456 wont start. Need help troubleshooting.

In case you need it : This is a diagram of the inside wiring circuits for 456...its is the mirror view on the backside and split in 2 for more visibility.

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Guido

 

Do you have a buddy with a 355 or 550? If so swap the alarm units into your car. Obviously you will also need to use the donor card alarm fobs.

I had a 550 do this to me. Thing would bleep and do all the right things but would not start. Swapped in a 355 alarm set up..and away she went..

 

Make sure the F355 is Motronic 5.2 before looking for the alarm.

 

Hi Colby, I know this is an old thread, but I'm having the exact same issue with my 456M. What was the final prognosis of the no start issue?
What did you have to do to resolve it?
Any help would be greatly appreciated!!

 

So it's cranking, but not starting... and the immobiliser generally appears to be responding to the fob?

Do you know if the fuel pumps are producing pressure when the engine is being cranked? Note that the F550 primes the pumps for a few seconds when the ignition is turned on for the first time, but thereafter needs cranking to reset the pump priming logic. I don't know if the 456M is the same.

The 456M workshop manual is a little ambiguous in it's descriptions. I'm not sure if the Right Motronic ECU or both ECUs need to see an rpm signal from their respective crank sensors during cranking before the fuel pumps and the ignition/injection system is activated.

Does your car have an OBD2 port for diagnostics? Are you in Europe, the USA or elsewhere? Please fill out your profile with you car, country, etc for future reference

 

Sorry, car is made for north America.
yes there is an OBD@ port, but apparently the scanner cannot communicate with the ECU's. Can the ECU's or Immobilizer be the Issue?
No power to fuel pumps or injectors.
crank sensors have been switched out and do seem to be the issue.
Not sure about the fuel pumps producing pressure, I will check and find out.
I will update my profile as well.

 

Was the immobiliser disarmed prior to your attempted scan? This is required for scanning. Yes, the Immobiliser can cause these issues, but it seems unusual given that the immobiliser seems to be operating (e.g. cranking is enabled).

No power to the injectors and fuel pumps probably means the Motronic ECUs are not activating the Q and U relays in the footwell.

I haven't pieced together a wiring diagram for the immobiliser system for the 456M. I'm just wondering of the RH Motronic ECU acts as a master as it does on other F-cars. i.e. the immobiliser only talks to the RH ECU, but the Right ECU enables the Left ECU. Have you tried swapping the ECUs? I don't really recommend swapping the ECUs if they haven't already been swapped in the car's history but sometimes it has to be done as part of faultfinding.

Have you checked the fuses for the Motronics ECUs?

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I have wiring diagrams for the engine stuff if required.

 

Tested all fuses and they are fine. The fusebox seems to have had some burnt areas that were repaired recently.
Wondering if a damaged fusebox could be the culprit as well?
Is it worth removing the ECU's and Immobilizer and having them tested?

 

If the fusebox has had issues in the past, I would be running some tests on the relay panel first. I would determine if the ECUs are sending the right signals to relays Q and U for example.

With the ignition on, I would check for relay Q output volts on plug J pins 9 & 10.

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Also check relay U output volts on plug G pins 4 & 5

Don't pull these plugs, just use a sharp voltmeter probe to touch the contacts.

I've just noticed a discrepancy between my wiring diagrams I created and Guido's circuit board in post #26. Guido's diagrams are usually correct. Perhaps you could pull relay Q and check for live battery power on relay socket contacts 30 and 86 (using a voltmeter). Repeat the process for relay "U". I assume the relay pins are marked. After we have determined that the basic functions of the ECUs' are ok, we can focus on the immobiliser side of things.

I'm assuming you have a basic multimeter for checking voltage and resistance and you know how to check for voltage and resistance? If not, now is good time to learn A lot of the problems on these cars are electrical.

Let us know how you go.

 

Ok, will will check the board first and let you know.
thanks for all the advise to date.

 

ok, sorry for the long delay in responding.
As the fuseboard seemed to be having problems, went ahead and ordered a new fuseboard from Guido through Red Bay parts and had it installed. everything in the car seems to work, horn, lights, wipers, lights, a/c, etc. , but still no start, just cranking over.
Tried to scan again and could only get into left side ECU bank 2 (7-12). Pulled both ECU's and reversed Right and Left ECU and rescanned. Again only able to get into bank 2 (7-12). Does not seem to be able to get into bank 1 (1-6)
Does this mean both ECU's are working as i can get into each one when it is in bank 2 position?
Is Bank 1 the master ECU?
Does bank one control the start function when cranking?
Can the immobilizer still be an issue locking out bank 1 even if it seems to be working properly?
What can be the cause that we cannot get into bank 1 to scan?

 

Does your car have an OBD2 port or are you accessing the ECUs via their respective 3 pin plugs (near the ECUs)?

The starter (cranking) is controlled purely by the Immobiliser.

Unfortunately, I don't have a full immobiliser diagram for the 456M, but generally speaking, on Ferraris, the Right ECU is the master and the fuel/ignition circuits in that ECU are unlocked by the immobiliser. The Right ECU then sends an OK signal to the Left ECU to enable that ECU's fuel/ignition circuits. I don't know what kind of signal goes between the Right and the Left ECU. i.e. whether it is a simple earth or voltage or if it is a coded signal on the CAN Bus.

