355 Exhaust Bypass Valve Solenoid Wiring

I agree that this doesn’t make sense. My high resistance values appear good. My low resistance values do not. Your values have me scratching my head, especially if everything on your car is functioning properly. I don’t want to throw hundreds of dollars at a new TPS, but if we can assume the WSM gated values are the same as the F1, I do appear to be out of tolerance.

Of course, if the WSM values are simply the min/max of the potentiometer, we would be mostly concerned with the range of travel from idle to WOT on the car. It seems that without a proper Ferrari diagnostic computer, all we can do is compare values to see if anybody’s are way out of whack.

 

@Qavion here is the best I could do really quickly. Hope this helps. This was measured to a lug on the engine cradle with the battery disconnect switched to OFF. I also checked continuity on the 14-pin connector to the bypass valve connector. All checked out fine there while wiggling the connector.


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Not sure if this helps deduce the readings we are getting, but it looks like the TPS is supposed to react linearly (at least for the 001)

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Considering that, the range from idle to WOT should be quite similar between all of us. Maybe I’m misinterpreting that document. I’d still love to know if anybody else can read absolute throttle position % with a similar scanner. @Zamboniman308 ? That number may have sent me on a wild goose chase, but it really seems suspect. If the car is legitimately reading throttle position as 75% max, is the ECU calculating wrong or is the TPS being out of spec the problem?

If vacuum, electrical continuity, and throttle position all end up checking out ok, are we simply left assuming this specific feature of the ECU has gone bad?

 

I think I’ll take a trip to the store tomorrow to get a length of tubing I can attach to my vacuum gauge. Might as well drive around and see what I’m getting. Seems hard to believe the vacuum reservoir wouldn’t hold enough to at least momentarily open the valve as throttle increases, but I don’t know how much demand is on the vacuum system as a whole.

During all of the troubleshooting today,I did notice the rubber T connected to the idle air control valve has some cracks. Any possible relation?

 

That is indeed the question. Here’s what I could find:

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Hopefully linking to outside resources is allowed. Here is a manual that seems to explain how all of these parameters work. I’ll need to look at it with a clear head tomorrow to try to understand what I’m looking at.

https://www.scannerdanner.com/media/kunena/attachments/1222/GlobalOBDVehicleCommunicationSoftwareManual_EAZ0025B43B_2019-03-20.pdf

 

Yes, I think that would make the most sense.

I need to determine two things for certain:
1) Do I have adequate vacuum to the valve under all throttle conditions?
2) Is the open signal being sent to the solenoid under any conditions?

This would be easier to test while stationary, but I have read so many mixed anecdotes about whether the valve opens when revving in neutral.

 

Ran the vacuum test. Leave it to @yelcab to be right all along.

The setup (imperfect, but good enough to see what’s happening):
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Vacuum at idle (reduced to ~5psi with air injection off:
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Vacuum at full throttle and high RPM’s (poor angle because I just wedged my phone in the seat taking a video of the gauge while I drove and the gauge slid around):
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So now I need to figure out what’s leaking. I previously checked vacuum from at least the reservoir to the valve and it held just fine. I can’t remember how much further upstream I checked from there. Any obvious/common failure spots to check?

 

Now that I’m thinking back to the one time I heard the valve open correctly, it was when I downshifted to slow for a car turning in front of me, which would have driven vacuum up quite a bit. As soon as they were clear, I floored it and the valve opened. Makes sense that the valve opened immediately after engine braking.

 

Also, not sure why I was listing vacuum in PSI. Ignore my stupidity and read it as inHg.

 

I re-tested vacuum at the reservoir, which should test the reservoir and everything downstream until the solenoids and it didn’t hold perfect vacuum. It leaked down a little less than 1 inHg per second, which I think is good enough that it wouldn’t cause my issues.

It’s a tight fit getting to the rest of the upstream fittings and I think I’m going to have to put this all on hold until next month due to business trips. As a last test before I leave, I’ll probably try to recreate the conditions that caused the valve to open previously. High RPM engine braking, followed by immediate full throttle. If that works, I can say this is likely only a vacuum issue. I hope we at least learned a few things about the TPS along the way!

 

That’s a great question that I can hopefully get the answer to in the next few weeks.

As for my little test of building revs, letting off the throttle to build vacuum, then flooring it…well, the valve opened beautifully when I did that! Pretty well confirms a vacuum issue. I think this is good news.

 

Thanks!

Here’s a few photos after last week’s paint correction. Loving every minute of owning the car and getting it completely sorted. It is very close to being a trouble-free example.

 

I’ve been thinking about these check valves and whether they are working or not. While I was messing around with and checking all of the vacuum lines a few weeks back, I hooked up my little handheld vacuum pump to the reservoir end of the vacuum “supply” line that goes to the reservoir. I tried to pull vacuum on the end of that line and got absolutely nothing except the light smell of engine fumes.

I’m trying to wrap my head around this, but shouldn’t I have been able to pull vacuum against the check valves? I’m not sure if they use springs to hold a seal in place or what, but my simple brain thinks air shouldn’t be able to be pulled in the direction of the reservoir on these lines. It should only travel in the other direction. Do I have that right and did I see the problem early on, but it went right over my head?

Also, once air injection is shut off, the only thing the reservoir supplies is the bypass valve, correct? If that’s the case, there’s no reason it shouldn’t be holding enough air volume to operate the valve when the engine is not pulling vacuum.

Lastly, do Ferrari purists freak out if you throw a generic vacuum check valve on the vacuum lines? I’ll pony up for the real deal if it matters, but I might as well grab some cheapies in the meantime. I did see another thread where somebody added a single check valve (non-return valve) downstream from the factory ones, close to the reservoir. This may be easier unless it’s important for each of the valves to function separately and correctly.