yabadaba

Hi guys, I've only recently got HPTuners and one of the first things I've done is to check for diagnostic codes, even though no warning lights show on my dash display. It took a while for all the tests to complete, but eventually they did.

Here are the codes that appear. Anything to worry about?

[PCM] P0420 - Catalyst System Low Efficiency (Old) (History) (Immature)
[Brake] U1000 - Class 2 Communication Malfunction (History)
[Restraints] U1000 - Class 2 Communication Malfunction (History) (Immature)
[Restraints] U1016 - Loss of Class 2 Communication with VCM (History) (Immature)
[HUD] U1000 - Class 2 Communication Malfunction (History) (Immature)

NB: Not sure what 'Old', 'History' and 'Immature' mean....at least not in this context.

yabadaba

Okay, I've now discovered that the U codes are to be expected following a read from or write to the PCM, but what about that P0420 code?

Two things that I don't understand are why doesn't it cause the SES light to come on and what do 'Old', 'History' and 'Immature' mean?

Dan Stewart

Catalyst Low Efficiency means the computer thinks that you have a bad cat. The "20" in the code indicates that it is Bank 1.

Unfortunately, this could mean a couple things:
1. Bad cat
2. Bad downstream sensor
3. Both

As for the SES light....does it come on when you first turn the key on (bulb test). If so, then that means that there are no "active" DTC's stored in the computer.

I haven't used HPTuners (mostly use PowerTuner), but it looks like the "Old" and "Immature" means that it was at one time a pending code that never made it to "active" status. I guess "History" means that they are stored previous codes.

Personally, I would clear the codes and wait until all the readiness tests complete then see what you have again.