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Thermocouple control unit

posted 15 Sept 2012, 04:51 by Robert Crane   [ updated 15 Sept 2012, 05:00 ]
The car hadn't been driven since last week when it went into "limp mode". Making contact with a few Ferrari mechanics confirmed my suspicions that it was probably a faulty thermocouple or thermocouple control unit that was the culprit. The problem was that there was a chance that the engine would not come out of limp mode even after it had seen switched off. Even if it did, given all the incidents that had occurred it was almost dead certain that it would reoccur. So the options seem to be to either switch off the battery (which is would remove power the memory of the car and remove the fault) or get it fixed. I chose the later.

Luckily, Sal DiMauro from Racing Red was able to make a house call to visit the sick patient. It seems that you can easily enough diagnose the issues but to do so you need the right equipment. This means a computer, interface box and software to read the diagnostics form the vehicle. Once that was hooked it was evident that issue lay with the thermocouple control unit.

There are two of these units, one on each side of the vehicle. They provide the interface from the thermocouple that monitors the catalytic converter temperature.

With the problem diagnosed all that was needed was to replace the unit.

The above shots show the new thermocouple control unit in place. The part is 179278 and can be found here - http://www.ricambiamerica.com/product_info.php?products_id=208023

The photo shows that the unit is held in place by a cable tie, this is not standard. Normally the unit is held in place by two screws through the body and is mounted underneath the Motronic control unit. Having the unit held in place by a cable tie seems to indicate that vehicle had been experiencing issues previously and was left this way so that swapping the units between engine banks would be easier in an effort to isolate the issue. At this stage it was determined to leave the configuration in place and resolve this at the next major service.

The new unit has a green epoxy base, the faulty unit did not.

With a new unit in place it is hoped that the "1/4 slow down" fault will not reappear. A HUGE thank you to Sal from Red Racing for attending to the issues on site.