Are TAC modules the same for all C5s???
Melting Slicks
Joined: Apr 2002
Posts: 2,631
Likes: 2
From: Clever, MO aka SOMO
I got one 4 yrs ago from Bob Wendorff, the parts mgr, at Fichtner Chev for about $200. I've used them several times for my '98 parts. They are one of our CF sponsors. Check with Gene Culley at GM Parts also.........another sponsor.
Thread Starter
Safety Car
Joined: Feb 1999
Posts: 4,043
Likes: 342
From: Central NJ
Thanks for the info. I am just guessing that the TAC module is bad so I am looking for one, perhaps used, but working, that I can buy cheaper. What I really needed to know was are they all the sdame for all years. I guess I can can the vendorsa and ask..Thanks
Tech Contributor
Joined: Dec 1999
Posts: 32,910
Likes: 2,402
From: Anthony TX
CI 6,7,8,9,11 Vet
St. Jude Donor '08
They are the same for all years BUT,,,,,the early TAC modules had problems and GM up-graded them in 99 You need a TAC for a 99+ C5. Gene Culley had the best prices now. I got mine from Ficthners Chevy back in 2000.
If you get reduced engine power for no reason, the TAC module could be at fault. If you get reduced power, you can enter the DTC routine and clear the PCM codes and you should be back on the road temporally
BC
Thread Starter
Safety Car
Joined: Feb 1999
Posts: 4,043
Likes: 342
From: Central NJ
They are the same for all years BUT,,,,,the early TAC modules had problems and GM up-graded them in 99 You need a TAC for a 99+ C5. Gene Culley had the best prices now. I got mine from Ficthners Chevy back in 2000.
If you get reduced engine power for no reason, the TAC module could be at fault. If you get reduced power, you can enter the DTC routine and clear the PCM codes and you should be back on the road temporally
BC
If you get reduced engine power for no reason, the TAC module could be at fault. If you get reduced power, you can enter the DTC routine and clear the PCM codes and you should be back on the road temporally
BC
Is it possible for the TAC module to be bad and not get codes? Here is the deal. It a 98 heads\cam car with 3.73s and high stall converter. It runs fine when just driving around town. When you go WOT its almost like the car just shuts down. Kinda likes it hitting the rev limiter, but is actually nowhere near redline. There is about 9 degrees of KR at WOT at some points. The car is professionally tuned, the PCM was replaced, all grounds were checked and seem to be fine and like I said no codes. The fuel injectors were also tested and were perfect. The tranny was rebuilt and that was fine as well. It certainly seems electrical to me. So I was thinking it could need a crank sensor relearn, but what I undertand there is no option for that on a 98. The next think on my mind was the TAC module and or TPS. Do you have any suggestions for me.....Thanks a lot.... Tony
Tech Contributor
Joined: Dec 1999
Posts: 32,910
Likes: 2,402
From: Anthony TX
CI 6,7,8,9,11 Vet
St. Jude Donor '08
A failed TAC will set a DTC and or cause he car to go into limp home mode "reduced engine power" . It can also cause cruise control issues just for you knowledge. Nine degrees of KR is a lot and you need to figure out whats causing that. You need to make sure that the fuel pump is keeping pace with engine demand, Have you ever conducted an engine recarbonization procedure? You might need to.
Do you have any DTCs showing??
Bill
Do you have any DTCs showing??
Bill
Bill,
Is it possible for the TAC module to be bad and not get codes? Here is the deal. It a 98 heads\cam car with 3.73s and high stall converter. It runs fine when just driving around town. When you go WOT its almost like the car just shuts down. Kinda likes it hitting the rev limiter, but is actually nowhere near redline. There is about 9 degrees of KR at WOT at some points. The car is professionally tuned, the PCM was replaced, all grounds were checked and seem to be fine and like I said no codes. The fuel injectors were also tested and were perfect. The tranny was rebuilt and that was fine as well. It certainly seems electrical to me. So I was thinking it could need a crank sensor relearn, but what I undertand there is no option for that on a 98. The next think on my mind was the TAC module and or TPS. Do you have any suggestions for me.....Thanks a lot.... Tony
Is it possible for the TAC module to be bad and not get codes? Here is the deal. It a 98 heads\cam car with 3.73s and high stall converter. It runs fine when just driving around town. When you go WOT its almost like the car just shuts down. Kinda likes it hitting the rev limiter, but is actually nowhere near redline. There is about 9 degrees of KR at WOT at some points. The car is professionally tuned, the PCM was replaced, all grounds were checked and seem to be fine and like I said no codes. The fuel injectors were also tested and were perfect. The tranny was rebuilt and that was fine as well. It certainly seems electrical to me. So I was thinking it could need a crank sensor relearn, but what I undertand there is no option for that on a 98. The next think on my mind was the TAC module and or TPS. Do you have any suggestions for me.....Thanks a lot.... Tony
Thread Starter
Safety Car
Joined: Feb 1999
Posts: 4,043
Likes: 342
From: Central NJ
A failed TAC will set a DTC and or cause he car to go into limp home mode "reduced engine power" . It can also cause cruise control issues just for you knowledge. Nine degrees of KR is a lot and you need to figure out whats causing that. You need to make sure that the fuel pump is keeping pace with engine demand, Have you ever conducted an engine recarbonization procedure? You might need to.
