P0521 code - again
Hello all, long time reader, newbie member here.
I have an unusual P0521 code issue that does not seem to match any of the other posts on the forum - Iím hoping someone can help...
Iíve recently gotten a P0521 code. I realize this is not a pressure code but rather a signal code indicating too many/too few signal variations, however, I did check the pressure with a gauge. At operating temperature PSI at idle is >15 pounds and at WOT/6k RPMís the pressure is ~70 PSI. The pressure is steady at all RPMís with no significant gauge fluctuations indicating a smooth pump and/or relieve valve operation. As a result, I changed the PSI switch and filter screen under the switch. Within 30 miles of replacing the switch, the light came back on. After further testing with the mechanical gauge and days of running with it installed, I have not seen a single issue with the pressure or pressure stability that concerns me. On the forum Iíve seen filters replaced, assumptions that the DOD/AFM turning on all have an impact on the code - so, Iíve changed the filter and I updated my tune to a DOD delete version to ensure it never activates and impacts the pressure. I cleared the code, drove ~ 30 miles and the code is back.....
Since Iíve been chasing this fault, I now have another interesting issue. Within moments of the CEL coming on, I now get a tire pressure system fault indicator and all 4 tires have the dash vs. the PSI. They seem linked because I get one then the other - seemingly the CEL always followed by the TPS system fault.
Of all things, when the prior 2 faults rear their heads, my brake performance changes drastically!?!? When those faults appear, the point where my brakes engage in the pedal travel drops and it feels like only/mostly the front brakes are operating and the car takes longer to stop and nose dives significantly. The obviousness of this is the dangerous factor here which makes me VERY uncomfortable driving the car.
When I clear the code everything returns to normal for about 30 miles and then the cycle repeats itself....
About a year ago I had a headlight issue which was related to a corroded ground on the passenger frame rail in the engine compartment. I rebuilt the ground, and now with the recent issues, Iíve removed every ground cable, cleaned the surface, chased the threads reinstalled the ground and then used liquid electrical tape to seal the ground point. I used an OHM meter to verify the integrity of every ground and all check perfect (this did REDUCE but did not eliminate the damn stereo whine when using the AUX cable... which indicates I still have a ground loop somewhere...).
Because of the seemingly unrelated faults and the history of a ground issue - I still assume this is also a ground related issue, so my asks are:
- Has anyone ever had such issues?
- Does anyone have a wiring schematic for the engine control systems?
- Does anyone know if the engine control module, body control module and electronic brake control module share a common ground and where it is?
- Does anyone have other suggestions?
Thanks in advance!