I am working on a 1995 456, that cranks but does not start. Unfortunately, I do not have an SD1 to diagnose it. All fuses, relays and grounds were checked. Both crankshaft position sensors were replaced. Both fuel pumps are working, and the idle control valves are energizing when ignition is ON. I sent the immobilizer kit, and both ECUs to the dealership, they were checked and reprogrammed, but still the car refuses to start. Any help is highly appreciated. Thank YOU! MM
So an aftermarket immobiliser. What brand/model? Do you know what it controls? Fuel pumps? Fuel injection? Ignition? Cranking? It's going to be difficult to diagnose without proper diagnostic tools. You will have to go back to the basics. I assume you've checked for spark during cranking? Have you checked fuel pressure at the injector rails? When you say both fuel pumps are running, do the pumps run continuously with the ignition on? On this car, I can't remember if the pumps run continuously or time-out after a few seconds. Fuel pump and fuel injection sometimes have some strange logic on these V12's (especially on the later 5.2). For example: Do you or your garage have a compatible noid light to see if the individual injectors are being commanded on? I'm not sure which type your car needs? "Bosch 2"? Does the engine sound like it's trying to ignite the fuel? When did the problem start? After a belt change? Hot weather?
We installed a new original Immobilizer kit from the factory. There is no spark or injector pulse. The fuel pressure on the fuel rail is correct. The engine just cranks, with no symptoms that it's going to start.
I thought the '95 model was a Motronics 2.7 car? I wasn't aware that you could fit a factory immobiliser to the 2.7 If it's a 5.2, then there must be a way of checking the codes with a generic OBD2 scanner. What part of the world are you from? I did have a strange no start problem with my F355 (5.2) which required the technician to plug an SD1 tool directly into the Immobiliser ECU to reset it (on the car). There are just too many unknowns at the moment. However, I assume it would be a fault which would affect both banks. Unfortunately, we don't have any wiring diagrams for the 456GT so that also complicates the diagnosis.
It's a 5.2, and yes it has a factory immobilizer. I was able to find the 456 wiring diagram but was not a 100% compatible to the car. We have replaced the Immo kit + updated Siren. Located in Lebanon.
If you don't have an OBD2 port, there may be a 3 pin plug close to each Motronic ECU which you can plug a scanner into (with the right adaptor). Look for something like this (Search for Fiat 3 pin OBD2 adaptor): https://www.ebay.com.au/itm/392800523308? I use something similar on my F355 (which doesn't have a proper OBD2 port). You will have to interrogate each ECU individually. Some data may not be available, but it may give you some clues. I guess the immobiliser will have to be disarmed to interrogate the ECUs. You will need to get 12 volts from somewhere to run the scanner. I connected the power wires to a cigarette lighter adaptor.
I have received the OBD2 wire and connected it to the first connector next to the ECU, but unfortunately there was no communication when I connected the Scanner. Is it the correct connector? I have included a picture for your reference. MM Image Unavailable, Please Login
I assume 5.2 cars have immobilisers. Did you turn on the ignition and disable the immobiliser? For the left ECU, the 456M wiring diagram shows white/green, brown and grey/red wires (on one side of the plug). It looks like you have the correct plug. I have seen some variations, though, between diagrams and the car, so don't panic if the wire colours are not the same. Regarding your adaptor... Does it have red and black power wires (and are they powered with a 12 volt source?). I can't tell from your photo. Image Unavailable, Please Login Sometimes you have to get the right power up sequence (I can never remember which first... car, adaptor or scanner).
Is the 3 pin plug a good fit? I have seen some Fiat OBD adaptors have a plug which doesn't match properly.
It fits with no issues. I've tried different sequences, but no luck. I'm using a Topdon scanner, I tried to access it by selecting the generic OBD2 function, and by selecting 456 through the scanner as well.
Sorry, I've run out of ideas. Maybe try on the 456/550/575 forum? Maybe someone can recommend a different type of scanner. Sometimes the more simple scanners are best. I have one for my F355 and it only reads codes, no parameters. (EDIT) I've just noticed a battery charger start disable relay in the 456M wiring diagrams. When you say you've checked fuses and relays, did you include this. It's one of those relays above the main panel with a built in fuse. See "37D". I can't remember where the start relay is. https://www.dropbox.com/t/WLo3lueJA4rn93oU How did this problem start? Was it after maintenance or did you (or the owner) go out to the car one day and it didn't start? If your idle air controllers are working, it means that at least some of the circuits in the ECUs are working. The ECUs turn on the power relays for the idle air controllers.
Thank you for sharing the diagram. All fuses and relays were checked including 37D. The problem started with the customer, were the car cranked but refused to start intermittently. Till it reached a point, that the left bank starts for a couple of seconds then switches off, while the right bank is dead. After sent the immobilizer kit to be checked, they reprogrammed it and sent it back. When installed on the car, same issue, left bank starts for a couple of seconds then switches off, while the right bank is dead. We sent both ECUs, they tested them, and informed us that the right bank ECU needs to be replaced, and the left one is fine. We reinstalled them, but right now the car cranks but doesn't start. The idle controllers and fuel pump are working when ignition is ON.
So at the moment you have a bad ECU (right) installed in the car? I had a 360 with a very similar issue. We found the car had software from a Challenge race car not a Challenge Stradale. The race car didn't want to see the immobilizer but it had an odd error for the brake switch that would turn on the CEL. We found the immobilizer wiring was an issue and was not communicating. Once the ECUs were reprogrammed with Challenge race car software left & right, the car started and ran very well. It is possible the immobilizer is not communicating with the ECU. You don't have the option of race car software but it sounds like the right ECU needs to be replaced at least.
Have you tried hooking the scanner up to the Left ECU? (the supposedly good one) I just realised I said left by mistake in my previous message: It's the right hand side which has these colours.
Although not currently at my disposal, you need to get your hands on the Ferrari "Diagnostic Sheets" for the Motronic 5.2 system as used in the 456. This will have a pin by pin ECU breakout that you can perform simple tests with a DVM. My hunch is that the immobilizer is still active.
We got an SD1, and connected it to the car, but still could not establish communication with it. is there a procedure to start the scanning process?
Can you plug the SD1 into the Immobiliser ECU and reset that? When I had a problem connecting to the Motronic ECU on my F355 (5.2), my tech reset something in the Immobiliser ECU using his SD1. This allowed communication with the Motronic ECU. It's starting to sound like the dealer messed up the reprogram.
