Drove 150miles today with no probs...hiway, side roads, plenty of power. Went for a short drive this aft, and on the way back, "REDUCED ENGINE POWER" msg flashes, then oil pressure starts to bounce, then drops to 0lbs before the whole thing just stalls. Power steering went weak as well, almost like the belt stopped turning - but thats just likely a result of the motor stalling?
Tried restarting and caught then lost oil pressure and stalled again. Oil level is good, elec is good. In the past when the msg flashed it was a result of a bent pin on the TB harness and I thot I had solved it. Anyway, after 15mins, restarted, oil pressure seemed close to normal, but was def bouncing back and forth 5lbs...idle felt stable, and TB msg stopped...ANY IDEAS WHAT i SHOULD LOOK FOR?

 

sounds like some sorta grounding issue? at least my guess...

 

Could a bad oil pressure sensor (or the wiring to it) cause something like that?

 

Hmmm....I did the new 4gg ground wire from engine to ground, and Alt to batt along with a new 150amp super fuse - but I left the old wires in place as well...so there shudn't be any ground issue...fact is I have just as much voltage bounce when the e-fans come on as I had before I did it!

 

I would be looking at a bad oil pump or sending unit. Can you hook a mechanical guage up to verify flucuation oil pressure before tearing anything apart.

 

If your sending unit checks out to be working then it is likely a problem with the pressure relief valve in the oil pump. I had zero oil pressure and that is what it was. I took the pump out, cleaned a bit of dirt out of the valve, cleaned everything up and put it all back together. It has been working great 10k miles (16k kilometers) later. knock on wood

I always suspect what I did last, so make sure to really check out the wiring you did on the grounds first. It may be worth while to undo it all and test. In other words really check thoroughly before you tear into the engine for a suspect oil pump.

Did a quick check in EFILive and it does not look like low oil pressure will cause REP mode. In my truck it flashed a Low Oil Pressure Warning and the bell went ding ding ding..... The truck would still run fine. Think it might be in your grounds or TB harness.

 

Let it sit overnite, went out and it started fine, good, normal oil pressure, then REP mode again...fiddled with the TB harness, key off, then restart and all operating normal. The wierd thing was that it seemed the belt stopped turning before it stalled cause my power steering went dead same time oil pressure dropped...thats why the whole thing sounds more like a ground prob and mech pump. I'll do what Mort said and remove/test the wiring work I did, and I'm gonna get a new TB harness. I have a spare TB as well, so might be worth it to change it all at once. I wont be able to get to it for a cpl weeks tho, so its gonna sit and hopefully repair itself for a while!
PS: Anyone have a link or part # for the proper TB harness fits 2004 Avv Z-71?

 

mine did the same thing . . but i was running.. at WOT.... were the street wet ?. . . they say it happens because a sensor gets wet. . i just turned mine off . . and everything back to normal...

 

Streets were dry...but I had just done a small burn out...R/

 

If it went into reduced engine power it has a code stored. Find out what it is then go grom there dont just start changing parts and assuming what may or may not be wrong.