Reduced engine power mode question
Thread Starter
Racer
Joined: May 2008
Posts: 254
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From: Plant City Fl
Reduced engine power mode question
I'm frustrated with this. The last two times I've driven my car it has gone into reduced engine power mode/service active handling during my LONG drive home. It seems to happen when I hit 90mph. Just had O2/knock sensors replaced maybe 3k miles ago, Z06 has 110k on it with head/cam swap. Going to check the grounds but I'm throwing no codes besides the ones that are archived/history codes. I'm sure I'll be burned with "it's called a search button" comments; I deserve them but I did do a forum and Google search, but found no situations like mine. They're all throwing codes you would expect with it and mine is not, just horn relay. Any help or insight would be appreciated. Going to try and check the tb tonight. Thanks for your help
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
I'm frustrated with this. The last two times I've driven my car it has gone into reduced engine power mode/service active handling during my LONG drive home. It seems to happen when I hit 90mph. Just had O2/knock sensors replaced maybe 3k miles ago, Z06 has 110k on it with head/cam swap. Going to check the grounds but I'm throwing no codes besides the ones that are archived/history codes. I'm sure I'll be burned with "it's called a search button" comments; I deserve them but I did do a forum and Google search, but found no situations like mine. They're all throwing codes you would expect with it and mine is not, just horn relay. Any help or insight would be appreciated. Going to try and check the tb tonight. Thanks for your help
Well,,,,,,,,,,,,,,, As with any Reduced Engine Power (REP) issue,, it usually deals with the THROTTLE BY WIRE system. If ANYTHING in that system TPS, APP, TAC Module fart wrong, it will go into REP Mode.
DTCs. Just saying you have the USUAL DTCs or History DTCs means nothing. ALL DTCs are "important" for trouble shooting purposes.
I recommend that you CLEAR ALL the DTCs. When the car goes into REP, use the RESET BUTTON to clear any DIC messages. Then BEFORE YOU TURN THE IGNITION OFF read the DTCs. List ALL of those DTCs that you see in that ignition ON cycle. Doesn't matter if there Current, History, U series, or No Comms. List them! Its important for proper troubleshooting!
If you have a REP issue,, TRUST ME,, there will be related DTCs.
On the other hand,,, If your tune is wrong or you have a massive MAF to Throttle Body leak or the engine thinks that the throttle angle is wrong for the amount of air that going through the engine, it can and will go into REP Mode!
Let me know what you think and if any of this gets you on the right track.
Some other NOTES and THOUGHTS.
1. The Throttle by wire SYSTEM does NOT use chassis grounds. All the sensors use discrete wires to get the signals to and from the modules. A signal ground is called LOW REF.
Its much different than chassis / earth ground to the modules them selves.
2. When you go into REP Mode, are there ANY IPC related errors, weird gage readings that happen during this mode??
Thanks for serving brother!
Bill C
