ANOTHER reduced engine power incident.

[JLE58]

This is a Easy fix with a good meter and know how on Dc circuits. Your EcM is sending out 5 volts to a number of sensors "5 i believe" for some reason you ecm is not seeing that 5 volts. The p0651 code means the circuit is Open. So you dont have a problem with low or high voltage you have an Open circuit somewhere.

[JLE58]

Since you said you were getting the fault with the wheel hop I would be looking at the fuel sensor. I believe the p0651 is the B side and i believe that sensor is on that side. So it would seem if you had wheel hop it was shaking the connection enough to open the circuit. It only needs to lose this Signal for 2 seconds to get a fault. You could also pull over and let the car cool down and start the car a few times if the fault is not still there the computer will reset and take the car out of limp mode.

[NipTuckTaxi]

i can get it out of limp mode with the SCT and/or a restart.
the car runs normally but the check engine light stays on and the code will not clear.
the moment i floor the accelerator/the car goes into limp mode.
a few days earlier i had a throttle position sensor code. it cleared fine. i also changed to a ported throttle body prior to this happening.
the evening i floored it from a dead stop and got the wheel hop is when the 5volt circuit out of reference code started and will not clear.
it seems to be a hard one to nail down. im flabergasted with it.

[hoffmk2003]

Originally Posted by NipTuckTaxi

I just installed one a few hours prior to all this. First. Time wot and bam. I got stabiltrak service message and reduced engine power. I can get 8cylinders back as long as I don't get aggressive. If I do then its back to reduced power.

Your ported throttle body and other mods are you problem, that is why you are getting the REP mode. the computer is seeing more air coming in than it is expecting to get........

Get the REP codes deleted from your computer or tune the REP mode tables..

I don't care about REP so I just blew away the codes to disable them......no problems for me. I got this the first time I installed my vararam and my full exahust.

Ken

[MikeOD]

Originally Posted by hoffmk2003

Your ported throttle body and other mods are you problem, that is why you are getting the REP mode. the computer is seeing more air coming in than it is expecting to get........

Get the REP codes deleted from your computer or tune the REP mode tables..

I don't care about REP so I just blew away the codes to disable them......no problems for me. I got this the first time I installed my vararam and my full exahust.

Ken

I'm actually surprised I've never run into an REP issue on my car yet...I think I have basically the same drivetrain as you, LS3, tune Vararam, 1.875" headers and 3" exhaust...

I agree though, sounds like it's the issue, have the conditions for it adjusted or disabled...assuming the car drives ok when you aren't hard into the throttle...I think REP becomes much more common with a cam swap.

[JLE58]

Originally Posted by hoffmk2003

Your ported throttle body and other mods are you problem, that is why you are getting the REP mode. the computer is seeing more air coming in than it is expecting to get........

Get the REP codes deleted from your computer or tune the REP mode tables..

I don't care about REP so I just blew away the codes to disable them......no problems for me. I got this the first time I installed my vararam and my full exahust.

Ken

You got a p0615 code?

[JLE58]

p0651

[JANNETTYRACING]

Originally Posted by MikeOD

I'm actually surprised I've never run into an REP issue on my car yet...I think I have basically the same drivetrain as you, LS3, tune Vararam, 1.875" headers and 3" exhaust...

I agree though, sounds like it's the issue, have the conditions for it adjusted or disabled...assuming the car drives ok when you aren't hard into the throttle...I think REP becomes much more common with a cam swap.

Having tuned over 600 cars I have never run it to it so I beleive this is unique to this car and an intermittent circuit problem based on the description of the code.

I would be open to turning off the code but that just covers up the problem and does not Fix the problem.

You don't put a band aid on a broken leg.

Ted.

[hoffmk2003]

Corrected You are going to want to solve the electrical issue first then see if it still goes into REP. If it does with no codes in the computer disable REP

Ken

[JANNETTYRACING]

Originally Posted by hoffmk2003

with due respect Ted, check over at HPtuners site etc... Lots of folks have had this problem across multiple GM platforms when doing mods that effect air flow into the engine. It ususally comes up more with folks who are running FI or HCI etc.

I am not 100% on all the purposes of the REP mode but if it is happening at WOT everytime then I think it is safe to say it is not intermittent and is repeatable. I have read that it is there in the event of a stuck throttle blade or something other run away event as a safety measure. Some guys have sucessfully tuned for REP with their mods using HPT. I however have opted to just turn it off as I feel I am a competent driver and don't need the PCM telling me how many cylinders I can have running. When REP mode kicks in after a WOT throttle jab it is a major problem, I almost got rear ended because the car fell on it's face and had next to no power. It's causes more problems than it is worth. So I disagree it is a band aid turning it off, much like turning off CAGS routine for skip shift is not a band aid.

the other possible cause is the straight shot intake we are both running, the vararam design changes some of intake dynamics most notably increasing airflow into the engine dramatically. Now vararam has done their homework on these intakes, they aren't as simple as they look they spent some coin developing that intake to flow correctly and minimize turbulance etc via CFD analysis they paid some R&D company to do. So i'm going to venture to say it's not a bad intake design contribuiting to this problem but rather a GREAT intake design which flows VERY well....possibly too well for the factory REP settings, whatever they are.

Ken

I am well aware of what causes REP and your right it is mostly forced induction cars that will set this.

Drive by wire is the reason for REP, when the computer sees a change in Airflow VS Manifold Pressure VS Accelerator pedal position out side of an acceptable range it goes in to REP.

It is checking to make sure the Drive by wire Throttle is doing what it is suppose to, it is a SAFETY FEATURE WE DON'T TURN OFF.

Loss of the 5V reference will set this also which is what is happening in this case.

There is no need to turn the code of if the tables are tuned correctly for the FI application

This car is NA with simple bolt ons which in my experience has never had this problem.

Ted.

[JLE58]

Originally Posted by JANNETTYRACING

I am well aware of what causes REP and your right it is mostly forced induction cars that will set this.

Drive by wire is the reason for REP, when the computer sees a change in Airflow VS Manifold Pressure VS Accelerator pedal position out side of an acceptable range it goes in to REP.

It is checking to make sure the Drive by wire Throttle is doing what it is suppose to, it is a SAFETY FEATURE WE DON'T TURN OFF.

Loss of the 5V reference will set this also which is what is happening in this case.

There is no need to turn the code of if the tables are tuned correctly for the FI application

This car is NA with simple bolt ons which in my experience has never had this problem.

Ted.

Exactly.

[JANNETTYRACING]

If I had to take a wild guess BAD GAS PEDAL the vibration from the wheel hop is shaking it's brains out.

Ted.

[chriscamaro69z28]

i had the same problem when i installed a ported throttle body but as soon as i put my stock one back on it was fine some say the weak maf sensor maybe the issue not compusating for the increased air

[hoffmk2003]

from the HPtuners forum......might want to check your connector going to your TB.....

I know after about 80,000 miles my truck started going into this mode. It progressively got worse. First code thrown was throttle body performance code. I replaced the throttle body under warranty then a couple months later it happened again. Come to find out these trucks have a problem with the plug that goes into the throttle body. The wires are a little tight and it causes bad connections. The plug costs about $50 from the dealership and comes with a foot of wire and heat shrink butt connectors. I replaced the plug and haven't had any problems since then."

Ken