to the ECM circuit board. The conformal-coat is
applied to the circuit board to help protect the ECM from corrosion and the elements.
However, after some time, the conformal-coat may shift, swell, or spread, causing the
movement of certain electronic components on the board. This creates the potential
for intermittent contacts between these electronic components and the circuit board.
At Blue Streak, all remanufactured GM SMT ECMs have the original conformal-coat
removed, all solder joints are then re-flowed and the ECMs are exhaustively tested. A
new conformal-coat is then applied using a process that virtually eliminates the reoccurrence
of an intermittent ECM, and the ECM is tested once again. If after
installing the remanufactured ECM you still have an intermittent miss in the vehicle
and you have checked the wiring harness for chafing and shorts, chances are pretty
good that you have a problem with the vehicle wiring harness connector at the ECM.
If you remove the pins from the harness connector and cinch them down, they will
have a stronger grip on the ECM pins. This should eliminate your intermittent engine
miss.

My ECU is now in this companys hands and it is obvious they know what they are doing. The company is called blue streak and my parts rep is getting this whole job done for a lousy 127 dollars talk about cheap and thats shipped both ways. wow I got lucky on this deal and like I said knowing this now everything is suspect. I was getting the opti spark code and the problem isnt the opti but the ecu itself the very thing that is sending the code is the problem lol. Check your codes

onedef92

Outstanding tech support by the members here and your persistence (where a lesser man would have given up) is to be commended. Thanks so much for posting this, Mike. It's sure to help others down the road who find themselves in a similar situation.

toptechx6

Thanks for the update and ECU information. Reading this makes me feel pretty good, my 93 has a Blue Streak remanufactured ECM that was installed when I got the car and I was unsure of their reputation for quality. 92/93 ECM's seem to have some issues and many find it difficult to locate one when needed.
I even checked the Blue Streak web site but it did not look like they still offered the 92/93 ECM. Sounds like they will still rebuild them so perhaps it is a matter of core availability. They will be on my list if mine should fail, especially since their Florida location is about 10 minutes from home.

Mikes1991

Excellent yeah it seems like they really know there stuff vecause Im sure others just look for broken solders etc but these guys clean the entire board and reapply the seal thats a big difference and one Im sure others, especially small guys wont do or be able to do. From what I understand they are an affiliate of Borg Warner
With that being that you are 10 minutes away can you go down there and ask them hows my pouter doing. Obviously they are no overnight fix on this they take thier time and fix it right my parts man told me this. Im glad I called him first, would have never thought

Mikes1991

It really is and thank you for the compliment. You should have seen me play Hockey lol. Holy God talk about not giving up, I was beligerant to say the least. I guess that is where i learned some of this never give up mentality but again thank you for the compliment, It was very encouraging and yes this should prove helpful hopefully to others
Im gonna go and register my car today as I expect to be driving it very shortly please god. Talk to ya soon and thanks again

JAKE

Absolutely GREAT Information! Something I'd never come across before in all my reading and I sincerely Thank You for it.


In addition to the GREAT INFORMATION it also re-inforces the "Diagnose First; Repair Second" problem solving method.

Thanks again.

Jake

F22

Hey Mike, been following this all along. I know you'll come back after installing the ECU and tell us how it finally came out. Great job and hope that's the final step in getting your C4 (and you) back to being happy!

tblt44

So is that how you got this car,because the previous owner could not get it running???

Mikes1991

That is correct. I bought it and never even heard it run. I knew based on talking to him what was up and it was obvious he was broke and fed up with the car.

Mikes1991

Thanks jake
yeah Im surprised this isn't known. Looks like my research methodology skills learned in college have served me well lol

ragni

This is good to hear for my DTC 36 problem. I'm not about to commit to an Opti swap until I'm sure it's the Opti!

What code was yours throwing?

And in general and at the expense of sounding like a complete idiot; on a 94 LT-1 are the ECM & the PCM separate units or are these names interchanged to refer to the same unit mounted over the hydraulic clutch master cylinder and reservoir on the drive's side near the fire wall?

If they are separate units, where is the ECM located?

toptechx6

Through model year 1993 the engine computer was termed ECM, or Engine Control Module, automatic transmission shifts were controlled by a hydraulic governor. In 1994 automatic transmission shifts became electronically controlled and the software for that function was incorporated in the module located at the rear of the engine compartment on the left side as you indicated. At that time the terminology changed to PCM or Powertrain Control Module.

ragni

So, for my 94 LT-1 with 6 speed manual there is the PCM only. No additional ECM.

Correct?

toptechx6

Correct, the terminology is the same regardless of transmission beginning in 1994.

ragni

Phew. Thank you. I was going nuts trying to figure that out.

Mikes1991

Yeah the 1994 above was termed a PCM because of the control of the automatic from the computer as opposed to the tv cable

choopes

I have had a long term suspicion that it was something else, besides the opti at fault with my '93. This is indeed good information. Please keep us posted as to how you progress, also how hard is the unit to change?

rcr29kh

Now you have me wondering--I really think I have seen both terms used in the 94 FSM which was a bit confusing--thanks for clearing this up!

ragni

Right. That's partly what caused my confusion. Don't ask me to go back and cite where, but I know I saw reference to an ECM in my 94 FSM. As though they didn't update the verbiage in the FSM to match the updated hardware from 93 to 94.

rcr29kh

I want to say it was in the FSM troubleshooting diagrams that I saw it. I was trying to troubleshoot a stall no restart hot condition that ended up being the Opti. It's almost like the FSM uses it interchangeably--PCM one place and ECM another