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The Limp Mode Ghost

2K views 7 replies 5 participants last post by  Twoodgt 
#1 ·
So for a couple weeks now anytime I use M mode and hit over 6 to 7 thousand rpms I get the old engine malfunction along with DSC AND DBC warning lights. Limp mode follows shortly there after. I stop cut the car off and restart it and alls good. All problems were pointing to a bad throttle actuator. But I discovered that if I’m not in M mode I have the full 400 hp all the way to red line without any problems at all. I would think that if an actuator were bad that it’s bad regardless of what mode I’m in. To add to the confusion the other day I decided to change from P500 plus back down to just P500. I drove the car for a day or two in this mode and yesterday I changed it back to p500 plus. Now for some reason my car pulls and drives like a brand new car. No limp mode in any mode and no codes WTF ?!?! I have a few upgrades and I was thinking that I was have an issue with one of those also. I have the ESS computer upgrade as well as the SMG upgrade with speed limiter removes and underdrive pulley. I also have the Rpi scoops and Super Sprint Exhaust (from headers back). I don’t know what’s going on but I did go ahead and order new gears for the Throttle Actuators just in case. I’m going to freaking enjoy it now unless old limp mode comes around again soon !!! If any of you can explain this please help a brotha out !!! Thanks
 
#2 · (Edited)
Pull the codes...

but 400 hp works by limiting the fill , ie throttle to 80% and 500 hp mode the throttles don't open 100% below certain rpms( not in front of the tuning computer to tell you which exactly). So it's possible you have broken/missing tooth on the actuator btw the 80%-100% open range.

oth the actuators do self test not sure the exact criteria of that though.
 
#6 ·
I appreciate both answers. I sorry I didn’t mention. I pull the codes I can’t remember that actual code but one was the idle speed actuator and another was for clutch adaptation (I have had this one for a year). And of course the normal DBC and DSC malfunctions that are activated durning lisp mode. I had all the injectors replaced about 2 months ago because #5 was stuck open and hydro locked the engine and broke 2 starters (1st one was replaced before the mechanic knew what was going on). No fuel codes and not throttle actuator codes. But like I said after switching to P500 plus back to p500 only and then back to P500 plus again a few days later it pulls and feels like it has more power now than it has since I have had it.
 
#8 ·
No that is not the case. I made mention of the injectors being replace because of one of the other members made a comment about fuel starvation. The car ran fine up until 2 weeks ago. I was on the interstate and drop it into 4th gear. I ran the rpms up to about 7500 and bam limp mode. I pulled over and shut it down. Once I restarted it the car ran fine unless I ran the rpms up again. I came home and pull the codes I got the normal DSC AND DBC faults along with the engine malfunction code. The only code that stood out was the U1139 idle control valve/AMT Communication Bus off the OEM code was CD8B Bus off Idle Speed Control Valve / SMG Can. I changed the fuel filter this weekend hoping it was only a fuel starvation issue but the symptoms stayed. But as I stated about if I ran the car with out activating M mode I have full rpm etc with no codes or limp mode being activated. So yesterday I decided to attempt to change my M settings from P500 Sport to P500 just to see if that would do anything. I went for a test drive and it continued to malfunction. A few hours later I change it back to P500 Sport. Once I did the car had more power than I can ever remember without limping out at any rpm. I don’t know what the deal is. Hope that cleared it up a little.
 
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