popshumphrey

I have written many posts about my TAC and the reduced engine power. I replaced the TAC with one from vettenuts. What I have found out is that I did not specify that I wanted a TAC post 99 and therefore have a pre99 TAC that was sent. Note: I did not specify! However, the car is running great. Marc is willing to exchange it with a 00-03, but the mistake was mine and the car is running just fine. Would you change it to the post 99 or just drive the pre99. Again, it seems to be doing fine.

Marc at Vettenuts said he did not know of any problems unless you went to very high horsepower.

Any response and help would help me decide. Vettenuts have been great to respond and work with me.


thanks folks! Pops....

popshumphrey

anybody got an opinion?

tblu92

Can you explain exactly what code you are getting ?? TAC is a vague description what exactly do you mean ?

popshumphrey

I was getting reduced engine power. Problem has gone on for a month or so when I replaced the Throttle Accuator Control [TAC]. It is the computer box in the passenger fender well. It has been known to cause problems. So I replaced it with a 97/98 TAC which are known to have problems. The question becomes whether I should replace it with an 00-03 model.

Pounder

If Marc is willing to trade and you don't mind replacing it and you just want your own piece of mind than do it !!!!!

CactusCat

I just looked up replacement TAC for C5 Corvette and the same part # is listed for 1997-2004, so if that's the case, I don't think changing would help. However, I have read in the past that there were some issues with the 97-98 TACs (Bill Curlee's words) but do some homework and see if your currently installed TAC has the same part # as the newer 99-04 TACs. If they're the same, I wouldn't worry about it.

popshumphrey

CactusCat you are right. Where can I look up the part number when I pull it off the TAC. I can search so this becomes a I am lazy question. What web site would show the 99-04 part number

CactusCat

I found the part in this thread. https://www.corvetteforum.com/forums...-pictures.html You'll have to scroll down a ways, but the ACDelco / GM part # shown is 19245405. I then did a Google search for GM Part# 19245405 to see the cost and they all show for 1997-2004. Hope this helps.

LoneStarFRC

No such thing as "pre/post '99", or any other year. All the same.
19245405 AC Delco reman units readily available.

popshumphrey

Where would you get a remanufactured unit? Could not readily find one. Just curious Lonestar!

LoneStarFRC

https://www.google.com/url?sa=t&rct=...zJz2d3VK4zci7A
https://www.google.com/url?sa=t&rct=...W1NaXpmx5AsK6g

Rock Auto also lists it but seems to be out at the moment. They also show up used on Ebay from time to time. I'd bet Marc has some good used ones @ Vettenuts.net. EFI Connection used to have some reman units in stock (I bought one from them before) but not sure if they still carry them or have any right now. Haven't checked in a good while.

HTH

psiconversion.com has some ACD reman units as well. They keep them for guys doing LSx retrofit into cars/trucks/streetrods, etc. The Cadillac CTS used that same module for a couple years also.

http://www.ebay.com/itm/GEN-III-CORV...-/180862034883

LoneStarFRC

These things are actually pretty robust and are not high failure-rate items overall.

Having experienced REP issues in the past, one thing I WILL say though is that the connector plugs (mainly at the pcm end of things where it's exposed to the elements more so like moisture, dust/dirt, etc) HAVE to be free from any contaminants of ANY sort. Moisture/corrosion/dirt and/or just general detritus WILL cause issues. When connecting/disconnecting pay special attention to cleanliness of the connectors and their pins, etc. Compressed air and/or some spray contact cleaner can be your friend.

Bill Curlee

In Bill Curlee's words!

Heres the GM TSB:

Document ID# 410906
1997 Chevrolet Corvette


--------------------------------------------------------------------------------


Subject: REDUCED ENG. POW. MESSAGE ALONG W/ PARTIC. PWRTRAIN, DTCs P1516, P1518 and/or P1125 #87-65-16 - (03/24/1998)


SUBJECT: REDUCED ENGINE POWER MESSAGE ALONG WITH PARTICULAR POWERTRAIN TROUBLE CODES (INSTALL NEW TAC-MODULE IF STRATEGY IN SERVICE MANUAL FAILS)

MODELS: 1997-98 CHEVROLET CORVETTE WITH 5.7L V8 ENGINE (VIN G - RPO LS1)

CONDITION #1: INTERMITTENT REDUCED ENGINE POWER EVENT, ACCOMPANIED BY P-1516, OR P1518 TROUBLE CODES.

