What is this Power Reduction message on my display?

[540gts]

I have search for power reduction on forum with no results. 04 LQ4 6.0 2 wheel drive, it looses power for awhile then recovers. What it Power Reduction mode?

[mowton]

Power reduction mode is a protection feature to "save" the engine, tranny or driver depending on the conditions. It automatically limits your throttle and/or fuel to prevent runaway. Good examples of conditions to set REP is if the PCM senses more air being ingested than allowed for a specific RPM or throttle opening. If you google, you should find info on it. Lookup DTC's like P1514, P0068, P0121 or P0106 for starters.

Normally you have to restart the car to get it to go back to normal mode.

Post a log and tune when the event happens.

Ed M

[nkautz]

Check your DTC codes and look them up

[540gts]

After the "Reduced Power Mode" came on it showed PO332 and PO1516, one is knock sensor the other has to do with the throttle body, you were right there is tons of info on the net. Sometimes they can fix them other times they don't? Does anyone have any personal experience with this?

[nkautz]

Are you supercharged or turbo?

[mowton]

The 1514 is the easy one......I hope :-) Go to Engine Diagnostic>General>TPS Sensor...Calc Airmass, TPS/RPM and MAF Cylair, make sure your setup isn't exceeding any of these parameters based on the engine speed and throttle position. Best way is to log the 3 parameters and run through the ranges to determine the actual levels. Set up 3 histograms similar to the tune tables makes it pretty easy. Then add like 10to 15% to those levels and repopulate the tables.

Knock sensor is a bit harder. Do you have the LS1 or LS2 knock sensors installed in your setup?

Ed M

[nkautz]

He's getting 1516 , which is either a wiring issue or throttle body, from what I've seen. One of the P151X codes is solved by scaling IFR/VE/Spark by 1/2 , I forget exactly which code though. It's from exceeding CylAir max (1.2g/cyl). But that usually only happens if you're making more than 600whp. But yeah it's a good idea to max out TPS Sensor "Calc Airmass" and "MAF Cylair" tables. Also max out "P0106 Error Max" and set all 0's in "P0106 Error Min"

[mowton]

He's getting 1516 , which is either a wiring issue or throttle body, from what I've seen. One of the P151X codes is solved by scaling IFR/VE/Spark by 1/2 , I forget exactly which code though. It's from exceeding CylAir max (1.2g/cyl). But that usually only happens if you're making more than 600whp. But yeah it's a good idea to max out TPS Sensor "Calc Airmass" and "MAF Cylair" tables. Also max out "P0106 Error Max" and set all 0's in "P0106 Error Min"

Thought I read 1514.....senior moment :-) I didn't see any mention of power adders so exceeding 1.2 g/cyl would need to be confirmed by the OP.

I agree about scaling the airflow if you add like FI and exceed the MAF 512 g/sec limit. Or you could tune in SD to get more airflow room. But, I don't believe you should just "max out" TPS safety parameters if you can set them as OEM engineers intended. Set up the histograms like I said above and log the values your setup generates, add a bit of buffer and repopulate tables accordingly. Last resort is to max or shut off codes. They are there for our safety.

Ed M

[540gts]

It is a stock 04 6.0 2500hd, It runs so good until it goes into POWER REDUCTION MODE, It never gets drove hard. I have read everything from connecter problems to TB problems and one said his only did it in cold weather. I will spend a couple hundred to fix but after that, I will eliminate codes. How foolish would that be?

[nkautz]

Throttle body faults like P1515 and P1516 will still cause REP (reduced engine power) even if you disable the codes in the tune. To solve , you have to figure out whats causing the fault in the first place by process of elimination. I was getting P1515 every other time I stomped on the throttle hard , I tried changing the harness , everything I could think of in the tune , and finally replaced the throttle body and now it only does it like 1 out of every 20 times.

[540gts]

I hope it is the T body I have one on order be in tomorrow, I check the wiring today, it all looks good.
I will post results when I find solution.

[540gts]

Throttle body fixed it, bought a new NAPA auto parts # ETB103.
Previously I had codes P0120, P0220,P1516,P2135 none have come back yet, not sure how all of these relate to the Tbody.

[nkautz]

Thanks for posting the solution.