355 Code P1448 Every 50 Miles

I recall you access the plugs from the top. I'll try and get you a photograph.

 

Two plugs each side:

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Hopefully the same on 2.7 and 5.2 cars. Hopefully you won't need to remove the side cover panels, otherwise you'll need a 3.5mm allen key.

 

Shouldn't need to be too fancy. Any digital multimeter which can show everything from milliohms to megaohms. Most digital meters change scale automatically and can handle different polarity voltages without having to swap red and black leads.

I assume the inboard halves of the plugs go to the sensors, but you know what they say about assuming

Maybe you can pick up some jumper wires with crocodile clips for hands free operation.... and maybe a few longer pieces of wire in case you need to run test wires to local earths (on other jobs).

There shouldn't be power on the wires until you start turning on the ignition, so no safety concerns.

 

The zip tie may be factory...I no longer have my car to compare, but I recall a few zip ties here and there. The wire definitely needs to be attended to, same with what appears to be another insulation break possibly to the right of the clearly exposed wire? At the minimum, I would want to disassemble the plug by removing the pins from it, and either apply some heat shrink, or better yet, splice in some fresh wire to replace that, which is already getting tarnished. A pin removal tool, crimper and pins would be necessary to do this properly and look correct as well.

I think you should still test the O2 sensors as recommended by JohnK just to eliminate that possibility.

I believe what is shown in the second photo is normal. Not a concern. Someone will need to confirm.

I'm trying to figure how these wires got that way...possibly from not being careful with disconnecting everything during a major service? Hard to say.

Also why a spirited drive suddenly caused this to crop up now? You may want to have your mechanic inspect your motor/transmission mounts. They are known to fail, and cause excessive engine movement. I had the issue...engine started vibrating more...it was progressive over time, so didn't notice right away. Dropped it off with my mechanic and he called me immediately...said when he moved the car into the shop, it was not right (vibration), and when he got it on the lift and hadn't even inspected them, saw my shift rod was out of alignment from the engine droop!

 

Good find. If the white* wire which provides power from the fuse is touching earth or a naked earth wire, then this could cause the problem. Scotch 70 tape (self sealing) should provide good protection (it's flexible, sticks to itself and lasts a long time without losing adhesion). The hard part is getting the tape not to stick to itself in the wrong places. To make it look original, unfortunately, that will take a bit more effort (as per Hugh's suggestion). Cable replacement is out of the question as it is part of the engine harness (expensive) and involves an engine out.
I'd still check the heater wiring of each sensor with a multimeter before putting everything back together.

* I mean the wire on the engine harness which correspond to the white wire on the other side of the plug. By the way, if you get the plugs mixed up, remember that the one with the blue tape goes to the pre-cat (front) sensor.

I think the tube in your second photo is one of 8 vacuum sampling (test) ports and not normally hooked up to anything

Item 44 in the Ricambi catalogue:

https://www.ricambiamerica.com/car-diagrams/ferrari/v6-v8/355-group/f355-m5-2-1996/throttle-holders-and-controls.html

 

Sgtpeper, no offense, but form reading this thread it appears you don;t have much experience with diagnosing such issues that are possibly electrically related. Maybe you should just let you mechanic handle it. Here is the thing. The short to ground DTC and blown fuse needs to be diagnosed and corrected. Once done and corrected, the "no activity" DTC may also go away. The reasoning behind this is that O2 sensors don't work when cold. That is why they have a heater. So if they aren't being heated initially by the heater, they won't generate a signal, hence the no activity code may be generated. Ultimately, after sufficient time, they typically get warmed up by the exhaust and start working. But the ECU may sense "no actgivity" before that happens. Thus, the code.

 

That zip tie is not factory. The factory uses a different kind of zip tie. But, using zip tie is a good thing to dress the wires out of the way.

That exposed wiring is bad. If it rubs against a metal frame or something like a thermal couple shield, it would burn out the fuse. The correct fix is to remove the pin from the connector and put heat shrink tubing around the wire. With the right tools, that takes 5 minutes.

The round stem at the end of the air plenum is supposed to be not connected.

 

... and we can guide you through the process so you don't have to take any risks.

A multimeter is a good investment. Half the problems on these cars, if not more, are electrical. I thought you might be able to get out of buying a multimeter for now depending on where the problem was and what items you had handy, but then I realised, without a multimeter, it's not an easy circuit to diagnose with the engine (safely) turned off. Current doesn't start running through the circuit until you start running the engine. The fuel pump and the O2 heaters use the same logic for activation.

 

It's about time someone invented shrink tubing that can be wrapped around wires without removing them

EDIT: something like this...

 

If you buy a multi-meter

1) For testing the O2 heaters. Set the multi-meter to Ohms. Set the range to 100 ohms or as close to that as you can.
2) No need to replace the fuse.

3) Yes. Unplug the O2 sensors one at a time and then connect the leads to the pins for the white wires. You should see something in the range of 5 ohms. The reading may drift a little. That's OK. Zero or a very low resistance is not.
Note: Before connecting the meter to the white wires, connect the leads together and see what the reading on the ohms is. This is the resistance of the leads. If when measuring the heater resistance you get about the same reading the heater is shorted.
4) Yes.

Next, with the ignition still off, switch the meter to read continuity, or an open circuit. Then connect one lead to the position on the harness connector where one of the white wires would connect. Connect the other lead to ground. Do this for each position in the connector where the white wires would connect,, one at a time. One of them should measure "Short" as it is a ground. The other should measure "Open". If both measure Short, you have a problem in the harness with the wire that provides power for the heaters. You should only have to do this for one connector because the power wires for all sensors are connected together. All 4 O2 sensors should be unplugged from the harness when you do this.

 

I’ve used scotch 70 and it’s great stuff. But I didn’t realize it was so easy to pull pins out of connectors to apply heat shrink tubing.

What kind of tool would you recommend? Is it connector specific or generic?

I don’t think I’ve ever seen a tool that I don’t want

 

Looks like you don't have a continuity check on that meter. Thus, use the ohms scale. Instead of "short" and "Open" you should see a low resistance on one only harness wire (ground). If you see a low resistance on both it would indicate a short in the power wire. Then you will have to figure out which is the power wire.

 

Connector specific...there are a lot of tools available. There are three I recall that are most common in the engine compartment of the 355, the Bosch junior timer connectors, the O2 sensor plugs, and the MAF connector.

 

Because they have similar values, I'd say they should be ok . I checked one of mine a few moments ago, and it was 3.6 ohms minus 0.3 lead resistance, so 3.3 ohms. From this sample of one, I can't say if this is good or bad, but my fuse is not blowing and I don't have any messages.

On my car, I noticed a short extension lead between the connectors on the frame and the actual O2 sensor leads. Also, the extension lead had male pins (at the frame) and were mounted outboard on the frame, not inboard (that's what I get when I assume )

For checking continuity, you should be on the lowest setting.

 

Good question. The engine block should be a good ground, however, I saw a few ohms on my engine block before the earths were cleaned, then it went back into correct specification (lower than 0.2 ohms).

 

This is the tool specific to the Delphi automotive weatherproof connector pins.
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