Normally, to get diagnostic data from the ECUs (5.2), the immobiliser must be disarmed. This is the confusing part. You can read the Left ECU, but not the Right. I would have thought that the Right ECU would have to be ok before enabling the Left ECU.... The Left ECU is responding, but the Right ECU isn't. There can't be an internal fault in the ECU because you have swapped ECUs and the problem didn't transfer.

Maybe you can run through the basics... Can you confirm that you are getting power to the Right ECU?

Battery power: blue/red wire on pin 26 (live battery volts)
Ignition power: yellow wire, pin 56 (ignition needs to be on)

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The wire colours are just for information (you won't be able to see the wires unless you pull the backshell off the connector.

I'll try to see if there are any other critical voltages going to the ECU.

 

Can you check the continuity between the OBD2 port and the Right Motronic ECU plug?

There is a blue wire going from the OBD2 port to pin 60 of the ECU connector.

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ok thank you.
good place to start.
I'll have this checked and let you know what if find out.

 

Hi Qavion,

Ok, checked power to the right ECU and has power to pin 26 and ignition power on pin 56.
Was reading up on CAN Line issues and did some investigating.
Found no resistance between CAN H and CAN L, seems like there is no connection?
I believe on most Can systems you should get 60 ohms if the system is working properly.
Checked power to ground and found 11.1volts on CAN L and 0 volts on CAN H.
Unplugged main ECU's, immobilizer ECU, ABS ECU one at a time and checked for resistance.
No change.

Do you know what the actual resistance and voltage readings should be for the CAN system?

Do you think there is a break in the Can Line system or faulty ECU?

if so,

Do you have a wiring diagram for the Can system in order to trace further?

 

The 120 ohm CAN line resistor can be seen in this diagram (RH Engine), attached to ECU pin 85 and 86

https://www.dropbox.com/t/PLerMDdvVX4xFdUI

The CAN line goes to the other ECU (on the same ECU pins) via connector 31L/10L

https://www.dropbox.com/t/pZYk9Wl4fZR64OZ7

Note the splices S105L & S107L. There is wiring going from the splices to connector 24F/27L. This wiring goes to the ABS computer. The ABS computer also talks to the Left Motronic ECU.

I'm not sure why you're not getting 120 ohms between the two wires. You would have to make sure that all computers (ABS and Motronic) are disconnected when doing tests. I don't know what resistance the internal circuits might present to the ohmmeter.

Note that the resistor may even be hidden inside the Motronic connector backshell. I've seen this on the F355.

Diagram links will expire in 7 days.

 

ok, this helps alot.
I'm wondering if the 120ohm resistor has shorted out or is faulty causing the issues with no communication?
where would the most common locations be for the two 120ohm resistors?
Are they stand alone or built into the ECU's?

 

I don't know how many resistors there are. My F355 only had one for comms between the (only) Motronic ECU and the F1 TCU.

If your car is like the 5.2 system on the F355, it will be hidden in one of the ECU connectors like this:

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That horrible mess of splices, electrical tape and thermofit is not standard (that was the previous owner's efforts to bypass the O2 sensing circuits). New engine harness now fitted

Check the RH Motronic ECU backshell first. The wiring diagrams don't show a location but the resistor is listed in the RH Motronic diagrams.

I can't imagine these would burn out (and they are well protected in the backshell). I would focus on Motronic ECU to Motronic ECU wiring (for open circuits).

 

Makes sense, since i could not get a resistance value across OBD2 pin connectors 6 and 14.
I assume should be 60ohms like all other can line systems, but wasn't getting any readings at all?

 

The CAN Bus systems on Ferrari's use 120 ohm resistors. If you disconnect the plugs at both ends, you will see 120 ohms on your ohmmeter. However, not all databusses on these cars will be CAN Busses.

I don't understand the significance of pins 6 and 14 on the OBD2 port. My diagrams are not complete, but doesn't pin 6 go to the Immobiliser and pin 14 go to the HVAC ECU?

Are you trying to measure resistance between single OBD2 pins and chassis earth?

 

We used a breakout box plugged into the OBD2 port to check power, ground and can lines
Pins 6 and 14 are marked as can h and can l. is this not a standard for OBD2 connectors?

 

I think these pins are only used as part of the CAN Bus wiring on the Ferrari F430 (and onwards?). These pins on the F430 are connected to multiple devices.

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The F360 is similar to the 456M. i.e. pin 6 goes to the Immobiliser only. Pin 14 goes to the HVAC only. No "external" resistors shown in the wiring diagrams (attached to these pins).

 

ok, so do you think the 456M doesn't utilize Can-Bus for their wiring system?

 

The 456M does use a CAN Bus system. It's just not connected to the OBD2 port. The CAN Bus system allows the Motronic ECUs to talk to each other and to the ABS/ASR ECU and (on the MGTA) the automatic gearbox ECU.

Of course, many of the individual computers (Motronic ECUs, ABS/ASR ECU, etc) can be interrogated using the OBD2 port. Some also have dedicated data ports.

The Right Motronic ECU does send an (immobiliser) unlock signal to the Left ECU. I'm just not sure if this is done on the CAN Bus or on one of the other wires going between the two ECUs.