Do you have any DTCs showing??
Bill
Do you have any DTCs showing??
Bill
Drifting
Joined: Dec 2005
Posts: 1,720
Likes: 3
From: East Hampton CT
Whats your DIC reading for battery voltage at high rpm when that problem happens? On older cars (non-C5's) I have seen weak alternators have issues at high rpm and cause sputtering and other issues like you describe. If one of the diodes in the voltage regulator is bad, you'll even get some AC current which the ECU does NOT like. Checking FREE things first is always the best way to start troubleshooting, and often solves the issue!
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Thread Starter
Safety Car
Joined: Feb 1999
Posts: 4,043
Likes: 342
From: Central NJ
Whats your DIC reading for battery voltage at high rpm when that problem happens? On older cars (non-C5's) I have seen weak alternators have issues at high rpm and cause sputtering and other issues like you describe. If one of the diodes in the voltage regulator is bad, you'll even get some AC current which the ECU does NOT like. Checking FREE things first is always the best way to start troubleshooting, and often solves the issue!
No idea what the voltage was reading.....I can see keep an eye on that...Thanks
1st Gear
Joined: Jun 2008
Posts: 1
Likes: 0
Bill,
Is it possible for the TAC module to be bad and not get codes? Here is the deal. It a 98 heads\cam car with 3.73s and high stall converter. It runs fine when just driving around town. When you go WOT its almost like the car just shuts down. Kinda likes it hitting the rev limiter, but is actually nowhere near redline. There is about 9 degrees of KR at WOT at some points. The car is professionally tuned, the PCM was replaced, all grounds were checked and seem to be fine and like I said no codes. The fuel injectors were also tested and were perfect. The tranny was rebuilt and that was fine as well. It certainly seems electrical to me. So I was thinking it could need a crank sensor relearn, but what I undertand there is no option for that on a 98. The next think on my mind was the TAC module and or TPS. Do you have any suggestions for me.....Thanks a lot.... Tony
Is it possible for the TAC module to be bad and not get codes? Here is the deal. It a 98 heads\cam car with 3.73s and high stall converter. It runs fine when just driving around town. When you go WOT its almost like the car just shuts down. Kinda likes it hitting the rev limiter, but is actually nowhere near redline. There is about 9 degrees of KR at WOT at some points. The car is professionally tuned, the PCM was replaced, all grounds were checked and seem to be fine and like I said no codes. The fuel injectors were also tested and were perfect. The tranny was rebuilt and that was fine as well. It certainly seems electrical to me. So I was thinking it could need a crank sensor relearn, but what I undertand there is no option for that on a 98. The next think on my mind was the TAC module and or TPS. Do you have any suggestions for me.....Thanks a lot.... Tony
I had a 1st time customer bring in his 2000 C5 Auto for install of new heavily modified 409 L92 based engine that initially would allow me to do full throttle dyno runs but then started shutting down as I went past around 50% tp and around 5000rpm. The only sympton is just before it cuts out and when the tach approaches 5000, it starts to flicker between 5k and 6k. If it does do a full run the power curve is smooth even when the tach flickers.
The EFILive scan would lose coms at around 3200rpm and all pids would flatline, and I get a bunch of lost coms codes but no dtc,s. If i made it cut out a few times in a row it would set a p1514 (locked at fast idle). At the time the PCM had orig OS that would not do a case relearn so I changed to a 2002 C5 OS. It immediately set crank errors, I did a case learn and starting/Idle/ throttle response much better, so back on dyno to find it cuts out every time I go past 50% tp! So I reterminated all the ground points and fitted a another PCM, reflashed back to the 2000 OS with the cal that it did the good dyno runs. Oddly the nice idle etc stayed, the efilive scan doesn't drop out, the car drives very well but any more than 50%tp it cuts out.
At this point the owner gets around to telling me that the car has been cutting out ever since he had the transmission rebuilt and a high stall fitted!!! The Trans shop spent weeks trying to sort it out.
