1999 550M Limp Home Mode ... what causes it

Hi all,

I am new to this site so I hope I explain this recent problem correctly.

I bought my 550 in Jan of 2012. It was a one owner car with 5,800 miles showing and accompanied with all appropriated service records. I've driven it nearly 6,000 miles since then without a single problem until today. I had driven it at both highway speed and in town (30-40MPH). While leaving town for home the engine paused and then began to run rough. The check engine icon illuminated and the messages "Check Engine" and "Slow Down" alternately displayed in the multi function display window. Oil pressure and oil temperature appeared normal. Water temperature seemed a little cooler than normal though it was 90+ degrees outside.

Remember reading about a similar problem reported in the notes detailed in a report prepared by the Edmunds road testers in their long term test of a new 2001 550M, I drove home slowly while continuing to monitor all gauges.

Once home checked the oil level and found it to be normal both in color and quantity. (Note: Later in the day I checked the expansion tank. Fluid level was quite low but the tank was definitely not empty).After checking the oil I got out the Edmunds report and noted the following comments:

July 2002; mileage 1,624 ... "After stalling the car at a traffic light and restarting the engine, the Check Engine Light was flashing on the dash alternating with a Slow Down warning while the car was still stopped". Though the engine was running roughly and revved reluctantly (they later surmised that 6 of the 12 cylinders were operating), the road testers elected to drive the car to their garage. This resulted in the engine running smoothly after a few miles though the Check Engine light was still illuminated. In my case the engine 'continued' to run roughly and at dramatically reduced power all the way home.

They took the car to the dealership they bought it from, The Auto Gallery (Woodland Hills, CA). where " The dealer quickly diagnosed the problem as a faulty ECU temperature sensor."

The next weekend the same intermittent problem returned after 30 minutes of driving so it was returned to Auto Gallery. Taking possession of the car a few days later the road testers were told that after more diagnoses and road testing the dealership technicians discovered that, inside the fuse box, the connector for the engine management system (EMU) had worked its way loose. The road testers were told that this can happen in normal driving. This problem has not reoccurred.

Does any of this make sense to anyone?

So I opened the fuse box with my owners manual in hand(5.18 - 5.21) only to discover that no reference is made to an EMU. There were however two A10 fuses (#8 and #9) that are associated with a separate "ECU" for cylinder bank 1-6 and 7-12.

So I quickly pushed down on all the fuses (except for #'s 25 - 29 which I haven't found yet) and the 19 remote control switches. I did the same on the wiring harness connections but with a much lighter touch and then restarted a still warm engine. Start-up was normal in typical Tubi tone but only briefly then ran rough. Once the engine was started the 'check engine icon illuminated. The multi function display went through what appeared to be its normal cycle and the flashed the "All OK" message followed by the "Check Engine/Slow Down alternating messages.

I tried once more after the engine was cooled down with the same result though this time the engine sounded weak and revved reluctantly (no higher than 2500RPM was attempted) as soon as it was started.

There are no local shops with Ferrari maintenance experience and the nearest dealership is 175 miles away to the north in the Chicago area.

Suggestions/ Recommendations/Solutions??

 

Faulty ECU tempurature sensor, ? What is that? where would this be located. Is there a part number for that, never heard of it!!!!

 

456, Louie posted this twice...and is new....

I think he was speaking of the CAT ECU...See my response... and add anything you might have......

http://www.ferrarichat.com/forum/456-550-575/415546-999-550m-limp-home-mode-cause-solutions.html

Regards....

 

When you say "limp home" it reminds me of the situation we had with our car about five years ago.

A nice weekend away with my wife when mid-trip we lost a good deal of power. Decided to flat-bed the car to Ferrari of Seattle who determined that one (of the two) fuel pumps went out.

As soon as they advised this, it made total sense.

After determining the problem, the bad fuel pump was replaced and we were back to normal.

 

I had the exact same issue with my 98 550 the day I bought it. Turned out to be a cracked pressure line on one of the fuel pumps inside the tank. The pumps had previously been replaced, but these hoses had not. The crack was such that the car would idle but not provide enough pressure for it to run much above 2500 rpm. The check engine codes were from misfires on all cylinders on the bank that the fuel pump served.

Swapping the hose fixed it.

 

While my car never went into limp-home mode, I did receive a CEL and Slow Down warning at the same time. Ended up being both of the CAT ECUs (in the engine compartment, one on either side) and the two CAT probes. Solved my problem. Please let us all know the eventual resolution of your problem. Regards, Frank

 

It's much better to plug your car into a computer to diagnose its ailment. But you might be able to solve this with a traditional shade tree diagnosis. My guess would be the CAT ECUs. They are located on each fender in the engine compartment and are about the size and shape of a cigarette lighter. The originals are black. The replacements are green. As is the case with many Ferraris, the 550 is designed with two sets of everything that run like twin engines. My guess is that one of your ECUs failed due to age and heat cycles (they crack). So the car thinks that one of your cats is overheating and so the engine management system shuts down that bank and you limp home on 6 cylinders. It's a real sled with only 6 cylinders, isn't it? Find out which side is shut down and then switch the ECUs. If the other side is then shut down, you know that you have found your problem. If that's it, buy two new ECUs, because the other is going to fail shortly. If that isn't it, it could be any of the systems that have twin components and you just need to track them back to the failed unit one by one....or buy a Leonardo....or flatbed to someone who has one.