P0430
P0430 I just bought an 07 Express 2500 4.8 with 330k miles. Yes it was really cheap. Runs and drives great. CEL on and get code P0430 for bank 2 catalyst efficiency.
Used scan tool to watch 02 sensor voltages. Sensor 1 oscillates like it should, sensor 2 is all over the place. So looks like cat is bad, correct?
Checked bank 1 for the heck of it, and they look the same as bank 2. So why aren't I getting a code for this bank?
Also, with an infrared gun, bank 1 converter is 100 degrees cooler at the rear of converter than front, and bank 2 is opposite. Hotter at the rear, which seems like bank 2 converter is working??
Thanks for any help.
Used scan tool to watch 02 sensor voltages. Sensor 1 oscillates like it should, sensor 2 is all over the place. So looks like cat is bad, correct?
Checked bank 1 for the heck of it, and they look the same as bank 2. So why aren't I getting a code for this bank?
Also, with an infrared gun, bank 1 converter is 100 degrees cooler at the rear of converter than front, and bank 2 is opposite. Hotter at the rear, which seems like bank 2 converter is working??
Thanks for any help.
TECH Senior Member
Joined: Apr 2002
Posts: 6,080
Likes: 17
From: So.Cal.
P0420 and P0430
These are purely an indication of the efficiency of the catalysts, and requires NBO2's to be functioning in order to perform the test;
PCM tests for those DTC's like this, on each bank:
coming back down to idle (from a 55+ mph freeway blast), PCM drives a step in fueling, looks for this step to show up at front NBO2, and then looks for it to show up at rear NBO2... if the elapsed time for this event between front and rear is too short then a DTC is triggered for that bank;
( if you have a scantool with you, you will be able to see the fueling step and front/rear NBO2 responses if you know when the catalyst efficiency test activates )
some vehicles has asymmetric response time thresholds (different between banks).
These are purely an indication of the efficiency of the catalysts, and requires NBO2's to be functioning in order to perform the test;
PCM tests for those DTC's like this, on each bank:
coming back down to idle (from a 55+ mph freeway blast), PCM drives a step in fueling, looks for this step to show up at front NBO2, and then looks for it to show up at rear NBO2... if the elapsed time for this event between front and rear is too short then a DTC is triggered for that bank;
( if you have a scantool with you, you will be able to see the fueling step and front/rear NBO2 responses if you know when the catalyst efficiency test activates )
some vehicles has asymmetric response time thresholds (different between banks).
Thanks, but not exactly sure what you are saying. It may just be an 02 sensor? I have another set of 4 from an 03 6.0 express. Not sure if they are the same or not yet, but if they are, I should clear the code and try them? I cleared today, and came back on in about 10 miles.
TECH Senior Member
Joined: Apr 2002
Posts: 6,080
Likes: 17
From: So.Cal.
P0430 If the rear O2S have slow response then P0420/P0430 will never set.
If the catalyst is "worn out" and the rear O2S have fast response then P0420/P0430 will set.
i.e. the test uses the front/rear O2S to actively measure how quickly a fuel step propagates thru the cat, if it propagates too quickly the test fails (DTC sets);
what I'm saying is that quick responding front O2S and lazy responding rear O2S help to avoid failing.
Yes, whenever the test runs it will fail if the catalyst is worn out.
If the catalyst is "worn out" and the rear O2S have fast response then P0420/P0430 will set.
i.e. the test uses the front/rear O2S to actively measure how quickly a fuel step propagates thru the cat, if it propagates too quickly the test fails (DTC sets);
what I'm saying is that quick responding front O2S and lazy responding rear O2S help to avoid failing.
Yes, whenever the test runs it will fail if the catalyst is worn out.