Common factor does seem to be the stall rpm, the first few dyno runs the stall was maybe 4200 but now its at least 5000. I know its way too high but he likes it. I'm thinking that there is a trans slip parameter that is being exceeded.
The owner wants me to M800 Motec the engine, that will eliminate the cutting out but if the trans is not happy now it will get really pissed...I want to find the reason for the cut out before changing anything.
Any info on the highest stall speed that has been successfully run in a C5? Or am I barking up the wrong tree?
Cheers
Tech Contributor
Joined: Dec 1999
Posts: 32,910
Likes: 2,402
From: Anthony TX
CI 6,7,8,9,11 Vet
St. Jude Donor '08
Did you find a solution for this problem?
I had a 1st time customer bring in his 2000 C5 Auto for install of new heavily modified 409 L92 based engine that initially would allow me to do full throttle dyno runs but then started shutting down as I went past around 50% tp and around 5000rpm. The only sympton is just before it cuts out and when the tach approaches 5000, it starts to flicker between 5k and 6k. If it does do a full run the power curve is smooth even when the tach flickers.
The EFILive scan would lose coms at around 3200rpm and all pids would flatline, and I get a bunch of lost coms codes but no dtc,s. If i made it cut out a few times in a row it would set a p1514 (locked at fast idle). At the time the PCM had orig OS that would not do a case relearn so I changed to a 2002 C5 OS. It immediately set crank errors, I did a case learn and starting/Idle/ throttle response much better, so back on dyno to find it cuts out every time I go past 50% tp! So I reterminated all the ground points and fitted a another PCM, reflashed back to the 2000 OS with the cal that it did the good dyno runs. Oddly the nice idle etc stayed, the efilive scan doesn't drop out, the car drives very well but any more than 50%tp it cuts out.
At this point the owner gets around to telling me that the car has been cutting out ever since he had the transmission rebuilt and a high stall fitted!!! The Trans shop spent weeks trying to sort it out.
Common factor does seem to be the stall rpm, the first few dyno runs the stall was maybe 4200 but now its at least 5000. I know its way too high but he likes it. I'm thinking that there is a trans slip parameter that is being exceeded.
The owner wants me to M800 Motec the engine, that will eliminate the cutting out but if the trans is not happy now it will get really pissed...I want to find the reason for the cut out before changing anything.
Any info on the highest stall speed that has been successfully run in a C5? Or am I barking up the wrong tree?
Cheers
I had a 1st time customer bring in his 2000 C5 Auto for install of new heavily modified 409 L92 based engine that initially would allow me to do full throttle dyno runs but then started shutting down as I went past around 50% tp and around 5000rpm. The only sympton is just before it cuts out and when the tach approaches 5000, it starts to flicker between 5k and 6k. If it does do a full run the power curve is smooth even when the tach flickers.
The EFILive scan would lose coms at around 3200rpm and all pids would flatline, and I get a bunch of lost coms codes but no dtc,s. If i made it cut out a few times in a row it would set a p1514 (locked at fast idle). At the time the PCM had orig OS that would not do a case relearn so I changed to a 2002 C5 OS. It immediately set crank errors, I did a case learn and starting/Idle/ throttle response much better, so back on dyno to find it cuts out every time I go past 50% tp! So I reterminated all the ground points and fitted a another PCM, reflashed back to the 2000 OS with the cal that it did the good dyno runs. Oddly the nice idle etc stayed, the efilive scan doesn't drop out, the car drives very well but any more than 50%tp it cuts out.
At this point the owner gets around to telling me that the car has been cutting out ever since he had the transmission rebuilt and a high stall fitted!!! The Trans shop spent weeks trying to sort it out.
Common factor does seem to be the stall rpm, the first few dyno runs the stall was maybe 4200 but now its at least 5000. I know its way too high but he likes it. I'm thinking that there is a trans slip parameter that is being exceeded.
The owner wants me to M800 Motec the engine, that will eliminate the cutting out but if the trans is not happy now it will get really pissed...I want to find the reason for the cut out before changing anything.
Any info on the highest stall speed that has been successfully run in a C5? Or am I barking up the wrong tree?
Cheers
Next is the drivers seat connector. Ive seen them broken and short out the serial data buss.
Last but not least is the STAR connector. Make sure that its clean and dry and not corroded. Pop off the top of the plug (shorting bar) and examine the pins carefully.
Next,, The TPS switch can be defective BUT,,,,like you said, NO CODES for that issue.
The TAC modules on 97 and some 98 cars had a TECH SERVICE BULLETIN on some being defective. The one in my 98 was bad and would cause the reduced engine power issue with codes. The cure was to up-grade to a 99+ TAC
BC
