View Full Version : Cat Converter Overtemp?

01-17-07, 03:25 PM
Does anyone know how the PCM determines Cat Converter Overtemp?

When I go up a hill, or accelerate from a stop, very shortly after the Cat Converter Overtemp indictator (from TTS Datamaster) indicates CCOT and fuel mixture goes to the rich limit (12.7 or so as per PCM program), around 0.92v.

What I have noticed if I change that to leaner, say 14.7, it will go to 0.7v, but it stays in CCOT much longer. So somehow it thinks the converters are too hot. Even when coolant temps are cold, say 5 min from cold start in 0F weather, it will do it. It seems it is a ratio of time from the acceleration (like a certain MAP pressure exceeded) and then a multiplier of time from that time over that MAP. Say 3 seconds over that MAP value it might cool the converter for 9 seconds, etc. Not sure yet.