After fix, should I run until check engine clears itself or pro-actively clear codes?

Alfman45

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Jersey City, NJ
2005 Rubicon. I pulled 2 codes, P421 and P431, indicating Pre-cats are toast and/or leaking.
1st Step: They were loose at the manifold flange, so i took an impact wrench snugged up a bit more thinking it would solve the issue...it didnt and CEL came back on after a drive cycle.
2nd Step: Remove and inspect the pre-cats. Looked inside and all the catalyst material was gone. Also, downstream O2 sensors were damaged (presumably by the catalyst blowing by). I replaced the whole system, including 2 O2s, Precats, Cat and Muffler, as the cat back section was shot.

My goal is to pass NJ inspection. I didn't clear my CEL purposely: My thought is if I fixed it, CEL should go off eventually and indicate the job is done, instead of wondering whether i ran thru a full drive cycle. My question is CAN THIS TYPE OF CODE CLEAR ON ITS OWN? if it does clear after the drive cycle, can i take it straight to inspection or will the code still be in the system and trigger failure?

Let me know if this is enough info. Thanks!!
 
I see no reason to not clear the code. If the CEL comes back, then you immediately know the problem isn't fixed.

FWIW, last summer, just before renewal, I had a CEL for a small evap leak that I couldn't easily find and I didn't have time to really dig into it. I cleared the code while in line at the emissions test facility, passed, and had the CEL come back on the way home.
 
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If you're trying to get the car inspected. I would clear the CEL. Do the drive cycle so all the emission control set. Then go down and have it inspected.

The check engine light should go off onits own. "should" being the keyword. If you reset the codes you know it's off.
 
I see no reason to not clear the code. If the CEL comes back, then you immediately know the problem isn't fixed.

FWIW, last summer, just before renewal, I had a CEL for a small evap leak that I couldn't easily find and I didn't have time to really dig into it. I cleared the code while in line at the emissions test facility, passed, and had the CEL come back on the way home.
You are lucky. In Arizona the test emission status readiness. If you clear the computer it needs a drive cycle to set everything. There is an exception to this. I think we are allowed one status in not ready.

I cannot remember which one it is. But it requires the outside air temperature to be below a certain degree that never gets there in Arizona during the summer. So it can take months for it to set.
 
You are lucky. In Arizona the test emission status readiness. If you clear the computer it needs a drive cycle to set everything. There is an exception to this. I think we are allowed one status in not ready.

I cannot remember which one it is. But it requires the outside air temperature to be below a certain degree that never gets there in Arizona during the summer. So it can take months for it to set.
There may have been a sign at the entrance requiring me to keep the engine running and fully warmed. They didn't notice me shutting down to do the reset.

Then there was that one year I showed up with the half doors on. The guy told me to keep the windows rolled down and the doors unlocked. I reached out, patted the canvas and nodded. The guy laughed with embarrassment.

No one pays attention out here. :)
 
Most states that perform smog system tests will also verify that everything in the smog system is 'ready'. That takes driving the Jeep enough so the smog system will set those statuses to ready once enough engine starts and cold-warm-cold cycles have been completed. I'd reset the CELs by disconnecting the battery's negative cable for 3-5 minutes to verify if your fix actually fixed anything but realize that if NJ checks for those 'ready' statuses that your system won't be ready for a while. 40 cold-warm-cold cycles rings a bell for insuring everything is ready for the smog system test.
 
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This is the procedure to set emissions readiness.

@Jerry Bransford you can do it in 2. There is no set number of cold warm cycles. If you are just driving normally it may take that many to check off the conditions that must be met to trigger readiness.

