456 Fault code help

Figuring out those check engine lights on the OBD I can be a very frustrating exercise.
The best suggestion is to start from the least expensive items and work your way up.
In my case, the first time I got those lights I had to replace the little relays that are directly connected to the Lambda sensors.
Eventually, after some time and miles, I had to replace also the O2 sensors as well.
Lately there was a problem with the butterfly of one of the throttle bodies, that was letting in some unmetered air.
In any case, before you start changing things, make sure none of the small vacuum tubes connecting to the intake manifold are cracked or loose and that all the plug caps are pushed in all the way until they snap.
Good luck

 

Where to start... Pre- or post catalyst exhaust gas analysis at idle in combination with electrical measurements should give you a good idea as to what is going on. You may want to start with simply having the exhaust gas analysed.

In my view, the most likely culprit is the intake gaskets; they are known to become weak from fuel and get sucked in the intake, leading to a significant air leak. I would advise to start there.

Second, lambda sensors and spark plugs are replacement items. Third, the spark plug connector closest to the exhaust on the six pot coils can burn up internally with no exterior signs and lead to a misfire; so one on the left, one on the right.
When checking spark plug leads, there was a recall for them once so they must have had quality issues with them in general.

RPM sensors for Motronic on other cars are known for collecting metal shavings from starter ring gear and give inaccurate data to the computer; could be as simple as that. Though this is usually a problem at high revs, maybe the computer stored a code for it.

Check your fuel pressure regulators (under the 456GT covers on the engine) too, take off the tiny vacuum hose to see if they're not leaking fuel.

I can think of a lot more, including fuel pressure, bad relay for lambda sensor heating, but start with the items mentioned above.

 

I agree with the above post. Hook up a gas analyser and from cold spray a bit of brake cleaner around the intake base and watch the readings. Also have a listen for a leak from the exhaust manifolds(will be more noticeable from cold)as this will also cause huge adaptive value issues. Also, are your slow down lights operating? The 2.7 system is pretty forgiving and usually the slow down will flag before a check engine with a fuel adaptive value issue.....