355 Exhaust Bypass Valve Solenoid Wiring

Yes, when properly adjusted, the throttle linkage will hit a hard stop (making a clicking sound) when the plate is in the perfect vertical position (full opening). The eight independent throttle plates are synchronized so it is not advisable to go in there and start adjusting things without proper equipment.

 

I was going to suggest this same direction. Need to pull the cover and tank. Its a lot of work but you really need to get the top off to see it and get it to a good starting point. Plenums off even better but that is a LOT more work. I have mine off now since I pulled the injectors for cleaning. Was nice to visually inspect the throttle linkages clean the throttle plates etc. im about to do a full balance on them all. All the orings on the air needles and bleeders needed replacing. I found a plenum gasket that should be replaced. A worthwhile exercise.

 

So it looks like I have a 005 TPS. No idea if it came originally or if it is even a correct part.

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It looks like 005 is the correct part for F1 cars. I’m headed to a car meet, but can hopefully find some specs for this sensor later and test it out. The impedance values may still be exactly the same as the single connector versions, but I’ll want to check both sides. Not sure.

 

I didn't realise you had an F1 car. Let's hope you don't have to replace it the TPS. They are expensive and rare, including the aftermarket ones. I was looking at this yesterday for an hour or two. I think the cheapest was around U$300

I don't even have a (confirmed accurate) wiring diagram for one of those. I don't even know which plug goes to the ECU and which goes to the F1 TCU (or if it matters).

The picture on the left is the F1 TCU as per the manuals. However, the gated version was proven to be different from the manuals. The gated version on the right is correct.

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If you could gently pull back the rubber boots on the plugs and see if at least the wire colours match the pin numbers that would be very helpful. The wire colours in general should tell you which is the F1 plug and which is the Motronic ECU plug. Note that the pin numbering on the F1 TPS is 3-2-1 and 3-2-1 (not as shown).

In theory, the Motronics ECU TPS plug wiring on the F1 car should be the same as on the gated car (i.e. grey/white on 3, black/white on 2 and red/blue on 1)

The pale numbers next to the wires are the pin numbers on the ECU/TCU.

I've been told that on later cars, the wire which goes to the wiper arm on the potentiometer is shielded. I don't know if this will prevent you from identifying the wire colours.

 

The day has gotten away from me and I think I am too tired to work on things tonight. Hopefully I can get back to it tomorrow and start looking at this TPS. I did take the car out to see if I could floor it hard enough to get the valve to open. I tried to push the pedal through the floor, but no luck. Maybe I’ll catch a second wind in a couple hours.

 

Found a bit of a second wind, but it’s dark in the garage. I tightened the throttle cable, but that only resulted in less slack in the pedal. The throttle linkage appears unobstructed and hits the stops when it is floored. No change on the absolute throttle position % graph, other than I don’t have to press abnormally hard to reach ~75%. Tomorrow, I hope to find time to test the TPS impedance. Hopefully that can provide some good information.

 

I just checked the resistance value range on my TPS with the TPS fitted to the car and they were completely different from the values in the WSM. Either the throttle/throttle linkages are set up improperly not allowing the TPS to move through its complete range (by a significant margin).... or it's normal

Here are my values:
Pins:
1 - 2 : 1.991 k ohms (at all pedal positions). Values within tolerance.
2 - 3 : 1.062 k ohms (no throttle) and 1.915 k ohms (at full throttle). Values way out of tolerance
3 - 1 : 2.665 k ohms (no throttle) and 1.796 k ohms (at full throttle). Values way out of tolerance

These were on my original Bosch -004.

Here are the WSM values again.


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I fitted my new (spare) Bosch -001 and the results were somewhat similar, but the range was even less (by 46 ohms on the 2-3 pins). I may refit the old one.

I took voltage measurements on the TPS connector sockets with the ignition on (plug not connected), and found that both 1 and 3 pins have voltages on them.
pin 1 = 5.o volts (I think this is the normal voltage that the ECU sends to the TPS)
pin 3 = 5.8 volts (Is this a bias voltage as discussed earlier?). I couldn't backprobe the plugs to see what the voltages are with the plug connected. I would have damaged the plastic seals.

