Check Engine light 5-8

Time to check your trouble codes by pressing the button next to the (US) driver side ECU and waiting for the CEL to flash a code. That should point you in the right direction. The codes should be stored even though the light is off.

 

No always - just had the same issue this week and no codes. A good friend experienced this in his 95 and suggested it's likely and O2 sensor. At $50.00, pretty easy test and I have one on hand so will try myself this week.

Oh, and if you don't already know, when pulling codes you will get an 1121 (PRM sensor) as the motor is not running so no RPM is being sensed.

 

5-8 is bank 2, on LH side.

See attached
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If you find a code I bet it's a 1114, 1211, or 1212. If so, my experience indicates most like cause is an old O2 sensor. But with OBD I if it senses a problem it turns on the CEL. If the does not reoccur within a certain time it turns it off. Depending on how long the CEL was lit it may or may not set the code. But, if the CEL goes off it means the error resolved itself. I don't usually recommend replacing parts w/o proper diagnoses but at $60 at Rock Auto, replacing the O2 sensor is a cheap diagnostic tool if you have one of the above codes.

1212 and 1211 can also mean a problem with the signal from the MAF, i.e. clean contacts at connector, or a vacuum or exhaust leak.

 

Please report back what you find.

 

As said before, you most likely have a failed o2 sensor. First thing I'd do is switch it with the right hand o2 sensor and go for a drive. See if the CEL switches to the 1-4 side. If it does, replace that sensor. If not, start checking through other things like wiring and MAF sensors.

 

If you live in the USA I would not switch it. For $60 from Rock Auto, I'd just put in a new one and see how it goes. Worth the $60 not to have to mess with the other side.

To change you have to removed the engine bay side shield, remove 3 nut that hold the clips that hold the wire in place, unplug the connector, then get to the sensor with can be a real pain, especially if you don't have one of these.

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Very straight forward job. As John said , get a new one rather than swapping them.

The wrench John showed makes it easier but may not be necessary. Make sure you put anti seize on the new threads and hopefully the guy before you used it on the old one.

I had one that was "welded" to the cat on account of no anti sieze. No fun even with the cat removed and in a vise.

 

As mentioned, you have a diagnostic code readily available...pull it & read it. why guess?

My lit LED ('95 spyder) was due to the diverter valve being tied open.

+1. No swapping sensors or ECUs or anything. If the code points to the sensor, just replace it. If you want, there is a test you can do on the sensor. It's in a thread here somewhere. Put an ohm meter on it & heat it with a propane torch and check the ohms. Then chuck it 'cause you've already put a new one on. BTW: mine tested fine this way and I still chucked it as I replaced it for < $30

 

New Bosch sensors come primed with anti seize.

 

Now here is one of several reasons why an F355 Challenge is so much fun. My 1995 always throws check engine lights for both banks. Prior to its major service two years ago, it was the Check Engine 5-8 light that would come on when the car was idling or moving slowly. It went off when I picked up speed, The light for the 1-4 bank came on occasionally and behaved like the 5-8 bank light. After the major service, both lights come on within five seconds of each other and go off the same way when I pick up speed.

I guess my engine is properly balanced.

 

https://www.rockauto.com/

 

I've had a few seized ones as well, Bob. So much for the effectiveness of "factory applied" anti-seize....

 

Ferrari, 1995, 355 B or GTS (spider not listed, makes no difference, chose either), 3.5L V8, emissions, Oxygen (O2) sensor.

https://www.rockauto.com/en/catalog/ferrari,1995,f355+berlinetta,3.5l+v8,1103971,emission,oxygen+(o2)+sensor,5132

Give the link time to load.

Oh my, Price when up to $70.

 

On the front end of the catalytic converter.

 

Item 34.
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