F355 OBD2 plug location

I have a UK right hand drive '97 355 with the Motronic 5.2 system. The question is, does anyone know where will I find the OBD2 plug? I see a black 3 pin plug (capped) located beside the engine ECU that is used for diagnostics, I guess. This obviously isn't a 16 pin OBD2 plug so what should I do?

I've also noticed a similar capped plug beside the ABS unit. Is this also a diagnostics plug? If so, does my car use individual diagnostics plugs for all controllers rather than a centralised 16 pin OBD2 compliant plug?

I've taken a look at the thread below and it seems that the 3 pin plug that I've found should be plugged into another 3 pin plug to complete its route to the OBD2 plug (if there is one).

http://www.ferrarichat.com/forum/showthread.php?t=55080&highlight=obd2+diagnostic+tester

Any help appreciated. Thanks.

 

If it had an OBD2 plug, it would be located under the dash, but only USA spec cars will have OBD2 plugs.

As you have discovered, Euro-spec cars only have the 3-pin connectors for use with the factory dianostic computers.

All of the other systems (ABS, Climate control, etc) have their own 3-pin connectors for diagnostic purposes, even on the OBD2 compliant versions. Only the Motronic control unit is connected to the OBD2 connector.

 

Thanks for your help, motob. Do you reckon the 5.2 control unit is OBD2 compliant regardless of US/UK spec and if so would connecting the 3 pins at the engine ECU diagnostic plug to the relevant pins on a generic OBD2 tester work?

 

It has been my experience that even the US OBD2 plugs do not work with generic diagnostic testers. I believe Ferrari has switched the positive and negative pins?

 

your OBD2 plug is located to the right of the steering wheel tucked up under the dash- 99 percent sure- if not the right , the left. but deff next to the steering wheel.

 

Not true, all US car's will work with a generic tester for OBD2,I have a tester that we use for all cars, and use it on Ferrari's for check engine lights etc when the ST5 is in use. I have worked of left hand drive Euro cars and the OBD connector is in the same location as a US car, up under the dash on the drivers side to the right of the steering coloum. I dont see why a right hand drive would be any different.

 

Found this thread. Post 56 onward discusses the OBD2/EOBD interface on the 5.2 F355

http://www.ferrarichat.com/forum/showthread.php?t=121381&page=3&highlight=hesitation+acceleration


These people can provide an OBD2/EOBD interface here in the UK.

http://www.ukobd.co.uk/gstore/store/g_viewItem.asp?IDproduct=41


I'll give this a try and post results.

 

What type of tester do you have? I had all the different tool reps in and none of their products were able to read codes?

 

I too would be very interested to know of a tester that works on the 355. I've tried a few on approval, big makes as well, that have all failed spectacularly to communicate using the o.b.d plug. Does you tester work on the 360's o.b.d too, and if so, can you look at stuff like variator readings? I'd like to buy myself a tester, as the SD3 porting software is utterly crap, and doesn't do things like the 355 capote cycle test. Many other diagnostic functions are limited on it, and with a rapidly failing SD1, and no SD2, i'm getting desperate!!!!

 

We have several testers, the generic one i use is made buy Autoboss USA, cost about $4 grand, it will do all functions on Mercedes,BMW,Audi,VW,Mini, and all OBD functions on all cars.
The Ferrari tester we use is called an ST5 it is made buy the same engineers who make the SD3, but you dont need a licence key, it will do 355,360,550,575,F40,F50, and I am waiting for the 430/612 software. It is a little slow, and has had a few glitches, but they have been rectified with new software. It will also do Lambo and Masserati, but i wount work on those so cannot tell you how it functions. Cost is about 20k. PM me if any one wants details on getting either system.

 

Ferrari-Tech, Sounds like you have some pretty fancy and pricy equipment. Good for you. I still think Ferrari makes things more than they are supposed to be. I believe the spirit of the US law states that basic OBD2 faults are supposed to be accessable by just about any service department with some simple hand held diagnostic tools.

