348 348 ecu error 4121 and ccu delete

This is a job for Qavion...


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Nope... This is a job for @m.stojanovic, @Ferrarium, @yelcab and a few other 348 specialists

I do have a wiring diagram or two which may help, though..

Motronic 2.7?

But yes, they do look like the right plugs.

 

Now that I think about it, only the Ferrari 348 2.7 Motronic thermocouple ECUs (or catalytic control sensors as you call them) have an input into their respective Motronic ECU. And the Motronic ECUs put on the CELs.

2.7 diagram here:

https://www.dropbox.com/t/084U53gkSs8wNcGG

I don't know what signals the Motronic ECUs are expecting from the thermocouple ECUs on these cars. Disconnecting the plugs on these cars may only extinguish the SDL light, not the CEL on the 2.7(?)

The easiest way to prove that disconnecting the Thermocouple ECU plugs generates a CEL on the 2.7 car is to disconnect the right one and go for a drive

 

Are thermocouple ECU faults latched in the Motronic ECUs? Do you need to clear the fault to prove that the plug disconnection worked?

 

Disconnecting the thermal couple and its controller board on the 348 does eliminate the SDL and the engine CEL code. However, if the car was stumbling, it means something is bad with the engine on that side. Are you absolutely sure the cat converter is not heating up? How did you verify that?

 

I see that the 2.7 Motronic ECU does shut down a bank if the temperatures are high (whether real or due to thermocouple ECU/thermocouple faults)

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If the light is still on with the thermocouple ECU disconnected and the (EDIT) "CAT Temperature too high" message is still appearing, how could a CEL be generated by real temperatures?

 

I just realised code 4121 doesn't illuminate the CEL (at least not on the F355). See last column.

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As you say, Mitch, this could be a real problem (but one which doesn't generate codes).

Thermocouple ECU failures show as a different code: 4122

 

4121 Catalyzer temp ECU (fault)
4122 Catalyzer temp too high

These are from the 348 Manual: Image Unavailable, Please Login

 

I wonder if the 355 (2.7) manual is incorrect or if the two cars are different. Comparing the two WSMs, the 348 manual does seem to have more reliable and detailed information on the 2.7.

Would you agree that the dotted line is the final line of a two-line description? If so, that would make the 1212 code applicable to both additive and multiplicative.

 

I can confirm that 4121 means faulty temp ECU - I had this code on one bank of my 348 (2.7) when its Temp ECU was bad and I also get it if I disconnect a Temp ECU. The code is "silent", i.e. it does not cause SDL or CEL and does not affect the engine running in any way. This is on my factory non-CAT 348. On the versions with CAT-s, the 4121 may not be "silent" (others can advise).

Justin, if 4121 is also a "silent" code on versions with CAT, then your CEL is not related to the Temp ECU but caused by something else. I tend to think that this is the case because, as I understand, your CEL did not come and stay on permanently after you disconnected the Temp ECU but remained intermittent, i.e. same as before the disconnection.

 

If you have a cat converter and want to leave it on, it is imperative that you have a working Thermal Monitoring System. I would change the thermal couple, and then the cat ECU if the issue persists.

 

Unfortunately, the manuals don’t go into enough details regarding the fault logic. How does a Motronic ECU define/determine a faulty Thermocouple ECU?

The fire detectors on a modern jet engine will not register a fire if the temperature rise is instantaneous. A real fire takes time to heat up the detectors. So the system registers a fault rather than a fire.
Similarly, if the temperature rise is instantaneous on a 348 due to a faulty thermocouple or thermocouple ECU, does the ECU flag this as a fault rather than a “fire”?
BUT, the output from the thermocouple ECU to the SLOW DOWN does not go through the Motronic ECU on the 348. A different wire is used and it goes to the light directly. The light itself is not smart. If the light sees high temperatures it puts on the light, irrespective of the Motronic ECU evaluation. You might conclude from this that the thermocouple is not detecting high temperatures. Maybe the ECU is actually faulting the thermocouple ECU because the cat is showing too cold for too long? (even though, say, the water temperatures indicate that the car has been running long enough to heat the cats).

But what then is causing the stumble?

 

The easiest/cheapest first step to a resolution is to simply swap the thermocouple ECUs to see if the fault swaps sides.

 

It's not a mystery, that's because that code is for crank sensors, and with the engine not running, it can't read the pulses. That's why you get it pulling codes with the engine off every time.

