Ground problem?

[vetteguy61]

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.

[Sub-Zero]

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.

[Rich Z]

Mike, have you located the ground points and cleaned them yet?

How long after the new tune did this start happening?

[vetteguy61]

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?.
Sure hope the experts out there can give me a place to start checking.

[Rich Z]

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.

[Rich Z]

Originally Posted by vetteguy61

: P1120,P1221,C1278,U1000,U1064.

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 .

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 .

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.

[vetteguy61]

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.

[Rich Z]

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.

[vetteguy61]

That's all I need. I can see the $$$$ signs flash before my eyes.

[Scully]

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.