Wednesday, May 26, 2010

P0521 - the Nightmare continues

Here's a recap of what's going on with my car:

Got a Stroker Built using VMS Cam Kit, Livernois Stroker Kit, & Melling Oil Pump. Took a few tunes to get where i'm at now. Had regular non-synth 5W30 from day 1, then after about 500-700 miles changed to 10W40. Atari's sat at 3 little blips at idle and at 5 blips (under the number '3') when driving all this time. Voltage usually for me sat around 10-11.

After 2 months(!) of flawless behavior driving with the car running just perfectly (minus I noticed the A/C not cooling) one day the Check Engine light comes on and my Atari's start showing '0' blips at idle and up to 3 or 4 when revving - The computer gives a P0521. Sensor Range error. I also notice voltage on the Atari's is now around 14?!?


  • Dealership checked wiring harness at Oil pressure sensor location and found no problems
  • Dealership replaced sensor, still the same problem.
  • Dealership put manual gauge on sensor hole and reads 'in spec' oil pressure. (numbers unknown)
  • Engine sounded just like before, and they had no other ideas so they sent me on my way so I drove it home, with at one time hearing a weird squealing noise (like a belt slipping).

Speed shop came to tow it just in case. They start testing things. Found a pulley/tensioner issue with A/C (probably what that squeal was) & recharged system.

Wiring harness looks OK. They read 18-25 psi at idle and up to 50 PSI revving , and SOMEHOW the atari's show normal again. CEL Went away. "ok Weird, but if it works it works" right?

They proceed to dyno after a few days. CEL comes back, Atari's read low again, computer now says 8-9 psi at idle (think < 10 psi is trigger for CEL?). Also now they lose the RPM Signal in the log and get some kind of crank sensor code.(P0335 and P0336)

They go over wiring & grounding again and say everything look good & tightly connected, and no visible pinching/melting etc etc.

Based on schematic, the Crank Sensor & Oil pressure sensor share 5V & Ground from the same source (ECM I'm assuming) so to me that looks like a possible clue..

I talked to a few people and opinions vary widely:

Kirk @ VMS Says: Probably Oil pump O-Ring ; But wouldn't it have been 'constant' - either from day 1, the time of picking up the car, or when 'whatever' happened to the engine (something broke?). I'm puzzled by the 2 months of perfect behaviour, then the problem which goes away by itself only to come back later in combination with another issue on top of it...

Andy @ livernois was saying "the pump blew up" or pickup depth wrong, or machined too loose, but all those sound like so catastrophic you'd either hear something, wouldn't drive around normally for 2 months, and you would NOT be getting normal oil pressure on a manual gauge..


Other suggestions have been: Oil Pump or Oil Pan pressure relief valve stuck open, Wiring harness damaged, ECM toast, etc, etc. At this point STILL nobody knows..


I'm having them retest the oil pressures manual & per computer back to back, and go over the harness with a magnifying glass to see what the heck is going on.. Next step to try is I guess getting a new ECM, and possibly dropping the pan anyway just to see if there's anything going on internally...