456 GT Fault Issues

After the first year of ownership I thought that it would be helpful to share some of the problems I've had and how to fix them !! Note these apply to the early 456, mine is a '94.

Rear Spoiler

Before changing the motor or ecu check that the warning light has a working bulb or even that a bulb is fitted!! - To check: remove the plastic upper and lower covers around the steering wheel which is held on by 4 setscrews, then slacken the two (10mm?) bolts so as to lift up the instrument binacle and then turn slightly around to check the bulbs which are held in by rubber bungs, they are a small standard car bulbs available from Halfords etc.
Check that the spoiler motor arm has not tangled with the wiring loom and jammed - To check: remove the black plastic rear underside cover (self tappers and nylock nuts)
To remove the spoiler motor you can access the three 10mm bolts that hold the motor to the rear support via the rear bumper exhaust hole using a 3/8 rachet and extension bars and a universal joint !! the front lower nut can be undone with an open ended spanner, although you need quite small hands to do this, if not you will have to remove the exhaust box !!
You can check the motor by connecting to a 12v supply, when you refit tie wrap the cable to the rear support to make sure it cannot be caught up by the moving arm. Before you connect the arm to the spoiler switch on the ignition to get the motor to the up position, then connect the arm to the spoiler so that the spoiler is in the up position.

Front Seats

Before changing motors, ecu's, pots and microswitches check that there is nothing under the seat which can stop the movement, on the passenger seat I had the ecu fall down and stop it moving all the way forward, fixed this by removing seat and tighten up the screwes that hold the ecu to the bottom of the seat properly( unlike the specialist that fixed the seats previously)
Also the seat was not always motoring back when accessing the rear seats, I traced this to the seat back cam not always locking when the seat back was pushed back and then not closing the micro switch. You can remove the seat side checks in situ but it is very difficult, I think it is easy to remove the seat and work on it out of the car - beware it is very heavy !!

 

Removing Seat

Move seat backwards, then undo the hex head cap bolts at the front of each rail then move seat forward and undo the 2 bolts on each side at the rear of the rails, lift up back of seat to disconnect the ecu plug from the ecu under the seat. Then lift seat out of car !! beware it is heavy!!! Once out, you can remove the side cheeks by undoing the two self tapper screws at the base of the seat back cover to allow better access to the side cheek screws and then check that the cams on each side of the seat are closing and openning the micro switches properly, also check that the seat is locking when in the upright position, you can also adjust the cable tension for the seat back release.

Sound system lacking Bass

There is a bass amp in the boot behind the CD Changer which has its own fuse, so check that this has not blown - you will have to remove the carpet trim and the CD changer to gain access to the amp fuse !!

The next challenge will be the slight drivers side window gap !!! I will report back when I have sorted this !!!

 

Nice write up. I can voutch for the weight of those seats too, heavy MF's.

I've had my 95 for about a year as well, have put about 8000 miles on it if memory serves. Nice daily driver.

I had on-going problems with check engine lights (1-6 and 7-12) coming on intermittently. Solution was to clean all contacts I could get at. They were very corroded so I used a wire brush and a pick. The rubber covers they use for them get cracked over time and allow the elements in. I don't think you can replace the rubber covers unfortunately, which would significantly improve the weather proofing of the contacts. Some of these contacts (like the mass flow sensor) were put just so that it would catch water; the guy who designed it that way should be lashed. Put dielectric grease around all of the fittings to keep water out, then made sure all connections were tight (more than once). A few rounds of doing this and the problem has gone away.

Another problem I had was that the dash board lights were blinking at night on occassion. Turns out that the light intensity button contacts were dirty (found this out after a while, not the obvious source of the problem). Cleaned it and no more disco nights.

Alberto

 

All good stuff. Many thanks and keep it coming.

So far my only contribution relates to the 456 GT "Slow Down" lights - contrary to received wisdom, the ECU might actually be doing its job. In my case a couple of fouled plugs were causing an over-rich(?) exhaust. New plugs - no problem.

 

I will add stuff as and when I can. The check engine and slow down lights are a bit of a pain as it is not all that easy to trace the cause without an SD1 to look at the outputs of all the sensors etc. so you are not sure if it is a real fault or just a duff sensor or connection. I don't seem to have had the bad connection problems so far!
I also think that as there are so few of these cars made even the specialist are not really that knowledgeable, the WSM is not all that illuminating either and I don't have a wiring diagram for the car, so when it comes to electrical problems I struggle a bit.
My latest problems were caused by the way the alarm had been wired and it took the specialist quite a bit of time (therefore high cost for me) to track down and cure.

So far the first year has cost me double !! what I was expecting, but hopefully next year will be better!!

I do enjoy tinkering with the car and of course enjoy driving the car, so don't mind too much, however I am getting a bit p*ssed off with the price of parts from Ferrari, i.e. front brake pads £500 or the same pads from Pagid £135 !! also a fuel regulator at £400 !! its only a fuel injected petrol engine not the space shuttle !!!

 

Hello everyone, here is my two cents of experience....
I also had the slow down light coming up for one bank at speeds over 90 mph and disappearing at speeds below 80 mph.
It was finally traced down to a faulty relay to which the lambda probe is connected.
The relay is really inexpensive and very easy to get to, so the whole issue was not a big deal, although it helps to have the diagnostic equipment to understand what is going on.
Without it, one can simply switch the relays from one side to the other and see if the slow down light also changes side, although this way one does not see if there are other issues with the engine.

Besides this I had a leaking rear shock absorber that I had serviced by Bilstein in California for a very reasonable amount of money, but for a less reasonable amount of time.

All in all the experience with the 456 has been a positive one.

