What's new
By:
Club Scuderia

This is a sample guest message. Register a free account today to become a member! Once signed in, you'll be able to participate on this site by adding your own topics and posts, as well as connect with other members through your own private inbox!

  • Please take a minute to read this thread about our recent server issues and forum platform Switch

Ferrari 355 M5.2 open loop fault on bank 1 only

R

redwedge

Member
Hello, anyone have any idea what might be going on with my 355? It failed its MoT on emissions, with the lambda reading being too high. I drove the car home and had a quick look using my OBD2 reader. The front O2 sensor readings didn't look right. Bank 1 was stuck at 0.435V. The other was oscillating reasonably nicely. With no record of the O2 sensors ever being changed, and both likely being 27 years old, I changed them both for brand new Bosch parts. Not much change on bank 2, which was already working correctly anyway, albeit with a large negative LTFT. SHRTFT looks much better on that bank now, so hopefully the new O2 sensor is the fix for that issue.

However, bank 1 is now constantly reading rich at 0.8V, with the ECU refusing to take any notice of it and displaying "OL-Fault" on my code reader. I don't understand how bank 2 can be closed loop but bank 1 not, as they share all sensors except O2, as I understand it.

Anyone seen this before, or have any idea how this situation of being OL on one bank and CL on the other can arise?
 
Just thought I'd come back to say that the fix for this was for the lads at KHPC to reset some ECU parameter in SD1. I had done a battery cutoff reset but apparently not sufficient when fitting new O2 sensors.
 
redwedge said:
Just thought I'd come back to say that the fix for this was for the lads at KHPC to reset some ECU parameter in SD1. I had done a battery cutoff reset but apparently not sufficient when fitting new O2 sensors.
Click to expand...

Thanks for the update
redwedge said:
I don't understand how bank 2 can be closed loop but bank 1 not, as they share all sensors except O2, as I understand it.
Click to expand...

Battery resets don't reset fuel trims on 5.2 cars, so I guess the LTFT was still too far out of tolerance to allow closed loop operation. I wonder if it would have come back into tolerance if you kept the engine running a little longer?
 
Back
Top