I'm still hopeful it was just an old fuse. I'm sure I'm not that lucky though...
The ends of the extenders look very close to the engine frame. In that 3rd shot is there any contact between the braid of the thermocouple and the white wires? The exhaust system will be moving (road vibration and engine torque), so there is a potential for abrasion.
Note he had codes for "no activity" and he said the fuse was hanging out of the socket...so may have been intermittent. Will have to see if any come back
I interpreted sgtpeper's message as the element of the fuse hanging on for life (not the fuse itself). Otherwise why would he replace the fuse?
Alright - I'm sure you are all on the edge of your seat. I drove the car about 50 miles today. When I first drove out of the garage I got a slow down light - when I revved the engine a little it was rough and I heard a little alternator squeal. I think the battery was a bit low because I was messing with the radio for 20 minutes the night before with the engine off. That went away in 30 seconds or less. The rest of the day was fine but after 30 miles the check engine light went on. The car still runs perfectly fine but the light is on. I checked #22 fuse again and it is blown - again. Soooo something is clearly not right there...
Short to ground maybe ring a bell? You had DTCs for all 4 O2 sensors that indicated the heaters were shorted to ground. The fuse that supplies power to the heaters has blown. Something is shorted to ground. Disconnect each O2 sensor and measure the impedance between the 2 white wire. It should be between 5 -10 ohms. If the are all good you need to disconnect the connector to the engine ECU and measure the impedance of each wire THAT SUPPLIES POWER to the O2 sensor and ground. It should be infinite. If it is zero or small, the power wire is shorted to ground. The O2 sensor should be disconnected from the harness when doing this.
For now, I would ignore the 1446 code (temp protection circuit active, bank 1) because if your O2 sensor is not working, the mixture is going to be off. Here is what I think. One of your O2 sensor heater wires are shorted out to the frame. Judging from how close those wires are to the frame, it is going to rub if your engine bounces, torqued, shift heavily. You should...: 1. Remount the cat converter to get 1/2 inch of clearance between the end of the o2 sensors and the frame. Check each of the white wires and replace the sensors that have any sign of rubbing on those wires. 2. OR, get a right angle O2 extender 3. Replace the fuse 4. CLEAR all CEL errors 5. Drive the reset cycle and see what error codes remain.
I looked at the white wires a bit closer - none of them have any exposed material. They aren't in contact with metal - although one side is pretty close. The metal braided connection for the lower sensor was in contact and I pulled that away. Could that have been it?
Not if there was no white wire insulation damage. Time to get out your multimeter and measure the heater resistances (see John's post). Do you know where the square disconnect plugs are for the O2 sensors? Don't keep blowing those fuses or you will damage something expensive.
Thanks for the post Ian. I have been sitting here shaking my head thinking the same thing. I'd be particularly concerned about 1446 since if the cats are really getting hot, since they appear to be after market metal core cats, the core can be damaged long before the fuel gets cut off. I wouldn't be driving the car for miles to see if it was still broken.
You might just have a bad heater in one of those sensors. So, measure the resistance, and see which one is blown. Replace that. Oh, this car is new to you. It is a good idea to inspect all the O2 connectors to see if any of those crimps, wires, or pins are touching each other. You do not know who did what to this car before.
Probably a good autoelectrician would be better. If your guy doesn't have access to decent wiring diagrams, this diagram includes the O2 heater power circuit from the sensors to a 9-pin engine harness disconnect plug near the Motronics ECU behind the passenger seat (#41090): Fig11_1998_F355_5.2_Engine_Control_System The following diagram shows the power circuit from that aforementioned plug to the fuse panel (note that the plug number changes to #41051 in this diagram): Fig11a_1997_5.2_Injection_System_Ignitionv2 It's a purple wire to the relay/fuse panel. These are far more user-friendly than the original Ferrari diagrams. If he can't find the problem within 30 minutes, get a new guy (unless the problem is really intermittent). Don't let him run the engine for too long because of the cat heating problem.
I don't need to flatbed the car there, do I? My mechanic is one of the first Ferrari master mechanics. I think he should be able to find the problem! Hopefully!
If he's local, just drive sensibly. My diagrams will be better than his, so if he has an email address, send him the links The diagrams are especially easy to follow on an iPad where you can scroll and zoom with ease.
Trying to get in to see my mechanic. I keep obsessing over this though. I tried looking at both O2 sensors on each cat and nothing seems to be in contact and the wires all seem just fine. Would a bad heater cause the fuse to keep blowing like this? Would a bad O2 sensor cause the fuse to blow? This all got worse after a decently hard drive. I do remember one my way back from driving in the canyon I smelled a little electrical smell - that sort of metallic smell - while in the cabin.
Well, hopefully. Otherwise it's not just a simple component change, but an engine harness wiring short or O2 wiring to fusebox short. Heating elements in general (electric fires, stoves, etc) can either fail open circuit or short circuit. Sorry, I don't have any data on the most common causes of O2 heater failures. The heating element is inside the O2 sensor on a separate circuit to the sensor element, but I suppose the two circuits would be shorted together. You won't know until you put an ohmmeter on the O2 probe wiring.... only a few minute check per O2 sensor if you know what you're doing. As you can see, in this case, we are not big fans of trial and error diagnoses. For example, a dodgy mechanic might want to grab a bunch of fuses and disconnect the O2 sensors on one bank, then run the car and see if the fuse still blows, then by process of elimination try to identify the O2 sensor causing the problem, but that really would be my last resort if I couldn't identify the faulty O2 sensor or wiring by doing voltage and resistance checks. There are quite a few airplanes which have fallen out of the sky thanks to wiring shorts.
e.g. disconnect the O2 sensor connector on the engine frame and check the resistance (with an ohmmeter) across the white wires (as previously suggested) and then make sure that there is no connection between the white wires and the black wires. Whilst monitoring the resistance on the white wires, shake all the accessible wiring going from the plug to the O2 sensor to see if the reading changes.
Unfortunately, I just don't have a good way to get under the car to unplug it at the sensor here at home. I'm supposed to get a lift at some point so I can have my Porsche and Ferrari in the garage at one time but haven't done so yet.
