97 F355 Spider ECU Issue/Smog Issue

The answer of your car is the same than mine.
The useful data is #BF 9F F9 90 . It describes which PIDs (parameters) are accessible on this car out of the OBD2 generic list. It decodes as the table below. Only the non-greyed paremters are available with a generic OBD reader. All the other ones require the use of a proprietary reader (SD1, SD2, ...)
Sorry, it doesn't really help with your problem but I was curious to see why the S/W was able to decode some Fuel Trim on Bank 3 and 4. Probably some wrong or misinterpreted labels.
Each PID can be read manually by the command 01xx where xx is the hex number of the required PID (eg 010C for actual RMP, 0103 for the "open loop/ closed loop" status), the interface will return the hex value of the parameter which can be converted to physical value according to the last column of the table.
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OK, let me know if he check your ECU with a Ferrari diagnostic equipment and if it finaly solves your problem.

The electrical diagram you are looking for is in the WSM volume 3, page H62. Thanks to Ricambi America you can consult it online: http://www.ricambiamerica.com/wsm/355vol3/355WSM_3index.htm (page 64).

 

I think it must be almost impossible to find the electrical diagram of such an ECU.
From what I have seen, the two relays are double-relays which are most probably driven by the group of 4 TO92 transistors at the bottom left corner of the PCB. Have you checked the 4 coils, the 4 transistors and the components around (free-wheeling diodes, ...)? I don't think the microcontroler can have failed on only 1 output. From what I read, the potentiometer seems OK. Have you checked that the voltage it sends back to the ECU is consistent with the seat position?
An idea if you don't find the failure and don't want neither to put $2000 on another ECU: you can try to copy the movement of the passenger seat onto the one of the driver seat (ie to command both the passenger seat relay and the driver seat relay at the same time, and to duplicate the driver seat potentiometer). It may works if you take care to have both seats in almost the same starting position ... or you can add a manual switch which commands directly the relay of the passenger seat to ensure the backward movement.

 

Tom,
On top of the possible Motronic ECU issue, what could be causing the other reading problems? Bad sensor connectors or wiring harness?

 

Two things I would do for the above items:

1) Make sure you have a ground strap from the alternator to the oil sump. This was a update performed by Ferrari. You can buy the part from Ricambi America, or make your own for $2 with some 10ga wire and terminals.

http://www.ricambiamerica.com/product_info.php?products_id=208383

2) For the fan motor thing, you need to replace the fan motor assembly. As they age, they draw excessive current, which makes the alternator work very hard, causing the idle drop...and given a few seconds, the engine will recover.
Fortunately, a less expensive source for the fan motors was found. See this thread:

http://www.ferrarichat.com/forum/showthread.php?t=194555&highlight=355+fans


See this also: http://www.ferrarichat.com/forum/showpost.php?p=137693408&postcount=48

I would recommend replacing both fans.

 

In your previous post, phases A, C and E are correct. With no sensor or cold sensors the Motronic return a 0.43V value. I have the same on my car, this is due to the polarisation stages in the Motronic. Obviously phases B and D are very strange and I cannot see any good reason to have 0V on these inputs but a short circuit on the sensors wires or a very very lean mixture (I have 0V only during costing phases when no fuel is delivered).
Improving the grounding of the sensor has no effect IMO because none of the wires in the sensors are connected to the ground.

To investigate these inputs, without the engine running to avoid exhaust gas effects on the sensors, I would suggest the following:
connect a 1.5V battery to a potentiometer (1 or 2.2 kohm), then connect the minus pole of the battery and the cursor of the potentiometer in place of each sensor. You will then be able to generate a variable voltage and check the consistency of the OBD data...

... but a similar problem on 2 ECU is probably due to an external cause: harness, connectors (have a look inside the Motronic connector), Motronic grounding, ...

 

My compliments to Eric355 for sharing his knowledge.


Jay

 

Good catch...what part numbers were you using? Were these Bosch O2 sensors?

 

Interesting. I thought the only difference between the pre and post cat O2 sensors was the length of the cables. That their electrical operation was the same, as they are both four wire sensors with heaters.

 

Where did you get your numbers?

I have been using the following Bosch part numbers for Motronic 5.2 F355 (1996-1999):

Pre cat #13819 ($128 plus shipping from www.rockauto.com)
The full part number is 0258003819

Post cat #13820 ($128 plus shipping from www.rockauto.com)

I needed a pre-cat O2 sensor once late on a Friday, and simply bought a Bosch, four wire "universal" from the local auto parts store (as recommended by Bosch on their 800 customer service #), ditched the provided "splicing block" and soldered my old plug onto the new sensor, then used heat shrink tubing over all four solder joints, and one big piece over all four joints.

Okay, checked on the Bosch "universal" O2 sensors, from the www.rockauto.com website:

Pre cat is #15730 ($50 from rockauto.com)

Post cat is #15738 ($81 from rockauto.com)

The universal ones will require either splicing or soldering the old plug onto the new O2 sensor. Must be some difference between the two sensors, just based on the big price difference between the two. Strange there is no price differential when you buy the "plug and play" versions that come with the factory plug.

Tom, I just looked online at the 15727, and it sure looks like it should work fine (rockauto even crosses that one over to the 96 to 99 F355), it has the correct threading and four wires. I asked the tech guy at Bosch when I did mine, and he told me that all of their O2 sensors where essentially the same, the primary differences were how many wires (1,2,3 or 4), the threading on the sensor, the length of the cable, and the plug type on the end. So he said any number of their "universal" kits should work, as long as it is a four wire, with the correct threading. All one had to do was correctly splice the plug on. So that begs the question.....how did you do the splice? You might want to check that, and perhaps redo it, solding the wires. I really didn't like the look of the splicing block Bosch provides in the kit.

BTW, it is "possible" the 15727 is not correct. I will tell you that Bosch's own look up guide is all screwed up, and mixes the part numbers all up between the 94-95 2.7 motronic, with the 96-99 5.2 motronic. O2 sensors are listed and mixed between the two. I have always found it more accurate to use the online look ups, and enter a "1999" F355 as that will usually get you the correct parts. Often times, if you look up under a 1997 Bosch will list the 2.7 parts...but you can catch it when the list TWO fuel pumps, or TWO MAF's or TWO idle control motors...since ours has only one...and completely different part numbers than on the 2.7 cars.