Calling techs

What did you switch from side to side? Are you saying you swapped the ECU's and still got the 5-8 CEL? Sometimes a MAF goes bad and you get this.

 

Have you looked at the plugs to see if the 5-8 bank is running rich?

Have you used a temp gun to compare the temperature of the two converters during warmup?

If not, I'd suggest both of the above.

A couple of quick guesses would be that the 5-8 bank is running rich and overheating the converter, causing that bank to get shut down by the thermal protection circuit, or perhaps a wiring/connector issue (most likely causing a rich condition, although it could be in the thermal protection circuit itself).

 

I don't know what the diagnostics are for that code. Is it possibly cam position sensor and not the crank sensor?

 

Have you check spark once it goes rough?

 

4112 is the phase sensor error. You need to replace that or figure out why the ecu is not seeing that signal.

 

If you are pulling the code with the engine OFF it will give you 4112, because the engine is NOT turning and thus the ecu(s) cannot see the signal from the crank sensor. It will do it even with good sensors. So, when you pull the codes be sure to pull them with the engine RUNNING. This will make sure you are getting a genuine crank sensor error signal.

 

Oops-- my earlier response was a result of misreading 4112 for 4121 (converter temp ECU). Sorry about that.

Still might be worth comparing converter temperatures during warmup though.

 

Check your exhaust for leaks on that side. Try looking at the EGR plumbing on the heads to see if any are leaking. Then I'd look for leaks in the exhaust system. Air might be getting in causing a lean condition and the heat. The CEL is indicative of excessive heat so either the sensor is screwed or something is causing the cat to heat up.

Could be unburned fuel - oh, have you checked your injectors for a leaky one? One of my stock units actually had a drip leak. My car runs a little rich and if I coast down a long hill in gear, I can get a CEL from excessive fuel build up in the cat. This goes away when I apply the gas, however.

 

What about the cat ecu connector on the 5/8 side. Maybe a bad wire on the harness side of the cat ecu wiring.

I would get periodic rough running and codes (I think they were injector codes) and it turned out to be a bad connector at the injector. That was on a 355. Just throwing stuff out there. Good luck.

 

I would also check the Coolant Temperature Sensors.

 

Tommy, seeing as how the phase sensor code keeps getting set I'd want to try to eliminate it from the equation. I'm not familiar with the symptoms of its failure in a 348 so no help there. However, I've seen plenty of thermally related failures in this type of sensor. Typically, the insulation on the wire within the coil starts to fail, which results in a short that renders the sensor ineffective once it reaches a certain temp.

My suggestion would be to replace the sensor if you can find a way to do so. As an alternative, you could try shooting electronic component freeze on the sensor after the symptoms present in hopes that would temporarily solve the problem and thusly convict the phase sensor as the root cause.

Wish I could help more but I do hope you'll keep us up to date and post your eventual findings. Good luck in your quest!

 

The Phase (cam) Sensor failure would affect both banks and, I think, the engine would not run.

 

I agree. If it's running rough intermittently it's typically a spark or fuel problem. If you checked for spark and that's ok (but you have to check when the engine in running rough with a spark tester) then that leave fuel delivery/timing. Considering that the phase (stroke) sensor code keeps reappearing and since it controls the injector/ignition timing I don't understand why you have ignored it and swapped every other sensor in the car, none of which are related to the 4112 code. 4112 code is not the code that pops up when the codes are read with the engine off. that would be 1121 (RPM sensor).

Spark tester:
Image Unavailable, Please Login

 

Agreed it would affect both banks. That said, nothing the OP has tried has identified a bank-specific component, and the fact that the phase sensor code has been set repeatedly seems worth investigating.

Incidentally, based on the symptoms the OP described my first thought was a CTS as well. Which is why I suggested comparing converter temps. Since those are reportedly similar, that starts to point toward something that affects both banks.

 

Yes, but, the cam sensor is on the 5-8 bank, I believe. Thus only the 5-8 bank picks up the error. Funny thing on 2.7 cars is that at least one code, I forget which one at the moment, means on thing on bank 1 and another on bank 2. The WSM only tells you about one of them.

[edit] Actually it may be on the 1-4 bank if its like a 355. Still, only one ECU would report the error. But there is the possibility that the 4112 error on the 5-8 bank is the code than means something different on 1-4 and 5-8. I'll have to see if I can find if that is the case and what it refers to.

[edit 2] Sorry, can't find it at the moment. Anyone else have which code(s) have different meaning on bank 1 and 2 on a 2.7 car?

 

On 2.7, that one signal is sent to both ECUs of the engine.

 

Isn't the signal from the sensor picked up by one ECU and the information sent to the other through the ECU communication link? I know both ECUs need the info to time the injectors etc, but do both report the error? I'm not as versed on the 348 as on the 355. The systems, while both 2.7, are different. Even different on the 2.7 355. Early 355 had a phase sensor on each bank. Later 2.7 cars only had one.

Still, the OP's car is throwing that code for a reason and it should be looked into, not ignored.

 

It's tough to follow the diagnostic process you've followed...It that it seems as though you have a recurring error code for the cam phase sensor. Have you put a scope on it's output?

 

+ 10000000000000000000000000000000000000000000000000000000, as long as it is done while the cars is running poorly.

 

There is no ECU communication link. Whatever signals needed by the ECUS are being provided directly to both ECU. In the phase sensor signal, the actual signal of one phase sensor is being connected to both ECUs. The engineer assumes that if one bank is running, the other is also running. I also have to assume that the ECU knows how interpret the bank 2 activitiy to be 90degrees lagging behind the bank 1 phase signal.