I have checked continuity at the red-yellow wire that goes from battery power to the bank 2 VVT solenoid. When unplugged from the solenoid, I get about 45 ohms across the terminal and ground. This persists when I unplug the ECM, but when I unplug the circuit fuse, the resistance jumps to 1.6k ohms.
Looking at the schematic, I see that I shouldn't have a ground between this terminal and battery voltage.
Also in the schematic I see that fuse 16 also houses the VIAS, swirl, throttle position, and EVAP circuits, among others.
Of these, EVAP and TPS are of note. I am also suffering from a P1491, and sometimes when I open the fuel cap, I can hear air rushing in. The purpose of the EVAP vacuum cut valve bypass solenoid is to allow intake vacuum to suck on the gas tank for diagnostic purposes. However, it seems that this solenoid is getting stuck and allowing the intake to perpetually suck on gas tank vapors. I believe a short to ground would cause this, because there is no ground on this circuit aside from the ECM. In the past I have repaired frayed wires that were touching each other right beside the EVAP bypass, but that did not solve the P1491.
So how is this related to the VVT solenoid? Well, the vacuum cut valve bypass solenoid is wired directly to the EVAP purge volume control solenoid at the top of the intake. You can see this at the top of the schematic, it reads "To EC-PGC/V."
The wire for the EVAP purge volume control solenoid shares shielding with the bank 2 VVT solenoid, the throttle position sensor, and throttle position switch. (Side note, I have had the TPS take out the ECU in the past, which I repaired) Looking at the TPS schematic, I see that there is a shielding wire that surrounds one of the TPS wires and goes to ground at the main timing cover ground straps (F43).
So, I have a P0021 (bank 2 camshaft over-advanced) and a P1491 (vacuum cut valve bypass valve malfunction), two seemingly-unrelated problems that very conveniently share shielding. What I am thinking is that either they are shorting one another out, or they are grounding themselves on the TPS shielding. This is causing the VVT solenoid to malfunction, which is causing my cam to over-advance. It is also causing the EVAP vacuum cut valve bypass solenoid to stick open and apply vacuum to the gas tank.
Here are my typical bank 1 and 2 VVT solenoid readings. Bank 1 is the lower purple readout, whereas bank 2 is the upper blue readout. You can see that bank 1 is jumping around, presumably in response to the engine. Bank 2 stays pretty much steady.
What I'd like to know is whether there is a good way to troubleshoot this further before I cut into shielding. And is my electrical diagnosis even correct? In other words, am I correct in thinking that the red-yellow wire that goes to the VVT solenoid should have infinite resistance to a ground?