Step One: How to Prepare Your Vehicle

  • Have the fuel tank between 30 and 70 percent full. Some systems, especially the EVAP system, need to have a specific level of fuel in order for the tests to be trusted. If the fuel tank is near empty or completely full, many of the basic tests will not run at all.
  • The vehicle must also have a good alternator and a strong battery. If you have to occasionally jump-start your vehicle, all of the memory from the powertrain control module (PCM) is erased, which includes the data that accurately tracks the results from various stages of the Drive Cycle. Also, if the battery is weak or undercharged, some of the most important tests will never run.
  • The vehicle must sit overnight, or for at least eight hours, in an environment that is less than 90° F. The engine temperature needs to match the air temperature in order to establish an accurate baseline for the testing. If the outside temperature is over 90° F, the fuel is too volatile and the EVAP system won't even try to run its tests, though some of the other emissions systems may run their tests.
  • The keys must be out of the ignition and all of the doors must be closed while the vehicle sits over night because many of the onboard computers "boot up" when the keys are in the ignition. Also, many of the onboard computers still run until all of the doors are closed after the vehicle is shut off and the keys are removed.
Step Two: The Cold Start

  • Start the vehicle and let it idle for two to three minutes in Park or Neutral. While it is idling, turn on the head lights, heater/defroster, and rear defroster for a three to five minute warm-up phase. Let the idle speed settle down to near the normal speed.
  • Next, put the vehicle in gear and drive through city streets at about 25 mph. Go up to about 35 to 40 mph a few times before slowing down to stop. Don't roll through the stop; be sure the car is really stopped, just like you learned in driving school. Accelerate from each stop in a normal fashion—not overly conservative, but not like you are competing in a drag race either.
Step Three: A Short Freeway Trip

  • After the vehicle has been cold started and driven for a few miles on city streets, the next step is to take it on a short freeway trip.
  • Enter the freeway on-ramp and allow enough room with respect to other vehicles so that you can do a 1/2 to 3/4 throttle acceleration up to freeway speed.
  • When you have accelerated up to around 60 mph and have safely merged into the flow of traffic, stay in the slow lane and maintain a steady speed of 55 to 60 mph for a minimum of five miles. Please use the cruise control to help you maintain speed.
  • Find a nice, long off ramp to exit from the freeway. As you exit, take your foot off of the accelerator and let the vehicle coast down until it stops under its own power as you complete your exit from the freeway. Do not use the foot brake and do not shift gears until the very end of this "coast down" phase.
Step Four: More City Driving

  • After you have completed the freeway trip, drive through the city streets for a repeat of the second part of Step Two.
  • Go up to about 35 to 40 mph a few times and then maintain a city speed of 25 mph before slowing down to stop. Again, don't roll through the stop and make sure to accelerate normally.
  • Pull in to a parking place and let the engine idle for one to two minutes and then shut it off.
Step Five: Have your Readiness Monitors Checked and Verified

  • Drive your vehicle to your regular shop and have them re-check your readiness monitors, present codes, and pending codes. They should do this as a courtesy and for free.
  • If all of your monitors are "ready" and there are no present or pending codes, then your vehicle has been properly repaired and is ready for an emissions inspection and for normal driving.
  • If your monitors are not ready, please click here for more information.
 
That's not an official or even a Jeep-specific procedure, it's just something that Repairpal.com came up with that may or may not work depending on the issue(s).
 
You are lucky. In Arizona the test emission status readiness. If you clear the computer it needs a drive cycle to set everything. There is an exception to this. I think we are allowed one status in not ready.

Georgia is the same, as long as 6 of the 7 systems shows ready they can test.
 
That's not an official or even a Jeep-specific procedure, it's just something that Repairpal.com came up with that may or may not work depending on the issue(s).
I have used this procedure on every vehicle I have ever owned (obd2). I have always been able to get my emissions readiness set quickly.

Well you might not like where the source comes from it does work and it works every time. All OBD2 is standard. It has a procedure. With the exception of Volkswagen that makes up their own rules like turning off when not connected to the smog tester.
 
Then there was that one year I showed up with the half doors on. The guy told me to keep the windows rolled down and the doors unlocked. I reached out, patted the canvas and nodded. The guy laughed with embarrassment.

No one pays attention out here. :)

This year I did mine with no doors or top, the guy performing the test seemed to really enjoy hanging his feet out of the door with one arm up on the back of the seat. Really made himself comfortable.
 
