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2001 Toyota Corolla Failed Inspection - Help!



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LOLRECONLOL

I had to get my Corolla inspected at the end of November and after waiting for around 2 hours, I found out it failed for emissions, and the codes that were "present" are P0171, P0446, and P1349. I had 45 days from then to get it inspected again, so I have a few weeks before I have to bring it back. Has anyone had these codes before? Is there any way I could fix them myself without biting a huge bill at the garage? If not, how much should I be prepared to pay? Thanks! default_smile

TheDarkKnight

Those codes look familiar - i think i had some of those...

Do a search, and you might find some good info.

As for a more intelligent/helpful reply, i will defer to fishexpo

good luck

tdk

P0171 - System Too Lean

P0446 - Evaporative Emmission Control System Vent Control Circuit Malfunction

P1349 - VVT System Malfunction

Unfortunately, it is impossible to tell if those were set all at the same time (be very unusual), and which was is first. I would reset the ECM to "clear" the codes and drive the car normally. See if the codes come back (CEL lamp will come back on). Have the car scanned to verify which code is being tripped. If all three are being set - could be a simple grounding issue up to wiring and ECM failure. Fortunately, these are well known and have several potential fixes - unfortunately, depending on where you bring the car to fix them - they will either charge you an arg + leg or make things worse (these are unique to the 1ZZ-FE engine - can be easy fixes if the shop knowns the engine well).

P0171 - most common cause is a dirty MAF sensor, cleaning this generally will fix this code.

P0446 - being a control circuit malfunction, means the probably could be anywhere - most of the time, this code goes away when you reset the ECM. If it comes back, you have to check all the electrical connections to the VSV's by the vapor canister (under the car, by the fuel tank). Also check the vent and vacuum lines under there. Generally - this will be set by some "hiccup" in the system. If everything looks OK, you'll need to to a "smoke" test of the emissions systems to check for leaks.

P1349 - is a little more complicated, this refers to some issue (electrical or mechanical) in the variable valve timing feature of the engine. Could be caused by any number of sources, most common are from oil deposits clogging up the actuator, which will lead to a clogged VVT oil control valve filter and/or oil control valve actuator. Both are on the front of the engine, right by the alternator.

LOLRECONLOL

P0171 - System Too Lean

 

P0446 - Evaporative Emmission Control System Vent Control Circuit Malfunction

P1349 - VVT System Malfunction

Unfortunately, it is impossible to tell if those were set all at the same time (be very unusual), and which was is first. I would reset the ECM to "clear" the codes and drive the car normally. See if the codes come back (CEL lamp will come back on). Have the car scanned to verify which code is being tripped. If all three are being set - could be a simple grounding issue up to wiring and ECM failure. Fortunately, these are well known and have several potential fixes - unfortunately, depending on where you bring the car to fix them - they will either charge you an arg + leg or make things worse (these are unique to the 1ZZ-FE engine - can be easy fixes if the shop knowns the engine well).

P0171 - most common cause is a dirty MAF sensor, cleaning this generally will fix this code.

P0446 - being a control circuit malfunction, means the probably could be anywhere - most of the time, this code goes away when you reset the ECM. If it comes back, you have to check all the electrical connections to the VSV's by the vapor canister (under the car, by the fuel tank). Also check the vent and vacuum lines under there. Generally - this will be set by some "hiccup" in the system. If everything looks OK, you'll need to to a "smoke" test of the emissions systems to check for leaks.

P1349 - is a little more complicated, this refers to some issue (electrical or mechanical) in the variable valve timing feature of the engine. Could be caused by any number of sources, most common are from oil deposits clogging up the actuator, which will lead to a clogged VVT oil control valve filter and/or oil control valve actuator. Both are on the front of the engine, right by the alternator.

