16490 - Barometric / Pressure Sensor Code

I experienced what appeared to be some turbo issues today (lack of). Sure enough, my engine thru a code: #16490 - Barometric / Pressure Sensor (G71) / (F96): Implausible Signal. After performing a "search" it appears that the N75 valve may be the culprit.

The snow screen, air filter, intercooler, air stream is clean. MAF replaced ~10k ago.

I would appreciate any advice or direction.

Thanks,

Hi,

The baro sensor lives inside the ecu and tells the ecu to adjust power to varying elevations from 0.5 bar to 1.0 bar.

The map (manifold absolute pressure) sensor is located in the boost pipe and tells the ecu actual boost presure. If you get fault codes for boost deviation, it could be boost leak - intercooler/hoses, n75, vaccume leak (vac pump), or hose leading to vnt actuator. Stuck vnt actuator can smoke too or in some cases cause overboost all the time.

Rule of thumb - If your car is smoking heavily with loss of power, you may have a boost leak or could be a bad turbo. If there is no power and no smoke, it's probably the maf (mass air flow) sensor.

Jeff

Symptoms:
While highway driving two days ago I noticed a sudden loos of power. MIL on (16490). Can't clear it. Does not appear on start up. Appears at about 1500 rpm (I assume when turbo is being loaded). Car drives ok on back roads (low rpm's), but when I give it more throttle it does not perform (feels like no turbo). Car struggles up hill and has a hard time maintaining 65 mph on the highway. I do not notice any smoke at any rpm.

Here's what I've looked at so far:
Cleaned snow screen, air filter.
I checked all of my intake air connections - all ok.
I removed and cleaned the N75 and reinstalled - thru MIL on my test drive. Next I swopped my MAF with a good spare that I had - still thru MIL on test ride.

I don't think it is an air intake leak. I checked everything and I know what those leaks sound like (I buggered one of the intercooler hose clips when I did my timing belt - very audible).
I don't think it's a vacuum hose leak because the loss of power was somewhat sudden.
Without the help or advice from anyone, I think my next step would be to replace the N75. Does anyone know how to trouble shoot of those things? Or give me any advice? Thanks,

Another update:

I read this post from rmr25 and decided I'd give it a try:
"I recently encountered some boost problems on my 2000 Golf GL. One excellent test to determine that the turbo's vanes are moving correctly is this: With the engine running, in VAG-COM go to Group 011. This will show what's happening with the N75 valve, which controls vaccuum going to the turbo. Down in the lower left of that VAG-COM page is "basic settings." Click this on. You'll see the N75 go "off" and "on." Then, put a light down against the lower firewall (just in front of where the passenger's feet would be) and position a mirror so you can see the back of the turbo. As the N75 cycles, you'll see the VNT actuator rod move up and down, about 3/4" each way. If this test is ok, you can assume that both the N75 and the turbo are working ok. That'll at least eliminate them as problems."

So in Basic Settings, Group 011, I witnessed the N75 go "on" and "off". I also witnessed the actual vnt actuator rod stroke in and out abour 3/4" many times. So is it safe to say that my N75 and vnt are ok? Now what?

Post Mortem:

Turbo is back and MIL is gone! After I wrote my last post I went to the store and my turbo is definately back. I can squeal my tires again. The MIL did come on but the performance was back. When I pulled into the garage I plugged into VAG COM again but this time it let me clear the fault code (could not before).

My guess is that when I dooshed the N75 it did clean something out and when I did mrm25's test I was actually watching it performing correctly (abviously).

I'm going to change my oil this week and I think I'll put her on the ramps and investigate / oil the vnt actuator and linkage.

Merry Christmas

I am experiencing these same symptoms. I rplaced my N75 with a known good one from a buddies car, and performed the group 011 test, and the VNT is moving / operating properly.I don't see alot of smoke, but I definately have power loss and a MIL. Anybody got ideas on what I should check next? I am getting ready to take a 6 hour road trip to Richmond, VA and back to Wichester, hopefully this will clear up during the trip with the replacement N75, if not, there may be a TDi with a blown Turbo sitting on the side of Rt 17 or I95 this afternoon.

OK, just pulled the MAP Sensor and cleaned it. It seemed to help some, but MIL is still on. I'm gonna take it to Richmond and see what happens.

That code is for the manifold pressure sensor, on your '02 car it should be located on the intercooler. A search on "MAP + CEL" reveals threads that indicate this part is not generally prone to failure. I'd look for loose, cut or disconnected wiring by the intercooler. If the wiring checks out, see what a dealer wants for a MAP sensor on a Saturday...

Additional note: the Bentley says that 16490 means "Manifold Abs.Pressure or Bar.Pressure Range/Performance", which would likely rule out faulty wiring, as there are additional codes for voltage supply and high/low input. Time to call some dealers to see if they have a MAP sensor, or maybe borrow your friend's to verify that is the problem.

Thanks!! I actually pulled the MAP and found it had a fair amount of oil on it. I wiped it with a clean shop towel and blew out the pressure sensor part (which I believe is a tiny hole next to the temperature probe). Took it for a drive and still had the CEL, but once I got on the road, CEL went off and power returned to normal. I am going to put the original N75 back on, and drive it. If it happens again immediately, I will order a new N75, if it happens again in a couple days or weeks, I'm going to order a new MAP Sensor. I plan on pulling th IC this coming weekend and empty the condensed oil out, when I do my 70,000 Mile service.

I lost my turbo and threw the same code again! This time I visually inspected the VNT while the car was at idle and it appeared to be working perfectly. So knowing that the N75 and the VNT were ok I decided to inspect the G71, Barometric / Pressure Sensor located just after the inter cooler (you have to remove the windshield washer resevior to get to it...)
This sensor was absolutely plugged with oil and crud. It was dripping with oil. I removed and cleaned with brake cleaner, reassembled, cleared code, and car runs fine. I think I'll get a spare G71 and replace it one of these days.

Whats interesting is that I removed the source of oil in the intercooler and cleaned it at 40k miles. It shows you that no matter what you have done with your CCV or when, this sensor can get crapped up enough to throw a code. I never have removed, inspected or cleaned this sensor before.