Keep getting code 4123

I'm not an expert, but it sounds like you could have a bad thermocouple or cat ECU maybe?

 

Are you sure on the code? I have not seen that one listed on the F360 codes list, which both cars appear to share. Assuming that is right, it is likely the cat ECU that is acting up on the 5-8 side. What year is your car/Motronic version? All F355's came with cat ECU's sealed with black epoxy, and it will crack and allow moisture in and fail. Call Daniel at Ricambi America, order a replacement in the new style with green epoxy (the only style available from Ferrari anymore) and swap it out and you should be good to go.

To confirm the problem swap cat ECU's between the left and right sides, before buying a new one. If the problem doesn't move to the other side, try swapping the thermocouples instead, and see if that moves the problem.

 

Try this .... from engine cold, unplug the battery for 10 minutes and then after plugged back, run the engine on idle until the cooling fans start up. During the entire procedure, radio, lights and internal fan must be off and .... don't tap the throttle either. This procedure resets the ECU's and re-program them from cold to hot. Try, what you got to lose ?

 

I have a 95 F355 and my 5-8 light keeped coming on. It was the air flow sensor that is located between the air box and the inlet manifold. The 95 355 has two of these. One for each bank. To test these you can swap them over and then see if the other bank warning light comes up. If it does, there is the problem. Good luck.

 

Were you getting a "check engine" light as well, and if so, what was the code?

 

Unlikely.

 

I'm confused, in your first post you said you were getting a code 4123, is this not correct?

You are not ready to buy a mass air flow sensor, since you have not yet diagnosed the true problem. Both myself, and J0W02 have given you diagnostic methods to rule out either the cat ECU and the MAF respectively. Please try those first, before buying anything.

 

If it is the air flow sensor then all we did is give it a good clean. The problem with mine was it was dirty. I believe there is a wire probe inside the heats up and when the air flows through it cools the wire given a reading of how much air is passing it. It then does some calculations combining the data with your O2 sensors to make sure everything is OK. If it doesnt read properly then it can shut down one bank to avoid damage and the warning light comes on. I have a friend who had the warning light also come on. His problem was that the sealant they use to seal the cables that go into the air flow sensor had dried out and cracked. If water get in then it can cause this problem also. As mentioned, firstly you have to eleminate that these sensors are OK by swapping them. From what I can remember we didnt even remove them. We unplugged the cables and simply plugged them into the opoosite ones as the cables reached. These are very expensive, arround $1200. I have seen some S/H ones on Ebay in the UK recently for a fraction of this.

 

The MAF should have a Bosch part number. IF it is bad, you can search the part number online, if it is used on other cars, it will be relatively inexpensive to purchase, versus through the Ferrari parts network. That is the case on the MAF for the 5.2 Motronic. It is the same unit used on the 4.0 liter BMW V8 E34 and available online from dozens of European parts houses.

Most of the Ebay MAF's are made in China or eastern Europe if they don't explicitly say "Bosch"...but rather are described as "aftermarket". Avoid them like the plague. On the BMW and VW forums, people have been suckered into buying them and they don't work...you will have even worse running problems.

Please, don't get ahead of yourself. We don't even know if the MAF is bad, and it may be able to be cleaned with some electrical contact cleaner or dedicated MAF spray cleaner.
Run the diagnostics, and let us know what you find.

 

Found these new MAF on Ebay but only states 96-. You will need to check they are suitable.

http://cgi.ebay.com.au/MASS-AIR-FLOW-SENSOR-METER-FERRARI-F355-GT-1996-1997_W0QQitemZ400113256984QQcmdZViewItemQQptZMotors_Car_Truck_Parts_Accessories?hash=item5d289bca18

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These sensors are made by Bosch and are also used on BMW's and other cars.

Bosch Part Number: 0280217800

FERRARI F355 Spider (10.1995-03.2009) F129C/40 3.5 280Kw

This sensor is fitted with the correct connector to plug straight into the standard genuine connector on the vehicle listed above.

 

Those are the CRAP I am talking about, they are NOT made by Bosch...and those are for the 5.2 Motronic anyway and will not fit.

See this quote from the Ebay listing:

"Manufacturer: AIP Electronics"

 

No, you will need to physically move the left ECU, and swap it with the right. See if the problem moves to a "check engine 1-4" light. If it does, then you need to replace the 1-4 bank catalyst ECU. If it does not move, then try swapping sides with the thermocouples.

I really think you should have started with the cat ECU swap, as they are a commonly troublesome part. Although moving the MAF is definitely a lot easier, and less messy.

 

Why don't you try swapping the cat ECUs as "Hugh" here recommended???

 

Clean the grounds at the rear of the car...

 

I am unfamiliar with 2.7 Motronic codes, but if it is similar to the 348 codes, it would be for the speedometer...but a speedometer problem should be readily apparent. I would stay focused on the 5/8 light and get that resolved first. When you retrieved this code, did you have the "check engine" light illuminated? Or was this a stored "pending" code? (does OBDI allow that?)