• Got the Contributing Memberships stuff finally worked out and made up a thread as a sort of "How-To" to help people figure out how to participate. So if you need help figuring it out, here's the thread you need to take a look at -> http://www.corvetteflorida.com/forums/showthread.php?t=3581 Thank you, everyone! Rich Z.

Ground problem?

V

vetteguy61

New member
I may have a ground problem on my 2001 C5. Today while driving the check engine light came on followed by service traction control system followed by reduced engine power. Did a code check and had the following codes displayed.
10 PCM PO118, 28TCS C1278, 60 IPC B0251,BO RFC C2110,U1000,C1064. If it is a ground problem where do I start to check? Should I take it to the dealer and have them trace the problem. I have EFI Live tune so the computer can't be flashed. HELP!!!!!
 
Thanks for the info Rich. My car is doing the same as was posted in that link.Intermiiient and when I shut it off for a few minutes it's fine. I'll check the 2 front chassis grounds in a few minutes to see what they look like. Hopefully I can take care of it here at home.
 
Had my car at the dealer about the so called ground problem. They just called and said they can't find the problem. It is now time to get rid of it. Will be putting it up for sale next week.
 
vetteguy61 said:
I may have a ground problem on my 2001 C5. Today while driving the check engine light came on followed by service traction control system followed by reduced engine power. Did a code check and had the following codes displayed.
10 PCM PO118, 28TCS C1278, 60 IPC B0251,BO RFC C2110,U1000,C1064. If it is a ground problem where do I start to check? Should I take it to the dealer and have them trace the problem. I have EFI Live tune so the computer can't be flashed. HELP!!!!!
Click to expand...
What shape is your battery in? A weak battery, or bad connections can drive you crazy in the C5 and C6.
Andy :wavey:
 
The main ground points at the front of each frame rail are prone to corrosion but the ignition switch is a common culprit when the contacts burn over time. Both are not difficult fixes.
 
The battery is 3 months old. Voltage reads 14 volts when running. After all the money I had to put into the car to get it running after being at xtreme motorsports I just can't put anymore into it. All indications are a ground problem but the dealer can't duplicate the problem so they don't know where to start. I'm just fed up with having problem after problem just like Rich is having. It's not safe to drive when I don't know when it's going to go into reduced engine power and just barely runs when it does. I don't want to put myself in a position that will cause an accident.
 
Yeah, Mike I do know what you mean. But perhaps just storing the car for a while instead of selling it out of frustration might be the best thing to do.

Relying on a dealership to troubleshoot something like that might not be the best thing to do. If it were me, I would try to find a shop that specializes in electrical problems and let them take a shot at it first.

Have you talked to the people who last laid hands on your car?
 
I did talk to Brad in Pensacola last week. He said he never heard of that type of problem on a Vette. The 125 mile one way drive with this problem makes me very nervous about driving it that far. I have looked in PC for a shop that does electrical work and can't find any.I'm slowly running out of options on getting the problem corrected. I'm going to get my car from the dealer in an hour and see how it runs. The main problem is that I don't know when it's going to go into reduced power. There is no set interval on when it happens.Tried to explain that to the service advisor that there was no set pattern on when the problem occurs so it's pretty hard for them to duplicate.I would sure like to get it corrected so I can make the trip to Talladaga to run my 10 laps.Would hate to be driving around at 130 and have reduced engine power come on.
I'll make some calls when I get home and see if I can find someone who will take the time to find the cause of the problem.
 
Yes, once the codes are cleared the car goes back to normal. There is no set pattern onwhen it happens. it's done it while stopped at a red light, driving at speed 45 mph. So I can't pinpoint when it's going to act up.
 
If you need to drive a distance I would by a code reader for $100 and keep clearing it until you can get it to the guy that can fix it. The plus side the reader is nice to have.
 
Mike, have you located the ground points and cleaned them yet?

How long after the new tune did this start happening?
 
:banghead:Ok Here goes again. Had all the grounds and connections cleaned. That worked for awhile and started showing codes again, while driving or start up.The following codes are showing each time it goes into reduced engine power. P1120,P1221,C1278,U1000,U1064. I just replaced the throttle body with a brand new one. Car ran good for 4 days and today while going 50mph it went into reduced engine power.

Will I need to have my car retuned for the new throttle body? It replaced the same type of LS2 throttle body.
What else could be causing this problem?
Should I set fire to the car and let it burn?.:banghead:
Sure hope the experts out there can give me a place to start checking.
 
Jeez Mike, when I spoke to you a couple of days ago, I thought you had this problem licked. Damn... Looks like once "you know who" touches a car it's the kiss of death. We BOTH might be parting out our cars before this is all over with.
 
vetteguy61 said:
: P1120,P1221,C1278,U1000,U1064.
Click to expand...

DTC P1120

Circuit Description
The throttle position (TP) sensor is mounted on the throttle body assembly. The sensor is actually 2 individual TP sensors within 1 housing. Two separate signal circuits, low reference circuits and 5-volt reference circuits are used in order to connect the TP sensor assembly to the throttle actuator control (TAC) module. The 2 sensors have opposite functionality. The TP sensor 1 signal voltage is pulled up to the reference voltage as the throttle opens, from below 1 volt at closed throttle to above 3.5 volts at wide open throttle (WOT). The TP sensor 2 signal voltage is pulled down to low reference from around 3.8 volts at closed throttle to below 1 volt at WOT. TP sensor 1 and APP sensor 1 share a 5-volt reference circuit that is connected within the TAC module. TP sensor 2 and APP sensor 2 share a 5-volt reference circuit that is connected within the TAC module. If an out of range condition is detected with the TP sensor 1, this DTC will set and the Reduced Engine Power message will be displayed.

