2014 MPI fault codes 321 & 322

[stang32]

hi all, i wrote about this issue last year and after tuning the engine, the customer was pleased to inform me it never ran better, then a week later he called saying the DTC light was on again.

i have this boat that is throwing 2 hard codes, 321 starboard cylinder bank fuel trim too rich & 322 , starboard cylinder bank fuel trim too lean .I've erased them and they come back within and hours time running. the boat goes into closed loop and the sensors are dancing but i can't find info on what their perameters should be and i can't find much info on line about this issue and wondering if i can get some help.
without me being on the boat monitoring it until the light comes on, i am stumped. i can see if the code sets for too lean and tries to richen the mix then it goes too rich but why would it richen it soo much that it throws a code? i put new O2 sensors in it less than 20hrs running time ago.

serial # 2a191194​

 

[Searay205]

I had 321 after the boat sat all winter. Never came back. Make sure you clear the trouble codes and history or the codes will come back. So go into history and it will tell you exactly when the alarm hit and what all the parameters were, you need to clear that also.

To rich sounds like injector is leaking but again mine was a ghost code when I get home I will look in my manual.

 

[Searay205]

Sorry manual all but useless. My suggestion buy PCM 555 and associated wiring harness. If an O2 sensor is weak or bad it will cause the codes to throw.

 

[nola mike]

Lazy o2 sensor could do that, not reacting quickly enough. Can you post the values at the time of the fault? Does your reader allow you to look at how quickly o2 sensor cycles, and min/Max voltages?

 

[Searay205]

I was thinking the same as nola mike. its failing both ways, lean and rich, common denominator is o2 sensor. O2 sensors cheap, either swap sides or buy a new one. Did someone flush the engine or throttle body and contaminate the sensor?

 

[stang32]

well, this engine is a catalytic converter engine, 4 sensors, all a pain in the ass to get to, shields and such. the sensor were not cheap, customer wanted OEM and thats what he got. the 02's are new and i am hard to believe that they are bad already. and just an FYI. this is a lake boat.

 

[nola mike]

well, this engine is a catalytic converter engine, 4 sensors, all a pain in the ass to get to, shields and such. the sensor were not cheap, customer wanted OEM and thats what he got. the 02's are new and i am hard to believe that they are bad already. and just an FYI. this is a lake boat.

What's your theory?

 

[Searay205]

The rear o2 sensors will only last a year or two. The front sensors should last a long long long time. The reason the rear sensors fail is they rot. I have all new manifolds but disconnected the rear sensors since they didn't work (rotted out). Use a o2 simulator to eliminate alarm. I removed my O2 sensors to install plugs (cleaner look) and was shocked when I removed them they were soaking wet!!!! The boat hadn't been used in 3 weeks and stored in enclosed storage!! Even though the o2 sensors are in the gas passage of the exhaust elbow, they still get soaking wet and stay that way and rot out at $100? plus each.