No CEL (Check Engine Light) 1-4

Dear F-enthousiasts, Can you please help me out?!

Since this saturday my F355 GTS (1997 / Germany delivered / European ) does not run on all 8 cilinders.
I think it runs on 4 cilinders.

When the key-contact is on the Check Engine Lights [SLOWDOWN 5-8] and [CHECK 5-8] light up.
When I the motor is started and is running these cel-lights go off (just likt the are supposed to, i guess).
And, when the motor is running there is no CEL warning at all.

So the problem is that the Check Engine Lights [SLOWDOWN 1-4] and [CHECK 1-4] do not light up at all,
(not at key-contact, nor after the motor is running). And the motor runs on 4 cilinders.

My F-garage advised me buy a new Cat-ECU.
To be on the safe side, I interchanged both current Cat-ECU's of my F355 to find out if the abovementioned problems would also change (from cilinder 1-4 to cilinder 5-8).
Unfortunately nothing changed; the problems stay the same as stated above.

Please, can any of you help me out here (how to solve the issue or how to address the problem)??

Thanks in advance,
Robert

 

1997? If you have two sets of CEL/SDL lights, then I assume you have a 2.7 car. No lights at all suggest that you're not getting power to the lights. I don't know why your F-garage is suggesting a new CAT ECU.

It might possibly be a power relay problem. Relay "L" (RH Bank injector ECU... Check your driver's handbook for confirmation) provides power to both the CEL and SDL lights. Reseat, percuss, interchange or replace this relay (in the passenger footwell).

The RH ECU controls relay "L". The ECU and CAT ECU provide individual earths/grounds for the lights. If a new relay doesn't fix the problem, it might possibly be a connector or ECU problem. I'm not sure where the "rear connector" is on the 2.7. If the relay and connectors are ok, I would interchange the Motronics ECUs.

It may be a cheap fix. Good luck!

2.7 Ignition/Injection Wiring Diagram

RH Bank Wiring Diagram

P.S. The relay is also known as "E5"

 

Regarding the instrument lights, check the obvious - make sure the Check Engine Lights [SLOWDOWN 1-4] and [CHECK 1-4] bulbs are in place and they work.

 

Regarding interchanging: If relay "Q" (E9) has the same part number, this would be a good relay to interchange. It only affects the fuel filler flap.

 

Assuming it's a 2.7. Check your wiring harnesses near the driver side ecu for bent / corroded tines. If it doesn't light up, the left ECU isn't powering up. As mentioned above, it could be a relay, but if service was recently done and the connectors were handled, it's highly likely there's a fouled electrical line that the ECU needs to turn on.

I had the same symptom and the car would fire with just the passenger side ECU and cylinders. Turned out to be a bent tine. Unbent so that it slotted into the other side, zero issues since then.

 

I just checked the Ricambi part diagrams. Relay Q and L appear to have different part numbers, so don't interchange them. I guess you could interchange relays L ("E9") and O ("E13") to see if the problem switches to the 5~8 bank.

Check the small plug under the ECU in this Ricambi diagram. It may be plug "41051" (in the wiring diagram) which interfaces with the relay and the wiring which goes to the instrument binnacle.

https://www.ricambiamerica.com/car-diagrams/ferrari/v6-v8/355-group/f355-m2-7-1995/injection-device-ignition.html

 

What a great response, from all over the world.
So many thanks to you all!! Thank You all for the immediate and constructive replies.
It gave me enough material to continue the search, and it solved my problem!!!

Especially, thanks to Qavion (Ian), because (i) I learned that my F355 GTS is from September 1996 and has a 2.7 Motronic ECU,
and (ii) the cause of my problems was actually the relay, just like he suggested!!

Yesterday, after interswitching both relays, on contact all CEL and SDL lights worked again!! But then the engine would not run.
(I guess because of the faulty interswitched relay).
After opening and 'repairing' the faulty relay, also the motor ran again, and on all 8 cilinders!! (Bella Musica !!)

Of course, I will order a new relay a.s.a.p, but can anyone tell me if I need to buy the original 'alloy' Bosch version
or does Bosch nowadays better ('plastic') alternatives?

again thanks in advance,
Robert

 

If Miro (m.stojanovic) on the forum is listening, he might be able to help you. The metal cases might have better heatsink properties (?). I looked at a photo of my relay panel and it only had 1 metal relay (the rest were plastic (some clearly marked Bosch, others possibly generic). I'm not sure if they're mostly plastic because I have a '98 car. There are some relays that have critical properties, so it may be best to at least buy a Bosch relay.

Anyway, it looks like we have a win (I'm sure you're greatly relieved)

Cheers
Ian.