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On the 348, the relationship between the Temp ECU and the Eng ECU is very simple - the Temp ECU is connected by only one wire (Violet/White) to the Eng ECU, to Pin 52. During normal operation, this wire is at zero volt which the Eng ECU understands as "all is well". When the EGT reaches the "danger zone" the Temp ECU will send (switch on) 12 volts through this wire to the Eng ECU which will shut down the bank.

How does the Eng ECU know that the Temp ECU is good: At ignition "on", the Temp ECU will send a 12V pulse of 2-3 sec to the Eng ECU Pin 52; if this pulse is absent (bad or disconnected Temp ECU), this will cause code 4121. The said 2-3 sec. pulse will also briefly light up the SDL at ignition "on". If any of the SDL's does not briefly light up at ignition (and the bulb is good), it means bad or disconnected Temp ECU on that side.

In summary, all information from the Thermocouple is processed only by the Temp ECU which controls the SDL and decides when to switch on continuous +12V to the Eng ECU Pin 52 (for bank shut-down).

 

So this is the only time the (348) Temp ECU output is monitored by the Motronic ECU? There is no continuous monitoring of, say, out of range/nonsense data?

If you pulled the plug on the Temp ECU with the engine running, would it not generate a code?

 

No data related to the EGT levels are sent to the Eng ECU. The data are processed only by the Temp ECU. The Eng ECU sees only the following on its Pin 52: 2-3 sec. pulse of 12V at ignition, 0V during running with normal EGT and 12V when the EGT goes too high. I do not know whether 4121 will be generated by the Eng ECU if, after it has received the 2-3 sec. pulse, the Temp ECU is unplugged during engine running. I guess not since the status "0 volts" at the Pin 52 will not change at disconnection, unless there is some internal bias voltage on Pin 52 which would signal to the ECU that the Temp ECU is unplugged. Something to test on the side with a known good Temp ECU.

 

Thanks, Miro. I didn't realise that the 348 (2.7) and 355 (2.7) were completely different. I see the Temp ECU part number is different for these cars. I thought because they both have 4 wires on the 4 pin plug that they operated in a similar manner (The 5.2 has 3 wires)

 

The first generation Temp ECU on 2.7 348 has 6 wires (6-pin plug, seen in the post #1) for connection to the loom. I do not know about the 4-pin unit (second generation?) but it should function in the same way as the unit with 6-pins. Actually, in the case of the 6-pin plug, two of the wires are for ign. +12V, two wires for Ground, one to SDL and one to ECU pin 52 (see the attached wiring extract). These were probably rationalised down to one wire each for +12V and ground making a total of 4 wires in the second generation Temp ECU.

Yes the Temp ECU functions in the 348 and the 355 are completely different:

348 - The Temp ECU receives the signal (voltage) from the Thermocouple and, based on the level of that voltage, the Temp ECU "knows" the EGT and takes actions as required: flashes the SDL, switches the SDL permanently "on" and switches constant +12V to Pin 52 of the Eng ECU to shut-down the bank.

355 - The Temp ECU receives the signal (voltage) from the Thermocouple, just amplifies it by 100 times, and sends the amplified voltage to the Eng ECU. Based on the level of that amplified voltage, the Eng ECU "knows" the EGT and, when required, flashes the SDL etc.

We can say that the 348 Temp ECU is a kind of a "processor" and that the one in the 355 is a dumb voltage amplifier (does nothing else). This is why the 355 unit is much cheaper (still very expensive for the simple function it performs) than the 348's one.

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Actually, I was probably thinking of the 4 pin Motronic 2.5.... or the F355 2.7. There doesn't seem to be a 4 pin version on the 2.7 348. Well, I only see one part number.

Probably why Technistrada hasn't produced a budget version of the 348 Temp ECU yet.

 

Here is what I would have done.

1) swapped the cat temp TCUs from one bank to the other to see if the problem jumps sides

If the problem stays on the same side:

2) swap the crank position sensors to see if the CEL jumps sides

If there is an occasional stumble, I have my money on the crank position sensor, and/or the wiring for the connector to the crank position sensor.
I would check to make sure that the crank position sensor/s are not contaminated with oil,
the condition of the wiring behind the plugs is in good shape,
and are properly fastened and gapped from the crank pulley.

3) condition of the camshaft position sensor on the back 1/4 intake cam
I would make sure that the wiring/connector for that sensor is clean and in good shape. I would also have a look behind the cover to make sure that it has not been contaminated with oil.

4) the condition of the pins inside the T55 connector.

If they are plain Junior Timer pins = they can get gapped and not make a proper tight and firm contact with the male pins of the Motronic ECUs.
If they do have gaps in them I would replace them with tin plated Junior POWER timer pins. I would also take the time to deoxidize the male pins on the Motronic ECU.