2005 Dodge Caravan-replaced catalytic converter, but having same problem

dodge
caravan

#1

2005 Dodge Caravan losing power; code read catalytic converter, so replaced but it is still doing same thing. Will drive fine some days, others it loses power or sometimes accelerates when stopping. What else could be wrong?


#2

The problem with this is…

A bad cat is determined by the values being sent to it by the O2 sensors. The problem with that is…if the O2 sensor is bad…it’s the same code as a bad cat.

So the problem may actually be a bad O2 (or multiple O2) sensors.


#3

The symptoms don’t point to the convertor or the O2 sensors.
Did the check engine light come on? Were trouble codes read from the computer? What were they?


#4

Yes, the check engine light is on periodically, but not a constant. The code was P0420, which is catalytic converter efficiency below threshold. When the cat was changed, the mechanic checked to sensors by looks, and it said they didn’t have soot on them.


#5

P0420 is one of the most misleading codes because yes, maybe the converter is not operating efficiently, but it can’t do its job if the “stuff” going into it isn’t right.


#6

@bnpete

“the mechanic checked to sensors by looks, and it said they didn’t have any soot on them.”:

That is NOT how you check oxygen sensors

That mechanic misdiagnosed the P0420 fault code

The root cause is obviously something else, for example oxygen sensors, an exhaust leak upstream of the rear oxygen sensors, outdated PCM software, etc.

I’d ask the shop to look at the car again. Unfortunately, I think it needs more work to complete the repair correctly. If that is the case, perhaps they can apply what you already spent towards the repair