IF A SITUATION ARISES WHERE A P-1516 TROUBLE CODE IS ACCOMPANIED BY A

P-1120 AND/OR P-1220 TROUBLE CODE, THIS SERVICE BULLETIN DOES NOT ----------------------------------------------------------------- APPLY. IN THESE CASES THE TECHNICIAN MUST USE THE NORMAL STRATEGY ------------------------------------------------------------------ BASED DIAGNOSTIC. -----------------

CONDITION #2: INTERMITTENT REDUCED ENGINE POWER ACCOMPANIED BY TROUBLE CODE P-1125 AND ANY OF THE FOLLOWING TROUBLE CODES:

P-1276 P-1281 P-1286

CAUSE:

CONDITION MAY BE DUE TO DIAGNOSTIC SOFTWARE AND CALIBRATION IN THE TAC-MODULE WERE NOT OPTIMALLY UTILIZED.

CORRECTION:

IF THE ABOVE CONDITIONS CANNOT BE CORRECTED USING THE NORMAL STRATEGY BASED DIAGNOSTICS LISTED IN THE SERVICE MANUAL, INSTALL THE NEW TAC- MODULE LISTED BELOW.

PART INFORMATION:

NEW TAC-MODULE PART # 25319443

PARTS ARE EXPECTED TO BE AVAILABLE ON APRIL 6, 1998 FROM GMSPO.

WARRANTY INFORMATION:

FOR VEHICLES REPAIRED UNDER WARRANTY, USE:

LABOR OPERATION: J-5582 LABOR TIME: 0.5 HR

FIGURES: 00 ATTACHMENTS: 00

GENERAL MOTORS BULLETINS ARE INTENDED FOR USE BY PROFESSIONAL TECHNICIANS, NOT A "DO-IT-YOURSELFER". THEY ARE WRITTEN TO INFORM THOSE TECHNICIANS OF CONDITIONS THAT MAY OCCUR ON SOME VEHICLES, OR TO PROVIDE INFORMATION THAT COULD ASSIST IN THE PROPER SERVICE OF A VEHICLE. PROPERLY TRAINED TECHNICIANS HAVE THE EQUIPMENT, TOOLS, SAFETY INSTRUCTIONS AND KNOW-HOW TO DO A JOB PROPERLY AND SAFELY. IF A CONDITION IS DESCRIBED, DO NOT ASSUME THAT THE BULLETIN APPLIES TO YOUR VEHICLE, OR THAT YOUR VEHICLE WILL HAVE THAT CONDITION. SEE A GENERAL MOTORS DEALER SERVICING YOUR BRAND OF GENERAL MOTORS VEHICLE FOR INFORMATION ON WHETHER YOUR VEHICLE MAY BENEFIT FROM THE INFORMATION.

COPYRIGHT 1998. GENERAL MOTORS CORPORATION. ALL RIGHTS RESERVED.



--------------------------------------------------------------------------------

I believe that the CHANGE OVER part number happened somewhere early 1999.. My 98 had the same issue and the 99 part was supplied:

NEW TAC-MODULE PART # 25319443

Bill Curlee

As far as I know. (that's not vary far) ALL TAC modules for LS1- LS6 will function the same. The early TAC modules (97-98) were LESS RELIABLE than the later modules.

The TSB provides a replacement part# NEW TAC-MODULE PART # 25319443 and there may be other numbers as the years progressed. I SUCK on keeping track of what part numbers replace other numbers..

POPs... If it were me,,, I would look into getting a later TAC module.

Bill

LoneStarFRC

If indeed the 97-98s were having more issues, I agree with the idea of getting an ACD reman unit if needed, since I'm confident they are most likely to have any improved circuitry or circuit changes that were made back in the day.
After checking my records, it turns out the ACD reman unit I bought a couple years ago was from PSI Conversions, not EFI Connection. The PSIC in-house part number they assign to it is ACC-1010. It does come with the AC Delco label and part number though.

https://www.psiconversion.com/produc...ct-description

HTH

popshumphrey

The part number of the 97 TAC that I removed is 25312786. The part I was sent was 25311783. Marc at vettenuts, a great guy, is parting out a 2000 and is sending me that TAC. He also said the APP can sometimes cause this problem as well. After I replace the TAC again with a 2000, that we know is a 2000, I will drive and then if it acts up replace the APP. Thanks for all the help and that is my current direction.

The car kicked up the reduced engine power yesterday and then went away. It is acting exactly like the GM memo describes. Thanks Bill.

Blessings, Pops.

popshumphrey

Folks, I have now put in a 2000 model TAC. However, the codes did kick up last night. Could it be the APP or the TPS? I am at least moving along, ever so slowly. Pops.....

Bill Curlee

Pops What specific DTC/s are you seeing?????????

Bill

popshumphrey

P1125, P1281, and subsequent c1278