Trouble in paradise

If it's the same as my 348, which I believe it is, you may either have a left cat overheat, or more than likely, the system thinks you have a left cat overheat. I had it happen once with my OEM cats but when I changed them to sports high flow cats the mechanic disconected the sensor. Said the new Cats were designed to run at a different temp anyway so the system was pointless.

I believe the system throws a spurious overheat reading far more often than a cat genuinely overheats so I wouldn't worry overly but you can either check the temp on your left cat (think you can get a laser thermometer thingy to do this) or just switch the sensors from one side to the other. If this gives slow down lights on the right side you know it's a sensor fault not a cat fault.

 

Is it a 2.7 car? If so you can disconnect the wires from the cat ecu on the left bank, if the power comes back you'll know it's the cat ecu(common problem) or one of the sensors, you can swap sensors left to right to see if the problem moves with a particular part. Slow down light would suggest its cat ecu/sensor related

If the power doesn't come back then then it's something else, throttle pot, fuel pump, coil, ecu, any could take the whole bank out, again you can swap parts between banks to see if the problem moves

 

Seems cats are just too much trouble waiting to happen.

 

More than likely the cat ecu. Swap left to right and see if it changes sides.

 

Yup, cat ECU. Easy fix, Ricambi, get the green ones. I'd go ahead and do them all.

 

As the others have said, cat ecu's. Swap em from side to side to see if the problem jumps sides.

On a side note, what are you coolant temps while driving?

 

What am I missing? Everyone is jumping on the Cat ECU sending a bad signal. Unless I read it wrong, he said he took a temp reading and got 165ºF and 400ºF. Can a bad cat signal cause a physical issue? If not, that's not Cat ECU throwing a bad signal, its a possible real problem. A failed cat blocking flow? a bad injector? Burned valve? Pure guesses... I'm not qualified to say. Get more expertise than I can provide.

Ohh...wait...The 400ºF is the normal bank...the 165ºF is the non-firing bank. Nevermind...I'll shut up!

 

The modules , there are 2 , are about the size of a package of cigarettes, and are located in the left and right rear of the engine compartment.
The reference to 'green' ones is referring to the epoxy coating used to seal the modules.
The epoxy coating colour was changed on the newer modules and they seal better than the original ones.

 

Did you pull the codes?
Did you thermal scan the cats?
If so what were their temps?

 

Try swapping the modules lft to right and see if the problem switches sides as others have suggested.
Disconnecting the modules will not diagnose anything.
Its possible you actually have an issue and are dumping fuel into the exhaust and the ecu's are working correctly.......however before you go there you should try swapping the ecu's.

 

You in LA or La? If LA, plenty of guys around here, so probably easy to get somebody to look at it.

 

Originally you had the left slow down light.......on restart you had the right slow down light but unplugged/ reconnected the modules.
Is it possible this caused the new slow down light? Is everything plugged in correctly?

I would first read the cel codes.
Then, I would start fresh......erase the codes (disconnect the battery for a minute) and restart the car letting it 'relearn' (idle, no a/c, fan off and no gas) for 12 minutes.

Then see what happens with the cel light.

 

What

Is

The

Coolant

Temperature

When

The

Slow

Down

Lights

Come

On

???????????

 

Here is the deal, something is causing your slow down light to come on.

What?

The possibilities:

1) Faulty catalytic converter temperature "ecu"
2) Faulty thermocouple
3) overly rich air/fuel ratio
4) Failed catalyst matrix

 

Okay then move on to the next thing if swapping the cat ecu's didn't cause the light to jump.

If it were my car I would pull the cats and inspect the condition of the matrix inside them.

 

Fixed it so Ernie could read it.

 

If a cat is no good it means it melted inside and is now plugged. It's just like stuffing a banana in that side. No where for the exhaust to go. The only way to know for sure is to take it off and look inside.