 

You are correct. Federal law states all emission/check enging light codes must be accessable to any smog center. These are normally codes that start with a PO #, and are generic to all cars. I.E a PO455 indicates a major leak in the evap or purge system. Now some manufacturer's go above and beyond what is required buy law, for instance Mercedes have over 2000 codes, of which i think only 100 or so are federally mandated. Most other makes only do the bear minimum. So if some one with a Merc tells you there check engine light is always coming on, its because if they are supposed to check system XX with a one wire sensor now, but in two years the regs change to two sensors and 2 wires, Mercedes put on five sensors and 20 wires now because they can, and they are always over self testing.
I have seen Ferrari's with faults that would put a Merc or Porsche in limp home mode, not even have a CEL.
As for our shop equipment, thanks for the compliment, but I think it is a wise investment to have the latest diagnosistic machines, it's not fair to our clients to do otherwise
Anyone in the area is free to come buy and use any of our machines ( with supervision of course) to aid in any diagnosis or repair they want to do on there own cars, again PM me if we can be of anyhelp

 

Sorry if this has been covered before, but there is currently an open recall on all 1996 to 2002(?) Ferraris to correct the ground pin on the OBDII connector in USA cars. The problem is that Ferrari appeared to intentionally wire the plug (by omitting one ground wire) so that it required one to use Ferrari's proprietary SD2 or SD3 in order to read the fault codes. This was in violation of EPA standards, and hence the current recall. If you have the recall work performed, then you indeed can read the fault codes with any common OBDII reader.

See attachment for a copy of the recall.
View attachment obd2.pdf

 

Good news! I've managed to borrow an "Autoxray Ezlink" (www.autoxray.com) OBD2 fault code reader from a colleague in the motor trade. It worked first time with no problems.

It seems that the euro cars (like mine) DO NOT have a OBD plug but just the Ferrari specific plug that's located beside the engine ECU, so a connection will have to be made at this plug to use a generic tester on a euro car (see below). The US cars WILL have the OBD plug, so this tester should work OK and if it doesn't it may be worth checking that Ferrari have used the correct OBD plug pins.

Take the Ferrari diagnostic plug (3 pin plug by the engine ECU) and, holding it facing you with the retaining clip uppermost, the connection should be as follows-

Left pin to OBD plug pin number 15 (L line)
Middle pin to OBD plug pin number 5 (signal ground)
Right pin to OBD plug pin number 7 (K line)

This tester managed to identify the correct protocol first time, read trouble codes and feed live data (oxygen sensor, RPM, coolant temp etc) with no problem.

It seems strange that this tester worked OK and yet so many others seem to have "problems". I reckon that the problem lies with the incorrect pins used by Ferrari at the OBD plug and not the tester that is used.

Anyway, the code reader live data reading said that my car was only getting 77% throttle and yet the cable is fully stretched. A labscope test indicates a smooth progression at the throttle potentiometer to about 4.5 volts. Does anybody know how close to 5 volts the voltage should be at 100% throttle?

 

I don't know the volts, but the workshop manual gives the specs in ohms. You could remove the throttle potentiometer and test that it is reading the correct ohms at each extreme. (it is a bear to get the clips on there with the throttle potentiometer in place)

 

I was working on an idle instability problem on my 355, and "91TR" (SteveM) was able to assist me with some help using my copy of the WSM, and gave me these instructions for testing the throttle potentiometer per the factory specs:

"With the throttle potentiometer unplugged (note the little tiny 3-2-1 letters on the connector body to identify the terminal pins):



1. Measure the resistance from terminal pin 1 to terminal pin 2. These two terminal pins are connected to the ends of the stationary thick film resistor. The resistance will remain the same regardless of the throttle position and should be 2000 Ohms +/- 400 Ohms.



2. Measure the resistance from terminal pin 2 to terminal pin 3. When at the "MIN" position (which I guess means at the idle position), the movable sliding contact connected to terminal pin 3 is at its closest physical position to the fixed end of the thick film resistor connected to terminal pin 2. Consequently, the resistance will be at its minimum value and should be 850 Ohms +/- 153 Ohms. As you open the throttle, the moveable sliding contact attached to pin 3 moves away from the fixed end of the thick film resistor connected to terminal pin 2 which causes the resistance to increase. The resistance should increase in a smooth linear manner as the throttle is opened and in the "MAX" position (which I guess means WOT) the resistance should be 2700 Ohms +/- 540 Ohms.



