I’ve asked on a group messenger too, but just incase anyone here can assist. my 96 5.2 is intermittently dropping a bank/limp mode when 15/20 minutes into a journey, it will resolve itself until the next time. I have no lights on the dash although they’ve been removed by a Previous owner, I’ve had the car 5 years and done 15,000 miles in that time so no concern there. I’ve code read the car, cleared the codes and then checked to see what codes re appeared, which are as follows P1447 P1691 P0140 P1117 P1121 P1454 P1449 P1448 P1452 P1445 P0102 what doesn’t help is the fact the issue/dropped bank comes back online relatively quickly, so it’s difficult to know which bank it is. the car had its major 3 years ago and new coil packs were fitted at this service. I’ve recently replaced the following to try to rectify this issue spark plugs HT leads Fuel filter New battery and leads I replaced the plugs and leads as water had found its way into some and were arcing, could this have damaged a coil? is there any codes which stand out which could be causing this. I’ve never replaced any relays, sensors, MAF or fuel pumps during my ownership, if there’s certain relays etc I should be paying close attention to then I’m all ears!
We don't have a decoder for the F355, but use the Ferrari 360 one instead (there may be differences). P1447 N/A F355 P1691 N/A F355 P0140 02 Sensor Circuit (Downstream Catalyst) (Bank 1, Sensor 2)... no signal P1117 02 Sensor Heater Circuit (Downstream Cat.) (Bank 1, Sensor 2)... short to ground P1121 02 Sensor Heater Circuit (Downstream Cat) (Bank 2, Sensor 2)... short to ground P1454 Catalyst Protection Active (Bank 2) P1449 Catalyst Temperature (Vescovini) (Bank 2) ... out of range.. Right (?) bank P1448 Catalyst Bypass Flap Circuit ... malfunction... signal miniumum or maximum P1452 Secondary Air Pump Circuit... open circuit P1445 Catalyst Temperature (Vescovini).... range/performance P0102 Mass Air Flow Circuit (HFM) ....low input. O2 sensor heater circuits are wired differently on the 360, but an intermittent short to ground won't help. There is a single fuse for all the heaters, but if the fuse was blown, it wouldn't recover. Maybe look for signs of stress on the fuse (burning). Passenger footwell, fuse 22. Fuse 22 is supplied with power from relay N, the fuel pump fuse. If there was abnormal current momentarily going to the O2 heater circuit it might affect the fuel pump. Or vice versa. Might be a fuel pump issue. Catalyst protection active might also cause the left bank to shut down. Could be a high exhaust temperatures or a faulty thermocouple ECU. If it happens again, see if either of the cats are glowing? P1452 Secondary Air Pump Circuit... open circuit. The 360 is different from the 355 with regards to this message, but it might mean the secondary air relay coil has failed or there is open circuit wiring between the relay and the Motronic ECU. Easily checked, but it may not have anything to do with your bank loss. Mass Air Flow Circuit (HFM) ....low input. Water has been known to get into the MAF connector. Disconnect, clean and refit. Whether this might cause a fuel/air ratio issue leading to high cat temperatures, I don't know. Now over to the real experts.....
Thanks I’ll check some fuses and clean the MAF first regarding the left bank cat thermocouple ECU, firstly is that this? secondly can I swap this over to the right bank to see if the codes 1454 and 1449 change to the codes relating to the other bank?
Yes, standard troubleshooting is to swap the parts side to side. You can swap the temp sensor first and see if the problem jumps, then it's the actual sensor. If it doesn't jump, swap the ECU side to side and see if it jumps, in which case that's the issue. If it doesn't jump, then it's likely an intermittent wiring issue. Funnily enough, after a few years of not doing it, mine started doing the same over this past weekend. I had one bank drop issue, came right back and hasn't done it again, but I've seen a few slow down lights that almost immediately shut off. In all cases it was after the car had been shut off and then turned back on a while later and driven, both happened before the cats would have had much time to get hot enough to be an issue and then went away for the rest of the drive. That tells me it's probably the temp sensor itself having a fault at a certain temp, but uncertain. If it continues to do it, I'll have to do further troubleshooting.