 

Alfredo, I have a not dissimilar issue with the Slow Down light, except mine is the reverse - light driving it comes on, and when I drive quicker it goes off.
Can you enlighten me to:

1. Relay you changed, part number and where it is located in the engine bay, please ?
2. Where are the Exhaust ECUs located in the engine bay please ? as I'd like to try a first test of swapping them over before spending £450 getting a new one.

Thanks in advance,
Davo

 

Hi, the part number is: 154470 position 42 table 18
Its location is not in the engine bay, but actually on top of the side vents (from the engine bay).
You need to open the hood and you see that lonely little black box sitting atop the vent.
9 times out of 10 they are the culprits.
Good luck

 

Alfredo:

I cannot find the referenced item on table 18 of the 456GT parts book (http://www.ricambiamerica.com/parts_catalogs.php?M=FE&P=&V=diag&I=787). Can you verify where it is?

Thank you .
Alberto

 

It's table 19, the next one to the right. I think you are referring to the Cat temp ecu's, which are located on each side of the car above the wing vents, you have to open the bonnet to access them. If the light is only showing on one bank then you can swap over the ecu's from one side to the other and if the fault moves then the ecu is U/s.

 

That is correct, sorry for the confusion, but my reference is the 456 parts book Dec 1993 edition and other editions are more complete and have more pages.

 

We all know about leather shrinkage on the dash and rear parcel shelf, but I'm seeing the headliner pulling away and sagging slightly in a corner of the roof. Anyone else had this happen?

 

Alfredo,
found it! had me baffled for a while looking in engine bay - but its actually on the wing (US=fender) as you described.

Picture attached for reference.

Passenger side seemed to have 160454 fitted, and drivers side the later 179278.
Now looking through my records, the PO had one fitted by a specialist to cure the problem before.
So I suspect the 160454 one has failed.
I've swapped them over as you suggest, so will find out on my next run out.

Thanks
Davo.

PS. bolts seem to a rather funny size 7.5mm ? had to very careful not to drop the nut and washer underneath into the wing (fender).
Image Unavailable, Please Login

 

As you can see they are located in a spot where they get soaked frequently and that does not help their longevity.
At least they are easy to replace and relatively inexpensive.

 

Hello

I have a 96 456gt and I have the same problem on and off with this ecu I think. But sometimes mine only runs on 6 cyl. when it happens.

Today when it happend I just disconected the ecu, and suddently the 6 dead syl. just fired up again and the engine seam to run perfect??? I drove 20-25 minuts back home without any trouble!?!? (I think!?!?)

Can any one tell me if this is normal and safe? Can I damage the engine driveing without the exhaust temp. ecu? What does the ecu do besides cheking exhaut temp? Everything seams fine to me, but I dont know.

Can anyone enlighten me pls.

Regards Paul

 

Do not disconnect the ECU: replace it!
They are really inexpensive and easy to replace and 9 times out of 10 that is your problem.
The O2 sensors are part of the Fuel Injection system and are there to provide the necessary feedback to the FI ECU.
The feedback is necessary to keep the exhaust temperature from raising too much and damaging the cathalitic converters.

 

I would not run it for long without the exhaust temp ecu connected as if that bank is running too rich/over fuelling (bad O2 sensor which is probably what your problem is) then the exhaust will get very hot(even glow red!! this happened to me) or catch fire, I suspect that the temp ecu is there to cut off that bank if the exhaust temps are too high. Take it too a specialist and get it checked on the OBD diagnostics.

 

Hej,

my lamps came on the other day on the 7-12 bank, but only after it had stood still after refueling it and after some running (basically engine was at full operating temp.). What I tried was just to disconnect the temp ecu and reconnect it again when the engine was shut off. After that the engine ran fine again until we made another stop. I have now swapped the units to see if the problem changes side..

 

Thank You all, I will have it chekt out as you say.

Regards Paul

 

Hej,
I tried to switch sides of the thermo electronic steering ECUs.
This worked to good effect and the failure has now transferred itself from the left to the right bank, in other words, one of these boxes is broken.

A new one is available at eurospares.co.uk at 450 euros, can anyone beat this price?

//joakim

 

Joakim,
Exhaust Temperature ECU Part Number 179278
from www.ferrariparts.co.uk (maranello spares) was about £165 last year

is this the part your referring to ?

 

yes..
better price though at your place

 

now £158.13
deliver is normally about £10 next day.
service is usually very good.

 

don't know how I missed this thread : My right [passenger] side bank is not up to my liking. Happened when I needed to shut off the battery [via cutoff switch] and the ECU's had a terrible time of firing correctly. Actually thought of taking out spark plugs...but after a couple days [must admit, there was black smoke like soot out those rear pipes once ] The started to fire normally.

Guessing the ECU needed, in this case more time to re-set.

However, couple days ago, same side, not firing in way I'd like, with a bit of dark exhaust on a real punch it on fw....wondering if the exhaust ECU like in this thread is a nice way to diagnose the problem?

any insights, just swap them and see what goes?

wife has it today and taking to work, she says it running real great.

r

 

I just had the same issue with my 1995 456 GT. About two months ago the 7-12 slow down light began flashing and the car lost power, feeling like it was running on 6 cylinders. I pulled over, shut the car off, and waited a few minutes before firing it up again. When I did everything was back to normal. I drove the car twice after that without a problem, but then in the middle of a 20 mile trip it felt like the 7-12 bank was cutting out intermittently. You could tell it was 7-12 because the exhaust was noticeably cooler and smelled like hot air instead of smelling like exhaust.

Anyway, when I got home I found this thread and tried swapping the Catalyst Temperature ECU from one side to the other. Sure enough, the problem moved to the 1-6 bank. It appears that one ECU had already been replaced, so now both sides have the latest part number 179278.