It was very fiddly and time consuming doing this. Be warned )))

I have a new engine harness on my car, and the TPS wire colours do seem to be different from the wiring diagrams. Hard to see in this photo, but the colours were:
pin 3: white/grey (not grey/white). Possibly TPS output signal wire. The important one.
pin 2: black (not black/white). Earth wire.
pin 1: red/blue. Possibly ECU normal supply voltage.

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My plug is black which makes it difficult to compare with your blue and white plugs.

Note that the TPS has additional fixed value resistances as well as the potentiometer.

 

The values given in the table above provided by Ian are the min and max values of the potentiometer, not the values at idle and full throttle positions. Here are the values of my new 0 280 122 004 at the stops of the potentiometer:

1 - 2 : 1.98 k (at all pot positions)
2 - 3 : 0.91 k (end position 1), 2.68 k (end position 2)
3 - 1 : 2.69 k (end position 1), 0.91 k (end position 2)

The pot has wider angular travel that the spindle of the TB so, when the pot is attached, the wiper will be a bit above the "end position 1" at idle position and it will not reach its "end position 2" at full throttle. The pot is designed in this way to avoid the risk of it being forced against its stops by the TB spindle.

 

We just have to figure out what is normal when fitted to the car.

Where is the "70+%" coming from on the OBD2 scanner? My highest 2-3 value is 1.915kohms. That's about 70% of 2.7k, but the graph begins at 1.062k ohms (idle) on my car, not zero ohms.

 

I am deep in the middle of building a raised bed garden for the wife, but I hope to find time to start testing the TPS at some point today. You guys are really going above and beyond to help solve this riddle.

On the F1 car, I wonder if the ECU takes the readings from both sides of the TPS into account when commanding the bypass valve open or just one side. It also sounds like the WSM values are only good to tell us if the TPS is good at min and max, but the actual values at idle and full throttle are more of a mystery. My graph does seem to show a fairly linear response as I go through the throttle range (no big dead spots or jumps that I have noticed, but will check again).

The main issue is I am never seeing over 75%, but we still don’t know for sure what that means on my scanner. It’s hard to know exactly what data the car is sending to the scanner and how the scanner is interpreting that data.

if anybody has an F1 car with a properly behaving bypass valve and a similar scanner (OBDLink MX+), I’d still love to see them test their absolute throttle position % to see if theirs goes above 75%.

Back to garden building for me and then hopefully I can get to testing the TPS later. Thanks again, everybody.

 

That's a big ask because the F355 F1 cannot talk to an inexpensive OBD2 scanner. It actually does not broadcast its data on the OBD CAN bus so ... unless the owner also owns a $40,000 Leonardo scanner, there is no way to read this data.

I have a 99 355F1 engine out in the garage (outside of the car) right now so I can do a few things if you know what you want to ask for.

 

The Motronic ECU only uses one side. The F1 TCU uses the other side. You just have to figure out which is which. I guess that will be easy if you have a scanner. If you remove one plug and turn on your OBD2 scanner, you won't see any changes when you push the accelerator. Or you could just pull the boots on the connectors to look at wire colours (take photos if possible.) The F1 plug should have a pink/black wire.

As you say, we may be heading in the wrong direction, but this kind of stuff will be really helpful in the future (and by doing these checks, you will be paying us back for our efforts).

 

Mitch, do you have the same plug colours on your TPS? (and are they in the same locations?)

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Yes,

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Good to know, thanks, Mitch. Your rubber boots don't look like they could handle a removal and install, so I won't ask

 

Do you know if the bypass valve was behaving correctly prior to the engine coming out? If so, let me first figure out which side of the TPS is sending information to the ECU using Qavion’s suggestion of testing with one side unplugged and reading with my scanner. Once I figure out which side we need the data from, if you can test resistance between pins 1-2, 1-3, and 2-3 at idle and WOT by manually moving the throttle linkage, that would at least give a baseline to see if mine is even in the same ballpark.

I’ve made a lot of progress on this raised bed garden (one of the conditions imposed by the wife that allowed me to buy the Ferrari) and it’s supposed to rain tomorrow, so good chance I’ll be able to get my hands dirty with the car tomorrow. If your resistance values are worlds apart from mine, that should give us a clue as to what’s going on. I don’t want to start throwing parts at the problem yet, but I’ll spend the money as soon as we verify that something seems off.

