X-ZZ4

My car is falling on it's face when I attempt to accelerate. If I feather the throttle.....it is drivable (barely), but there is no boost. But any normal acceleration, it falls on it's face, wants to die, and throws codes.

Here's the codes.....

#1 - 16490 - Manifold Pressure / Barometric Pressure Sensor (G71) / (F96), Implausible Signal
#2 - 17956 - Boost Pressure Regulation Valve (N75), Open Circuit
#3 - 16620 - Manifold Pressure / Boost Sensor (G31), Implausible Signal

I'm thinking for $100 I'll just try the N75. Any other suggestions?

jcman

Not an expert on the 2.7t but generally when this one comes across the forum it's a problem with a rubber hose leaking somewhere in the plumbing, if you don't see a loose hose the N75 "Open Circuit" code seems logical for replacement as the other two codes are a following result of this.

X-ZZ4

Thanks. I've been replacing hoses and troubleshooting vacuum/boost leaks. It was running good until this started. I've been meaning to do the spider hose....and when this started I figured I should do that and hope. The spider hose helped alot with idle, etc....but I still have this issue.

I'll look again for leaks (and frayed wires).....but that "open circuit" thing is what is really pushing me towards thinking the valve itself has died.

jcman

Your welcome.
I think a new part is in order too.

X-ZZ4

Got a chance to do the N75 this morning. Yep.....$100 down the drain. No change.....oh well....one more possibility eliminated....LOL

I did drive it a bit harder this morning. If I keep on it a bit after it recovers from falling on it's face......it will build boost above 3000 RPMs. Not smooth.....but it is definitely boosting. I didn't put a gauge on it, saw no purpose because I ain't staying on the throttle long running like this. But it felt like a decent amount of boost.....fairly normal.

Same codes. Suggestions?

jcman

Drats!
I know it's a after thought and I didn't have the info until now "sorry" but the N71 tested with a Volt Ohm meter should read 20 to 30 Ohms @ 68 degrees Fahrenheit, at least you will know if it failed "or" a connection has in the harness, plug or ground.
I tend to look at DTC's in an order that one can cause others and the Implausible Signal used to trick me into thinking something else when it just means a monitored signal is Out of Range, the Open Circuit code description is straight forward.

Prospeeder

I believe there should be voltage at the N75 and then the ECU pulses the ground. You should make sure its got the voltage with key on. And then check continuity from the N75 ground to the engine computer connector.

Just Me

I'm currently in the process of replacing ALL of mine. (S6)