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FWIW - the "40-50 drive cycles over 400-500 miles" re-set is for the adaptive memory, not OBDII emissions test readiness. Disconnecting the battery for a period of time will clear DTC codes but does not clear the adaptive memory.

The procedure detailed by @Boinked is standard for all OBDII vehicles and should work on all OBDII jeeps. Generally speaking all one usually needs to do is warm up the vehicle after it has been sitting overnight by letting it idle for several minutes, do some normal city driving, then cruise on the freeway in the slow lane at a steady speed for 5-10 miles, then take city streets home.

My OBDII scan tool tests for smog check readiness and has always signaled ready after I have done this.
 
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In California all monitors must report READY with the exception of EVAP, it is the only one allowed to be NOT READY and still pass the smog test.
 
Wow. In PA emission tests are only required in certain counties (most, but not all). My county does not require them, but the next county does. The test is basically a sniff of your gas cap, and $40.
 
UPDATE:
1) I used a combination of procedures: The procedure outlined by Boinked and this one below.
https://www.wranglerforum.com/f210/...ncomplete-1046209.html#/topics/1046209?page=3
2) I stuck with my gut and kept the CEL on until it naturally cleared
3) CEL cleared after 3 cold starts (8 hours apart) and running all procedures for O2 and Catalyst sensors many many times over about 100 miles
4) PASSED NJ INSPECTION with all monitors!!! No worries until 2020

Thanks ALL!!
 
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UPDATE:
1) I used a combination of procedures: The procedure outlined by Boinked and this one below.
https://*********************/f210/...ncomplete-1046209.html#/topics/1046209?page=3
2) I stuck with my gut and kept the CEL on until it naturally cleared
3) CEL cleared after 3 cold starts (8 hours apart) and running all procedures for O2 and Catalyst sensors many many times over about 100 miles
4) PASSED NJ INSPECTION with all monitors!!! No worries until 2020

Thanks ALL!!

Was this the solution? If so, it's worthy of it's own "how-to" thread, so let me know!



__________________________________________________ __


UPSTREAM HO2S MONITOR DRIVE CYCLE INSTRUCTIONS

  • Do not turn off the ignition switch during the test procedure.
  • All Onboard System Readiness codes are cleared if the battery is disconnected or when the Powertrain Control Module (PCM) is cleared with the scan tool.
  • This drive cycle can be used to determine if the Readiness code for this Monitor will run and complete, and if the Malfunction Indicator Lamp (MIL) will remain off after the vehicle is driven.
  • Operating Ranges: Whenever a range of values is provided, try to operate the vehicle in the middle of the range. For example, if the vehicle speed range is from 45-65 MPH, operate the vehicle at as close as possible to 55 mph. If the Short Term fuel trim range is -20% to +20%; try to operate the vehicle near 0%.
  • Scan Tool Data: There are certain Parameter Identification (PID) values that must be within range before this Monitor will "run". It can be helpful to pull up those PID items on the scan tool so an assistant can view them during the test.
  • This information is a representation of a Drive Cycle, and may vary due to software revisions to the PCM.

UPSTREAM HO2S MONITOR PRETEST CONDITIONS
  • MIL is off.
  • No emission related diagnostic trouble codes (DTC's) are present.
  • BTS signal between 21-130ºF.
  • ECT signal from 147-260ºF.
  • Open Throttle Time from 1.0-13.9 minutes.
  • VSS signal between 10-100 MPH.

UPSTREAM HO2S MONITOR ENABLING CONDITIONS
  • Adaptive Cell ID number between 0.0 and 20.0.
  • Exhaust Time from 1.1-13.9 minutes.
  • Engine speed range between 448-992 RPM.
  • Maximum Test Time between 0-1.6 minutes.
  • VSS range between 0-5 MPH.

