Readiness Monitors
08-29-2018, 09:29 PM
#1
Readiness Monitors
I know this general topic has been discussed before, but was wondering if anyone has ideas about my circumstance. Trying to to pass smog in CA and the catalytic readiness monitor won't set. As it is a higher milles car (98,xxx), I did the following in the past thousand miles:
Spark plugs
Coils
02 sensors
200 cell cats
I'm not concerned with the visual and have always gotten 200 cell cats to set the monitors in my other cars. It's the only monitor not setting and I've done the driving 55mph for ~60 miles now. Still not setting. Getting to the point I am ready to sell it. Any ideas of what I can do, and can you force set them in the computer?
Spark plugs
Coils
02 sensors
200 cell cats
I'm not concerned with the visual and have always gotten 200 cell cats to set the monitors in my other cars. It's the only monitor not setting and I've done the driving 55mph for ~60 miles now. Still not setting. Getting to the point I am ready to sell it. Any ideas of what I can do, and can you force set them in the computer?
08-30-2018, 01:05 PM
#2
Rennlist Member
I know this general topic has been discussed before, but was wondering if anyone has ideas about my circumstance. Trying to to pass smog in CA and the catalytic readiness monitor won't set. As it is a higher milles car (98,xxx), I did the following in the past thousand miles:
Spark plugs
Coils
02 sensors
200 cell cats
I'm not concerned with the visual and have always gotten 200 cell cats to set the monitors in my other cars. It's the only monitor not setting and I've done the driving 55mph for ~60 miles now. Still not setting. Getting to the point I am ready to sell it. Any ideas of what I can do, and can you force set them in the computer?
Spark plugs
Coils
02 sensors
200 cell cats
I'm not concerned with the visual and have always gotten 200 cell cats to set the monitors in my other cars. It's the only monitor not setting and I've done the driving 55mph for ~60 miles now. Still not setting. Getting to the point I am ready to sell it. Any ideas of what I can do, and can you force set them in the computer?
If battery disconnect, try the drive cycle up to 2 times before giving up and selling.
08-31-2018, 11:04 AM
#5
PorscheG96 made extremely an helpful thread on this, see here: https://rennlist.com/forums/996-gt2-...ted-cel-s.html
Relevant snippet below.
Relevant snippet below.
When the engine is first started it's running in open loop mode, ie. the O2 sensors are skipped in favor of a rich ECU map. Once the engine reaches a certain temperature then the ECU enters closed loop operation and the O2 sensor + O2 heater diagnostics are performed. When these tests pass then the next couple of tests are for the Secondary Air Injection and Evap Systems. It turns out that the secondary air injection test is performed at idle and this explained the unexpected idle surge that I noticed on my initial test drive. My warning to others out there who are shopping for GT3 or any OBDII Porsche is to bring an OBD scanner with you and check to see a) whether there are any stored fault codes and b) whether the smog monitors are properly set. I wish I'd made certain the the readiness monitors were all good before pulling the trigger on my purchase but I didn't know that the quick idle surge was a diagnostic test to ready the monitors. Apparently a mechanic had worked some voodoo to make it pass smog but it was shortly thereafter when the catalyst monitor failed and caused this entire headache.
Anyway, the final test is the catalyst which is the big one. I've seen various publications of drive cycle recommendations but I'll share what I did and maybe others can chime in with drive cycles that are faster and easier:
-At least 3 cold engine starts, so the cat readiness took me 3 days
-Drive several minutes between 25-29 mph under 2800 RPM
-Drive several minutes between 55-59 mph under 2800 RPM
-Drive several minutes between 25-29 mph under 2800 RPM
-Idle for 5 minutes
-Shut down and restart engine
-Repeat at step 2
I wasn't sure what the reasons were behind such mundane driving techniques until watching my OBD readouts for the O2 sensors. It turns out that the ECU performs several tests at constant speed & throttle operation so that the driver cannot manipulate the results. You can see in the following graph that the ECU goes to full lean on the fuel trim independently causing front O2 sensor voltages dip to reflect the lean condition. This is followed by the ECU going full rich as evidenced by the front O2 sensor plateaus which results in the rear O2 sensors slowly stepping from lean to rich again....
.... These tests are performed many, many times before the catalyst readiness is passed -- ultimately, it took 186 miles of mixed driving for my system to be ready.
Anyway, the final test is the catalyst which is the big one. I've seen various publications of drive cycle recommendations but I'll share what I did and maybe others can chime in with drive cycles that are faster and easier:
-At least 3 cold engine starts, so the cat readiness took me 3 days
-Drive several minutes between 25-29 mph under 2800 RPM
-Drive several minutes between 55-59 mph under 2800 RPM
-Drive several minutes between 25-29 mph under 2800 RPM
-Idle for 5 minutes
-Shut down and restart engine
-Repeat at step 2
I wasn't sure what the reasons were behind such mundane driving techniques until watching my OBD readouts for the O2 sensors. It turns out that the ECU performs several tests at constant speed & throttle operation so that the driver cannot manipulate the results. You can see in the following graph that the ECU goes to full lean on the fuel trim independently causing front O2 sensor voltages dip to reflect the lean condition. This is followed by the ECU going full rich as evidenced by the front O2 sensor plateaus which results in the rear O2 sensors slowly stepping from lean to rich again....
.... These tests are performed many, many times before the catalyst readiness is passed -- ultimately, it took 186 miles of mixed driving for my system to be ready.