Another P1448 code issue

You can chase ghosts forever on Ferrari's of this era when it comes to CEL's. It is very hard to be sure that one specific condition is causing that kind of CEL because of that reason. That being said you are on the right track of thinking. If you are going downhill in gear and basically engine braking for an extended period of time the exhaust gases passing over the sensor may not be within the range the ECU is expecting. Is that a O2 sensor or thermocouple code?

 

P1448 means you have a faulty cat ECU for your bypass thermocoupler. Easy to test, swap the bypass ECU with the driver side cat ECU and you should now get a P1449 code instead. If so, then your ECU is bad.

 

Interesting.

The 1448 code is triggered if the thermocouple does not see heat when the by pass valve is open correct?

If you are downshifting in third...are you above 3,000 rpm? Must be for this to trigger.

If you are down shifting at 3,000+rpm the bypass valve is open, the engine is working (drag instead of thrust) but generating heat, the thermocouple should sense that heat and be OK.

The fact that it does not sense heat and triggers the light would seem to agree with your opinion on the cause.....especially if it works fine everywhere else.

Must be right on the edge of the temp range in such a long downshift situation. Or the thermocouple is right on the edge of failing

EDIT: BTW, I need to move to Utah. What a pretty place.

 

Or if there is heat when there shouldn't be (i.e. valve wired open), or if there is a faulty ECU. These are other possibilities too. Most likely faulty ECU. I would use my test method above.

 

Long decels from high RPM seem to throw codes for the bypass valve and also low efficiant 02 sensors. If it open and not getting hot gas to the thermocouple it triggers a code.

I run a little scan gauge on the dash and see these pending codes all the time.

Like he said swap the probe lead to see if the ecu is bad most likely just a freak light

 

I've had this P1448 on/off for quite some time as well (98...5.2 Motronic). Once cleared, mine comes back at about 70 miles of driving - no matter what routes etc. I'm guessing that the CEL may be triggered by mileage as opposed to route...that would be easy to test.

 

What is your exhaust setup?
Do you have hyperflow cats?
The recurring multiple CEL problem on my car, including the P1448 code, was solved by adding spacers to the rear O2 sensors after the cats. And rebuilding the Bypass valve.
The bypass valve was rattling pretty bad and was occasionally sticking open a bit.
Everyone said I had to change the ECU's and it was not the problem

 

I have a Nouvalari Sport exhaust - all other components are stock (cats, headers, bypass valve etc). My Nouvalari did not come with the port for the Bypass Thermocouple (I think it was a European version sent to me in error). I have the thermocouple plugged in but off to the side, but it still throws the 1448 CEL light every 70 or so miles. I am not 100% certain that the thermocouple is the culprit though. I need to have the Nouvalari drilled out and reinsert the thermocouple to figure this out for certain. Car always runs strong, with or without CEL on, so it doesn't seem to have a negative impact.

 

I am almost certain it is the lack of having the thermocouple connected...

 

This is true.

Also, it take around 70 miles of driving for the ECU to gather enough information and generate the CEL. You won't get a CEL after 5 miles of driving right after clearing the ECU.

 

Check your bypass valve. Mine was stuck slightly open and would throw the code p1448.

 

Getting p1448 and p1449 simultaneously and have a rattling bypass valve. Could this be the reason for both codes?

 

Pull out your by-pass valve and inspect. It's pretty easy. I bet that is the culprit.

 

My 1997 DOES THE EXACT SAME THING!!!! 70 MILES!!!!!

 

I would also like to add my exhaust configuration. I have Nouvalari headers and a Nouvalari Sport exhaust. the other day I was next on line in inspection the guy waved me up.... and as I was pulling into the day boom!!! P 1448 and I had to put it in reverse and leave so I would not fail inspection. I have had this car for over a year and have not been able to inspect it because of this issue. I don't even have a sticker on my windshield. I do occasionally have long periods of deceleration from high RPMs while approaching a red light.the valve itself sounds like it's working perfectly. I hear it open and close right when it should consistently and evenly.

 

Check all air lines also from your air pump. Mine kept throwing that code and it was an airline from the air pump that had a huge hole in it.
My 355 is long since gone but I'm still subscribed to this thread I guess.

 

Thanks. I will look! from what I understand the air pump located in the back right of the engine bay... is there to add clean air to exhaust gases at cold start...for environmental reasons only correct? Trying to figure out how the air pump and associated hose can be associated with a p1448 code

 

That's it. I guess there are sensors to monitor the amount of air circulating or maybe even pressure. But once I replaced the hose the code never came back. It was a bigger hose on left side of engine if I remember correctly. Not the size of the one going to the bypass valve.

 

okay thank you. Going to take a peek in there and trace the hoses from the air pump and find the bigger one and inspect that one first