Conditions for Running the DTC
  • DTCs P1517, or P1518 are not set.
  • The ignition switch is in the crank or in the run position.
  • The ignition voltage greater than 5.23 volts.

Conditions for Setting the DTC
  • TP sensor 1 signal voltage is less than 0.13 volts or greater than 4.87 volts.
  • All of the above conditions present for less than 1 second.

Action Taken When the DTC Sets
  • The control module illuminates the malfunction indicator lamp (MIL) when the diagnostic runs and fails.
  • The control module records the operating conditions at the time the diagnostic fails. The control module stores this information in the Freeze Frame and/or the Failure Records.
  • The control module commands the TAC system to operate in the Reduced Engine Power mode.
  • A message center or an indicator displays Reduced Engine Power.
  • Under certain conditions the control module commands the engine OFF.

Conditions for Clearing the MIL/DTC
  • The control module turns OFF the malfunction indicator lamp (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail.
  • A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
  • A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
  • Clear the MIL and the DTC with a scan tool.

Diagnostic Aids
  • Inspect the TAC module connectors for signs of water intrusion. When water intrusion occurs, multiple DTCs could be set with no DTC circuit or component conditions found during diagnostic testing.
  • When the TAC module detects a condition within the TAC system, more than one TAC system related DTC may set. This is due to the many redundant tests that run continuously on this system. Locating and repairing 1 individual condition may correct more than 1 DTC. Disconnecting the components during testing may set additional DTCs. Keep this in mind when reviewing the stored information, Capture info.
  • If this DTC is determined to be intermittent, refer to Intermittent Conditions .
Click to expand...

DTC P1221

Circuit Description
The throttle position (TP) sensor is mounted on the throttle body assembly. The sensor is actually 2 individual TP sensors within 1 housing. Two separate signal, low reference and 5 volt reference circuits are used in order to connect the TP sensor assembly to the throttle actuator control (TAC) module. The 2 sensors have opposite functionality. The TP sensor 1 signal voltage is pulled up to the reference voltage as the throttle opens, from below 1 volt at closed throttle to above 3.5 volts at wide open throttle (WOT). The TP sensor 2 signal voltage is pulled down to the low reference from around 3.8 volts at closed throttle to below 1 volt at WOT. TP sensor 1 and APP sensor 1 share a 5-volt reference circuit that is connected within the TAC module. TP sensor 2 and APP sensor 2 share a 5-volt reference circuit that is connected within the TAC module. If an out of range condition is detected with the TP sensors, this DTC will set and the Reduced Engine Power message will be displayed.

Conditions for Running the DTC
  • DTCs P1517, or P1518 are not set.
  • The ignition switch is in the crank or run position.
  • The ignition voltage is greater than 5.23 volts.

Conditions for Setting the DTC
  • TP sensor 2 disagrees with TP sensor 1 by more than 7.5 percent.
  • All above conditions are present for less than 1 second.

Action Taken When the DTC Sets
  • The control module illuminates the malfunction indicator lamp (MIL) when the diagnostic runs and fails.
  • The control module records the operating conditions at the time the diagnostic fails. The control module stores this information in the Freeze Frame and/or the Failure Records.
  • The control module commands the TAC system to operate in the Reduced Engine Power mode.
  • A message center or an indicator displays Reduced Engine Power.
    Under certain conditions the control module commands the engine OFF.

Conditions for Clearing the MIL/DTC
  • The control module turns OFF the malfunction indicator lamp (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail.
  • A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
  • A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
  • Clear the MIL and the DTC with a scan tool.

Diagnostic Aids
  • Inspect the TAC module connectors for signs of water intrusion. When water intrusion occurs, multiple DTCs could be set with no DTC circuit or component conditions found during diagnostic testing.
  • When the TAC module detects a condition within the TAC system, more than 1 TAC system related DTC may set. This is due to the many redundant tests that run continuously on this system. Locating and repairing 1 individual condition may correct more than 1 DTC. Disconnecting components during testing may set additional DTCs. Keep this in mind when reviewing the stored information, Capture info.
  • If this DTC is determined to be intermittent, refer to Intermittent Conditions .
Click to expand...

That will give you a start, Mike. I've been reading about the codes you have and I think maybe you need to be looking for a TAC module as well. I think both of our cars were sitting too close to each other for too long.
 
That's some good info Rich until it kept on saying Tac module. I better start looking and see if I can find one somewhere. Yes they must have been too close to each other. They have the corvette cooties.:lmao:
 
Well, obviously the world has run out of those TAC modules, so it seams that they must have a fairly high failure rate.

Just hope that if it IS your TAC module, that it doesn't get to killing your PCM for you. Apparently it CAN do that.
 
I had same problem did a search through google and found lots of help but it came down to replacing the computer and no problems since then. By the way it is not cheap but you can buy rebuilt modules check out google with your code numbers you get.
 
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