I’m still looking at possibly testing vacuum during a drive to rule that out as well, as you suggested that it shouldn’t be ruled out due to less vacuum being pulled above idle. The problem has to be either vacuum or electrical related, so it’s just a matter of narrowing it down bit by bit. To test vacuum, I think I can just attach a gauge to the output side of the reservoir and check for fluctuations while driving under different throttle positions. This car may force me into buying a cheap GoPro.

 

So here is the latest. The white connector appears to be the one sending data to the Motronic ECU. My scanner would not pick up TPS with that plug disconnected, but still would with the blue plug disconnected.

I did my best to gather resistance data from the pins by probing the pins (not easy due to its position) and having my wife floor the car after getting a solid reading at idle. Here is the data I got:

Pins tested: Idle - WOT
Pins 1-2: 2.05 - 2.05
Pins 1-3: 2.85 - 1.26
Pins 2-3: 1.19 - 2.55

Just at first glance, these don’t appear too out of whack except maybe the 2.85 and 2.55 values. I assume those should be the same value in a perfect world, but they aren’t off by a crazy amount.

Here are some photos of the process:


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IF we assume the values should be similar to m.stojanovic’s, I am getting around 76% of the range he is getting from idle to WOT on pins 2-3. This matches up pretty closely to what the scanner is showing.

 

If we take the gated car values and assume they should be the same for the F1 car, I am pretty far off from the lower resistance values.

WSM values again:

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My values again:

Pins 1-2: 2.05 - 2.05 (both within tolerance)
Pins 2-3: 1.19 (out of tolerance) - 2.55 (within tolerance)
Pins 1-3: 2.85 (within tolerance) - 1.26 (out of tolerance)

 

Best pictures I can get of the wires without messing with them too much to clean them up. I don’t want to disturb the old wiring to the point I cause more problems. Hope it helps.


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Zoomed in on the photos a bit for clarity. The resolution is reduced by the forum or image hosting site.

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@yelcab are you able to check the resistance on the white connector side of the TPS at idle and WOT to see if your values are similar to mine or if they match more closely to the values listed for a gated car? Hopefully it’s easier for you with the engine out.

I also want to double check my throttle linkage on the TPS-side cylinder bank. It sounds like it clicks on the stop on the left side, but it might be coming up slightly short on the right side. I’m close to pulling the trigger on a replacement TPS, but want a little more data before I do. Thanks.

 

Much appreciated. Thanks for trying. With a bit of imagination, it looks like your white plug (Motronic ECU) wiring is the same as my non-F1 car.

3: grey/white (output wire, low resistance to high resistance with throttle application)
2:black/white (earth)
1: red/blue (power?)

The F1 plug colours are still a little fuzzy.

One WSM F1 diagram, which has no pin number markings, shows:

black (definitely earth)
pink/black (power, I assume)
grey/white (definitely output wire)

Another WSM diagram shows:

3: black (definitely earth)
2: pink/black (possibly power as it supplies two different F1 sensors)
1: grey/white (output wire?)

Unfortunately, all of your blue (F1) plug wires looked striped.

From the wiring diagrams, the F1 half of the sensor is not wired up the same way as the Motronic ECU half. The earth and power wires are swapped. Can you confirm which pin goes to earth on your car with an ohmmeter (power off the car)? Maybe check the voltages on the other pins with the power on (TPS disconnected)?

Here are your values:

You seem to be getting a much higher resistance range than I am. I'm wondering if there is something wrong with my throttle bodies. Or perhaps the geometry on my RHD car is different. I have some extra linkages.

 

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Actually, that doesn't make sense. I have the same Motronics ECU as the USA cars. It would need to see the same TPS resistance values.

The range between your lowest and highest values on pins 2-3 is 1.36 k (mine is only around 0.85 k)
The range between your highest and lowest values on pins 1-3 is 1.59 k (mine is only around 0.87 k)

Weirdly, I get full pedal travel (fully up to carpet), but both of my TPS's new and old, give approximately the same ranges. How is the ECU compensating for this?

 

Motronic wiring definitely appears to be the same. Best I can tell, the F1 wiring is as follows:

Pin 1: grey/yellow
Pin 2: yellow/pink
Pin 3: green/black

I’ll try to see what pin goes to ground shortly. Looking back at this thread, I’m reminded I need to check the 14-pin connector near the Motronic ECU as well. Does this connector supply ground to a number of components or what is it I should specifically be looking for on this connector other than obvious corrosion/broken connections?