so the side relating to the cats which have flagged up on the codes just so happens to be the easiest ecu to access, can i not just unplug the ecu and drive the car to see if this stops the car dropping the bank? I recall people running their cars with these unplugged, my old 348 came to me with these already unplugged, not sure if the same can be done on the 355
Seems to me the first step is figuring out which bank it is. A cheap laser thermometer should do that very quickly. The exhaust manifolds on the two banks should be very different temperatures.
well I thought the codes pointed towards the left bank, Number 2 I can get an infrared thermometer here tomorrow, but don’t forget the bank comes back online on its own, so it’s not one bank continuously down, would you still expect a difference in the temperate of the two manifolds? I have just installed some bulbs in the instrument cluster, I have the slow down light blinking straight away
You get a Check Engine light on the F355 if you do this. If the fault swaps, Technistrada offer a cheaper and more reliable version.
If you unplug the thermocouple from the Exhaust ECU (the 2-pin connector), it will cause bank shut-down. One possibility is that either you have poor (intermittent) connection of the Thermocouple to the Exh. ECU or the Thermocouple is on the way out. As Ian informed, you will get a CEL if you unplug the Exh. ECU from the harness. I do not know whether this will also cause bank shut-down; Ian?
Not sure. The Motronic ECU does know if you've accidentally plugged the bypass ECU into the RH Cat ECU. That gives a CEL, but no shutdown.
Eleven CEL codes. You are second to Ketel's 13 CEL codes that took ... ahem... 3 years to sort out. These codes are telling me that you are having issues with Bank 2. I would suggest you focus on the Thermal Control Unit on bank 2 and solve that before you head down any other path. 1. Just flat out change the expensive TCU. Clear the codes and drive. 2. Or swap left to right TCU to see if it shows up on bank 1. Then change the offending unit. If it turns out that your Bank 2 TCU is fine, then you have to focus next on why the TCU is seeing that high temperature while running. Use a laser thermometer to see what temperature your bank 2 cat converter is at. If you drive it at night and it glows then you are having excess fuel in your bank 2. Find out why. Causes are: 1. Leaky fuel injectors 2. Bad ignition wiring harness 3. Broken sensors. When you are done, check out the cat converter to make sure it is not melted. Good luck.
Ran my 95 without cat ECU for years, No shut down and no CEL on dash. Car used to have random bank shut down. Same symptoms---bank shut down after 2o min. Shut car off, restart and problem went away until it would randomly happen again. Disconnected ECU and never had a problem again. Maybe 95's are different
The '95 355 has two computers and two TCU as well as two Slow Down Light. The computer can independently figure out which bank is running hot. The 2.7 Bosch firmware is based on the 348 firmware which did allow the disconnection of the TCU. The '96+ has one computer (with only one temperature protection pin into the CPU), three TCUs and only one SDL. Which means all three TCU output signals are brought into the CPU via a wired-OR configuration with active pull up resistors. If one signal is disconnected, it is pulled up to active state and causes the computer to turn on SDL. That is probably a safer thing to do if you have a temp protection unit, you do want to know if the unit is disconnected.
Also, I think a faulty fuel pressure regulator can lead to a rich bank, as fuel can leak into the vacuum line connected to the FPR, allowing the unmetered fuel to get sucked into the intake plenum. That could lead to all sorts of funny issues, including hot cat on that side, lean condition on the other side, rough idle, etc.
A fuel regulator can actually cause that IF it is bad. However, in all my years working on the 355s, I have rarely see a bad regulator. Check your fuel pressure to be sure. What I have seen multiple times is bad wiring harness.
Question for you. WHEN your car went into "shutdown" (on one bank) , would you get a SDL? I am under the impression that a faulty SDECU (or thermocouple) will lead to dropping a bank AND a SDL?
I unplugged mine when I had test pipes and had SDL solid on the dash. They're plugged in now that I have cats and one occasionally lights up but then goes away - usually only if the car is started warm and driven for a minute or two making me think it's a thermocouple issue and not an ecu one. It's rare enough that I just deal with it.
