RUDDER13

I just ported the TB on my 06 and put back on. Went for a test drive and about 5 mins in, 'Reduce Engine Power' came on. With my scan tool I checked and see code P0068, I reset it and eased it back to my house.

I have tried everything to resolve and now at a loss.

On a side note, when viewing the OBD2 data, while the car is off the TPS% is reading 26.3% and at idle 11.8%. Is that where is should be? Any other insight on this would be a huge help.

tennblkc6

while i don't have an answer to your question i believe you are going to need another tb. porting the tb on these engines are not for the novice.
good luck with it.

jim2092

Code P0068 is set when "the ECM detects that the current load and throttle position are not consistent with the expected load and throttle position". There are 9 diagnostic aids in the service manual for this condition.

One is "Any condition that can cause the MAF, MAP, and TP sensors to be shifted in value at the same time may cause this DTC to set." You may have this with your porting job.

RUDDER13

I went through all the DTC diagnostics on my scanner..I just am not sure how those values could shift off once the car was running. I can see shifting from pre port to after port and then having to re lean the positions of the sensors...but I have not had any luck with the 'Idle Re-Learn' procedures I have looked up. The car will not stay out of reduced power mode long enough to complete.

tblu92

P0068 is caused by a mis correlation between the MAF airflow and the airflow shown by the T-Body position-----Can happen mostly with very large aftermarket T-Bodies---Will put your car into limp mode--
Here is the best website for codes that explains it in plain English and goes thru several fixes---
http://www.gearchatter.com/viewpost14794.php
If nothing works seems like the only way to permanently get rid of it would be with tuning---Simply delete all the MAF sensor diagnostics--- as it's the MAF reporting that is causing the mismatch between the actual airflow and the predicted airflow--

jim2092

I would suggest contacting one of the forum vendors that do porting regarding what you may have done to cause this problem during porting. I have one such ported TB and it did not cause REP. Eliminating ECM diagnostics that would stop REP would not be my first recommendation as they are there to protect from various dangerous electrical failures, etc.

Zip Corvettes

This is a fairly easy fix. You need EFI live or HP tuners, go to diagnostics,
under the general tab there is a P0068 box, go to Max airflow Vs. RPM and create a histogram that matches this. Log the MAF g/sec into the histogram and then fix this table. Issue solved.

He is just flowing more air that what the ECM thinks it should. You do NOT want to disable any of it, but you can increase it to bring it inline with what the engine is actually doing, this way if there is ever an issue the ECM will catch it and put the car in REP the way it is supposed to.