TEST PROCEDURE

  1. Connect the scan tool to the data link connector (DLC), and bring up the Readiness code for the Upstream Heated Oxygen Sensor (HO2S) Monitor.
  2. Start the engine and allow it run until the engine coolant is more than 147ºF.
  3. Drive at low vehicle speed at between 448-992 RPM for several minutes. Bring the vehicle to a stop, and allow the engine to run at idle speed for 1-2 minutes in Drive (in Neutral on models with a manual transmission).
  4. Check the status of the Readiness code for the Upstream HO2S Monitor. It should change to YES or COMPLETE when the test is done. If it does, return to the service bay and turn off the ignition key. If it does not, check for any temporary codes. If no temporary codes are set, return to step 1 and repeat the test procedure.

Notes

Adaptive Cell Number:
The cell the engine must reach before this Monitor will run.
Exhaust Time:
Once the PCM infers that the Exhaust system components have reached a specific temperature, a timer starts to turn (this is a calculated value).
MAX Test Time:
The maximum amount of time allowed for this Monitor.
Open Throttle Time:
The amount of time the vehicle is driven with the throttle open required in order to allow the oxygen sensors and catalytic converters to fully warm up. This parameter is generally used in relation to vehicle speed.


__________________________________________________ ___



HO2S HEATER MONITOR DRIVE CYCLE INSTRUCTIONS
  • Do not turn off the ignition switch during the test procedure.
  • All Onboard System Readiness codes are cleared if the battery is disconnected or when the Powertrain Control Module (PCM) is cleared with the scan tool.
  • This drive cycle can be used to determine if the Readiness code for this Monitor will run and complete, and if the Malfunction Indicator Lamp (MIL) will remain off after the vehicle is driven.
  • Operating Ranges: Whenever a range of values is provided, try to operate the vehicle in the middle of the range. For example, if the vehicle speed range is from 45-65 MPH, operate the vehicle at as close as possible to 55 mph. If the Short Term fuel trim range is -20% to +20%; try to operate the vehicle near 0%.
  • Scan Tool Data: There are certain Parameter Identification (PID) values that must be within range before this Monitor will "run". It can be helpful to pull up those PID items on the scan tool so an assistant can view them during the test.
  • This information is a representation of a Drive Cycle, and may vary due to software revisions to the PCM.

HO2S HEATER MONITOR PRETEST CONDITIONS
  • Engine cool-down period completed (requires a key-off period of 8 hours).
  • MIL is off.
  • No emission related diagnostic trouble codes (DTC's) are present.
  • ECT signal between -50ºF and 104ºF at startup.
  • ECT and BTS signals within 14.4ºF (8ºC) of the each other at startup.
  • HO2S-12 (Bank 1 Sensor 2) signal between 4.0-5.0v.
  • HO2S-22 (Bank 2 Sensor 2) signal between 4.0-5.0v.

HO2S HEATER MONITOR ENABLING CONDITIONS
  • Battery voltage from 10.5-15.0v.

TEST PROCEDURE
  1. Connect the scan tool to the data link connector (DLC), and bring up the Readiness code for the HO2S Heater Monitor.
  2. Start the engine (cold) and allow it to run at idle speed for 40-60 seconds.
  3. Bring the vehicle to a stop in a safe place, but do not turn off the ignition key.
  4. Check the status of the Readiness code for the HO2S Heater Monitor. It should change to YES or COMPLETE when the test is done. If it does, return to the service bay and turn off the ignition key. If it does not, check for any temporary codes. If no temporary codes are set, return to step 2 and repeat the test procedure.

Notes

ECT/BTS Range:
The ECT sensor and BTS sensors must be within a specific range of each other at engine startup in order for this Monitor to run.


__________________________________________________ ____



CATALYST MONITOR DRIVE CYCLE INSTRUCTIONS
  • Do not turn off the ignition switch during the test procedure.
  • All Onboard System Readiness codes are cleared if the battery is disconnected or when the Powertrain Control Module (PCM) is cleared with the scan tool.
  • This drive cycle can be used to determine if the Readiness code for this Monitor will run and complete, and if the Malfunction Indicator Lamp (MIL) will remain off after the vehicle is driven.
  • Operating Ranges: Whenever a range of values is provided, try to operate the vehicle in the middle of the range. For example, if the vehicle speed range is from 45-65 MPH, operate the vehicle at as close as possible to 55 mph. If the Short Term fuel trim range is -20% to +20%; try to operate the vehicle near 0%.
  • Scan Tool Data: There are certain Parameter Identification (PID) values that must be within range before this Monitor will "run". It can be helpful to pull up those PID items on the scan tool so an assistant can view them during the test.
  • This information is a representation of a Drive Cycle, and may vary due to software revisions to the PCM.

