456GT - What reasons for "7-12 Check Engine" warning light?

It could be a faulty sensor or it could mean that the cat is getting so hot that's it's about to start a fire.

 

Most good garages will charge nothing or very little to read the codes. DO NOT ASSUME THAT WHAT THE CODE SHOWS NEEDs REPLACEMENT. If it says th O2 sensor, you may or may not need an O2 sensor. It could be dozens of other things in the O2 circuit. Even Pep Boys can read the code for you.

 

I think the cat getting hot light is the "Slow Down" light.

I had a similar problem with my 456, and the only real solution was to take it to the dealer and have them hook it up to the computer, so they can tell why the light is coming on.

Does the car seem to run OK?

 

If it comes on after 15 minutes of driving it could be hot cats, however, on my 1995 456, they go on and off when I hit bumps sometimes. They have a mind of their own. If they flash, then there's trouble (so I've heard). Again, if it comes on when you first start the car (cold) and stays lit, it's probably an o2 sensor.

 

One thing I forgot-- you can try resetting the ECUs by removing all power to the car (use the battery shutoff) for 15-20 minutes, and then start it up and let it idle for 15 minutes without touching the gas.

This didn't solve my problem, but you never know.

 

Hi Guys,

Glad to hear you solve the problem by just reseting the code through the dealer's computer. It's about the same cost over here in Hong Kong around HK$3,000.00 (US$380.00)!!!

While quite a lot of you guys own 1994-1995 456Gt. I would like to enquire if anyone of you had paid for the Cambelt change process and/or 30k major maintenance.

There seems no one over here has any first hand experience at all.

Cheers.

 

Ron Tonkin Ferrari in Portland, OR does the 30k on a 1995 456 for about $5k - Orange County Ferrari will do just the belts and tensioners for $2k. I am awaiting belts and tensioners to arrive for my 456. I plan on installing them myself. I still need to find out exactly how the tension for the belts is checked - the service book says to use the Staeger Tensiometer on the accessory belts but not the cam belt. It appears that the cam belt is under spring tension that is factory set (the stiffness of the spring).

 

Good Luck!!!

I have seen it first hand, while taking the belts off of the V-12 or even putting them back on, the cam rotate about 30 degrees.Due to the tension of the lifter and lobe of the cam.
It bends the valves!!!!

All I am saying is be very carefull doing a V-12 service yourself.
Taking the heads off is not very fun. Neither is replacing the valves.

 

Turns out that the Staeger Tensiometer is required for the cam belts. The tolerances are very tight with the v12 - 1 degree. If your two degrees off, you get check engine lights all the time. The cam must be locked down and the new belt positioned appropriately. The key to the job is patience and a "measure twice, cut once approach."

 

FYI,

The amber 'check engine' MIL (malfunction indicator lamp) does not, will not, indicate catalyst melt-down. That's what the red 'slow down' MIL is for.

Yes, the slow down (red) MIL may only be a thermocouple control unit malfunction. The 'slow down' MIL system contains a thermocouple, which uses a bi-metallic sensor to transduce temperature into an electrical signal. Then, the thermocouple control unit (a.k.a. thermocouple ECU) converts this signal into one that the Motronic engine ECU can understand.

The amber check engine MIL will indicate many other potential errors, as noted in the WSM (workshop manual). One of the usual suspects is the Lambda circuit (oxygen sensor), which monitors the exhaust for oxygen molecules (aka excess-air factor). However, there are many other sensors which may trigger an MIL.

Proper diagnosis is the only way to permanently fix the malfunction. There certainly may be situations which trigger an MIL which can temporarily rectified by resetting the error codes, erasing the error memory by disconnecting the battery momentarily (3- 5 seconds). If one chooses to perform this operation, you should follow up by re-initializing the self-learning Motronic by starting the engine without touching the throttle for approximately 5 minutes. Waiting until the cooling fans come on is a good reminder that enough time has elapsed. The ECU is learning throttle position during this operation.

If you choose to erase error codes without reading them, this may hinder proper repair of the malfunction. It's good data that should be collected.

USA cars may access the MIL codes without a computer interface via pushing the button located near the Motronic unit for > 10 seconds, then reading the error codes as flashes of the amber MIL. The error memory may also be reset using this method. Additional information is located in your car's WSM (always a good investment).

Typically, disregard the crankshaft position sensor error, this is triggered because the engine is not running at the time you're accessing the error codes.

This only applies to OBD I cars, up to 1995.


Best regards,

Rob Schermerhorn

 

That's great info Rob, thanks!

 

Joel,
I had a similar problem on my '95 456GT about a week after I bought it. I fixed mine by re-seating the connectors on the ECUs.
Turn the battery disconnect off. Remove the drivers side and passenger side kick plates and disconnect the large connectors that attach to the ECUs. I used contact cleaner (from Radio Shack) to spray the connector assemblies and then re-connected, disconnected and re-connected the ECU plugs a few times.
When the plugs are re-connected and the battery switch turned on, start the car WITHOUT touching the gas pedal and let it idle for about 10 minutes so the ECUs can re-learn the throttle settings.
My warning light has been dark ever since.

Rick . . . .