Hey Gang,

Here's a new one for me... I have a '98 coupe. Have never had any real electrical problems before, and I suspect this is probably a connection problem (water intrustion or corrosion on a connection(s) somewhere), but hopefully someone will know for sure.

I drive the car almost daily, and when I headed out a few days ago, I got a few miles and all of a sudden the DIC lit up and said 'reduced engine power', and then 'check traction system', and the check engine light came on. It immediately had no power was running rough and if you pushed on the throttle nothing would happen. I pulled over, shut the car off, waited a minute, restarted, and it started the same way. Shut off, waited maybe 3 minutes and restarted, and ran fine. Drove home and checked the codes and this is what I got:

PCM: P1125 and P1276
TCS: C1278

I had to go out of town, and just tried to start it again yesterday, when it started, it immediately did the 'reduced engine'-traction system scroll on the DIC again, and was running the same as it did the last time this came up. Shut it off, checked codes and got this:

PCM: P1515
TCS: C1278
BO-RFA: U1096 and U1064

Cleared the codes and it has ran fine the 4-5 times I started and drove it yesterday. And I just started it and let it run for about 5 mins and the same.

Any and all help is much appreciated.

Thanks!
Ken

 

Could be the TAC module that is connected to the Computer itself... I had this happen to my 97 several times both of which were on the highway at speed trying to pass...talk about pucker factor! I asked the same questions and was told the early models had issues with the TAC module...I since replaced it and have had no more issues...

I don't think I had any codes though with mine....when I checked then they all were (H) or history...

Hope this helps - I am sure more will chime in on this issue...

-Note the TAC module is located on the cars computer, jack up pull passenger front tire and remove the inner fender well cover (you will see the bolts) the TAC is actually bolted to the computer itself) very easy to do..if this is in fact the issue...

 

ttt

 

Seems like I saw a thread here that said you may need to find and clean all the grounds. IE where the electrical system is grounded to the chassis. Here check this out!
http://forums.corvetteforum.com/showthread.php?t=896875

 

Look for bad grounds, water-damaged connectors at the TAC module, and possibly a chafed wire harness at the rear of the left cylinder bank, as it passes around the bracket that's back there. I too had the same problem, and after two trips to the dealer with no results, I dug into it myself. Pulled the battery, inspected for the dreaded acid leakage, but found no evidence. Opened up the passenger side wheelhouse access to the TAC and PCM modules, and found a severely pinched and nicked ground wire. Spliced in a new piece, reconnected to the ground stud under the battery, and problem hasn't happened for over 4 months now. It was so bad prior to doing this that it was happening almost every time I drove it.

 

Thanks!

 

It is a FACT that the 97 and most 98 C5 had Throttle Actuation Control (TAC) module that were defective. My 98 coupe had the exact same issue. Mine was also complicated by bad grounds. It got so bad that i wanted to burn the sucker!!! I couldn't trust driving the car any great distance from home. It would just DIE.

I found that if the Reduced power syndrone was bad enough and I couldn't get it to run normally, I could clear all of the DTC codes and get it to recover quicker.

I changed out the TAC module and cleaned the grounds and it has been trouble free for 5 years now.

The TAC module is in the passengers fender and is mounted outboard the PCM. It is a plug and play module. You can get it at a discount from Fred Bean Chevy or fitchners Chevy mail order (both are forum sponsors).

I can't stress cleaning the grounds enough. If they are corroded or in poor condition, you will have nothing but headaches as long as they are bad.

I have a very good post on that very topic.

BC

 

110% in fact - it was Bill above who helped me with mine and my turn signals on crack! Mine is a 97 and the grounds for the signals were terrible!...

Bought the TAC from Fred Beans for $140 I think...

 

I had the same thing on my 99, turned out to be a loose ground. THe one under the battery. Do a search on grounds , and you will see where there at. Good luck, Jim.

 

 

Could a faulty, bad connection, etc. involving the TAC, give you a P0300, misfire code?

 

NO! You need to check the plug wires first. Carefully remove them by twisting the boots and then pulling on the boots to remove them from the plug. See if they are torn, corroded inside the boots or melted. Then use an ohm meter and read each wire end to end. They should read 250 - 750 ohms. If they are a lot more than that they are toast!

If the wires are good, check the plugs.

If the plugs and wires are good, check for a broken valve spring or a bent push rod.

Bill C

 

Thanks Bill, I have new plugs and wires, ready for install tomorrow, I have already removed the old plugs and wires and they do look OK to me.

 

Put on new AC Delco Iridium plugs and GM Performance Plus wires, went for 2 short rides, runs good, and no codes so far. Can a slight cut on the outside of 1 wire make the car run that bad.

Thanks for the help,

Charlie

 

Put the bad wire back on and start the car, Grab the cut area with one hand and the block with the other. If there is a leak, you will know in very short order!!!

On a more serious note, yes! If it is deep enough to allow the High Voltage to leak out. Check the resistance of the wires. That is usualy the issue with them.

BC

 

Thanks for the offer Bill, but I think I'll pass. I'm not sure you can even call it a cut, more like a scuff with a little nick in it. I'll check with a meter tomorrow at work just to see for sure. Hard to believe how bad the car was running. So far So good!! Thanks again.