CATALYST MONITOR PRETEST CONDITIONS
  • MIL is off.
  • No emission related diagnostic trouble codes (DTC's) are present.
  • BTS signal range from 21-130ºF.
  • Catalyst temperature range from 0-2,040ºF.
  • ECT signal from 147-260ºF.
  • Open Throttle Time from 3.0-13.9 minutes.
  • VSS Range from 45-100 mph.
  • VSS MPH Time between 1 and 100 minutes.

CATALYST MONITOR ENABLING CONDITIONS
  • Catalyst temperature range from 0-2,040ºF.
  • Engine speed range from 1, 344-2,048 RPM.
  • Exhaust time from 3.0-13.9 minutes.
  • MAP signal from 12-30" Hg.
  • Minimum Test Time from 0.3-13.9 minutes.
  • VSS range from 50-65 MPH.

TEST PROCEDURE
  1. Connect the scan tool to the data link connector (DLC), and bring up the Readiness code for the Catalyst Monitor.
  2. Start the engine and allow it to idle until the ECT PID is more than 147ºF.
  3. Accelerate at part-throttle to 50-65 mph at an engine speed of 1,344-2,048 rpm with the MAP PID from 12-30" Hg in Drive (in 4th gear on models with a manual transmission) for several minutes. Bring the vehicle to a stop in a safe place, but do not turn off the ignition key.
  4. Check the status of the Readiness code for the Catalyst Monitor. It should change to YES or COMPLETE when the test is done. If it does, return to the service bay and turn off the ignition key. If it does not, check for any temporary codes. If no temporary codes are set, return to step 1 and repeat the test procedure.

Notes

Catalyst Temperature:
A calculated value based on ambient temperature, load, road speed, Short and Long Term fuel trim, spark advance, run time, and ECT sensor inputs.
Exhaust Time:
Once the PCM infers that the Exhaust system components have reached a specific temperature, a timer starts to turn (this is a calculated value).
MIN Run Time:
Minimum amount of time the engine has been running since startup. The numbers to the right of the decimal are tenths of a minute (e.g., 1.5 is equal to 1 minute and 30 seconds)
Open Throttle Time:
The amount of time the vehicle is driven with the throttle open required in order to allow the oxygen sensors and catalytic converters to fully warm up. This parameter is generally used in relation to vehicle speed.
 
Most states that perform smog system tests will also verify that everything in the smog system is 'ready'. That takes driving the Jeep enough so the smog system will set those statuses to ready once enough engine starts and cold-warm-cold cycles have been completed. I'd reset the CELs by disconnecting the battery's negative cable for 3-5 minutes to verify if your fix actually fixed anything but realize that if NJ checks for those 'ready' statuses that your system won't be ready for a while. 40 cold-warm-cold cycles rings a bell for insuring everything is ready for the smog system test.

Yes, Jerry is absolutely correct. In NJ you will be failed and they won't even test your vehicle any further if you've just cleared your codes and it doesn't have the 7 readys in the ECM.
 
Combination of both were the solution for fixing codes P0421 and P0431:
  • If loose, try to snug bolts that attach pre-cats to the manifold
  • Run a drive cycle to confirm if that worked (which it didnt for mine)
  • If not do the following:
    • Replace the Pre-cats, O2 downstream for both banks (if damaged like mine) and cat converter
      • Run thru drive cycle
        • OBD2 standard procedure posted by Boink
        • Procedure you reposted from the link
    • Dont reset the computer and wait for the CEL to clear on its own.
    • Pass Inspection!