3. Measure the resistance from terminal pin 3 to terminal pin 1. When at the "MIN" position (which I guess means at the idle position), the movable slider connected to terminal pin 3 is at its farthest physical position from the fixed end of the thick film resistor connected to terminal pin 1. Consequently, the resistance will be at its maximum value and should be 2700 Ohms +/- 540 Ohms. As you open the throttle, the moveable slider attached to pin 3 moves towards the fixed end of the thick film resistor connected to terminal pin 1 which causes the resistance to decrease. The resistance should decrease in a smooth linear manner as the throttle is opened, and in the "MAX" position (which I guess means WOT) the resistance should be 850 Ohms +/- 153 Ohms.



You may meet these specs just fine in a one-time measurement, but what you should really be looking for is an instability in the 2-3 or 3-1 resistance at the idle position from the wear and/or debris. For example, measure the 2-3 resistance at the MIN (idle) position and note the value. Then slightly open the throttle and confirm the resistance goes up a tad. Release the throttle back to the idle position and confirm the resistance drops back down to the previous value. Do this like 10 or 20 times. If the resistance ever jumps up to a much larger value during this slight moving back and forth motion that would be a sign that the sliding contact connected to pin 3 is not always making consistent contact with the thick film resistor at the idle position.



Another way to measure how this gizmo is working in a functional manner (i.e., with everything plugged in and running) would be to measure the voltage on the wire connected to pin 3 relative to a good ground (like the engine block or cylinder head). The voltage on the wire from pin 3 (the moveable sliding contact) should always be about the same at start-up idle. Like they note, this can vary a little -- and the ECU "learns" this value at each restart -- but, if it's ever way, way different than normal, that would also indicate that the moveable sliding contact is not making good contact with the stationary thick film resistor."




Note that when I tested mine, it was within spec, but near the max tolerance in some values. I could never fully confirm, but appeared to have intermittent operation once in a while.. I think all my fiddling with mine, may have cleaned up the contacts and it's operation. Since I found new Bosch throttle potentiometers online for only $87.16 including shipping, I decided to go ahead and replace it. The new one was much closer in spec than my old one, and so far, I have had no further idle issues (a rare, intermittent, low idle upon start up, either cold or hot).

 

Thanks for all that info', that's a great help. I'll check the potentiometer resistances when I've got some more spare time.

The reason I started to check fault codes, live data etc is due to two problems-
1 The engine started surging very slightly at steady speed when hot.
2 The engine hesitates and sometimes pops back on sharp throttle openings off idle (OK at anything above idle). This happens hot or cold.

I suspected a fuelling problem causing the surging when the engine is hot and the ECU goes closed loop. I didn't have a code reader, so checked the upstream oxygen sensor outputs using an oscolloscope. The result was that both upstream sensors were flatlined at about 150mv - not good. I replaced the sensors (Bosch original part complete with original type multiplug for £65 each). The surging dissapeared.

I've now got live readings from the upstream sensors with the code reader and they're both good. They switch regularly from about 100mv to 900mv.

The hesitation/pop back remains. So, that's when I started to suspect the potentiometer.

I've also checked the air mass output both with a scope and the code reader. The scope shows a steady 1 volt at idle with progression to 4.5 volt at full throttle. However, when the hesitation occurs the reading spikes up to 4 volts or so rather than progressing smoothly. I'm not sure if this is the air mass meter misbehaving or the induction backfire causing the spike in the air flow. Perhaps the 1 volt at idle is too low and subsequently the engine is lean enough to cause the induction pop on progression? Or is an injector partially blocked and causing a cylinder to run lean (although all the plugs looked the same)?

Just for good measure I've also looked at the plugs and leads. The plugs are all good (about 1K miles old) and look as I would expect. The leads were, if I remember right, about 5-7K ohms each with one that was noticeably toward the higher end of this scale.

Incidently, used the code reader on an EOBD car today (Peugeot) and that reads 78% at max throttle opening. I'm suspecting a software issue with the code reader now.

 

If the throttle pontentiometer reads o.k i would begin to look down a different route. You may have a small vacuum leak, especially if the idle is erratic when hot( out of open loop) and would be tempted to do a bank-to-bank comparison of manifold vacuum using a hand held guage. It may have a small leak in one of the pipes or joints in the engine valley, which is large enough to cause an idle issue, but too small to flag an engine warning lamp.