Yikes! I haven't checked this in a little while, I've been busy. I have an update on the car - so I took it to the garage and they cleared the codes out and reset the system. They said to drive 100 miles and come back, and everything should be working. I ended up putting around 250 miles on it and brought it back, but now the error codes are gone and the system still hasn't reset itself so I can't get it re-inspected yet. I took it back to the garage yesterday, and he said put 100 more miles on it then bring it back. Is there anything I have to do in those 100 miles to make it reset, or is it just one of those things that can take a while? Because right now the way I'm doing it seems like it's a waste of mileage and money. Another thing is that my CEL isn't on, and the garages I've brought it to seem surprised by that (not sure if that's in a good or bad way) - I wish I knew how to work on cars. default_tongue

Basically, the garage is waiting for the OBD I/M readiness monitor to be set. When you clear the ECM, there are stored parameters that also get erased, and the car has to "relearn" those parameters. Some of those are learned very quickly, others - like the EVAP codes, can take a while to reset. The I/M readiness monitor - has to complete so many "drive cycles" before it enters a ready mode, before it hits those drive cycles, your emissions testing can not be done. There is no easy formula that you can follow to set the I/M readiness - though some have followed a universal guideline and it worked for them.

Example of that guideline is as follows:

- Start the engine, idle the engine in gear (automatic) or turn on accessories (manual) for 180 seconds

- Accelerate to 55 mph at 50% throttle

- Hold steady speed of 55 mph for 180 seconds

- Coast to 20 mph (no braking or depressing the clutch)

- Accelerate back to 55 to 60 mph at 75% throttle

- Hold steady speed of 55 to 60 mph for 300 seconds

- Coast down to a stop (without braking)

- Shutdown engine, wait 240 seconds, restart and repeat above

As you can - nearly impossible to accomplish those setups unless the car is on a dynometer, might be able to pull that off in more rural areas, but not in the city. Driving normally should hit all those conditions over the course of a few hundred miles, several days. The caveat is the speed, if you drive almost exclusively in the city - you may not hit the high speed threshold for setting the I/M readiness monitor. The flip side is driving almost exclusively highway - you may not hit the start/stop engine cycling, low speed, coast down threshold for setting the I/M readiness monitor. The trick is driving a few hundred miles of mixed city and highway with some periods of idling, startup/shutdown, varying the speed/engine load over a wide temperature range.

Sort of a PITA, as the actual emissions are probably quite clean - most states that do emissions testing only query the ECM's I/M readiness monitor. The car could be billowing smoke and raw fuel, but if the ECM's self test checks out OK - you pass. Some places run an I/M 240 emissions test - which involves querying the computer and running the car on a "treadmill" or dynometer over a prescribed course.

LOLRECONLOL

Basically, the garage is waiting for the OBD I/M readiness monitor to be set. When you clear the ECM, there are stored parameters that also get erased, and the car has to "relearn" those parameters. Some of those are learned very quickly, others - like the EVAP codes, can take a while to reset. The I/M readiness monitor - has to complete so many "drive cycles" before it enters a ready mode, before it hits those drive cycles, your emissions testing can not be done. There is no easy formula that you can follow to set the I/M readiness - though some have followed a universal guideline and it worked for them.

 

Example of that guideline is as follows:

- Start the engine, idle the engine in gear (automatic) or turn on accessories (manual) for 180 seconds

- Accelerate to 55 mph at 50% throttle

- Hold steady speed of 55 mph for 180 seconds

- Coast to 20 mph (no braking or depressing the clutch)

- Accelerate back to 55 to 60 mph at 75% throttle

- Hold steady speed of 55 to 60 mph for 300 seconds

- Coast down to a stop (without braking)

- Shutdown engine, wait 240 seconds, restart and repeat above

As you can - nearly impossible to accomplish those setups unless the car is on a dynometer, might be able to pull that off in more rural areas, but not in the city. Driving normally should hit all those conditions over the course of a few hundred miles, several days. The caveat is the speed, if you drive almost exclusively in the city - you may not hit the high speed threshold for setting the I/M readiness monitor. The flip side is driving almost exclusively highway - you may not hit the start/stop engine cycling, low speed, coast down threshold for setting the I/M readiness monitor. The trick is driving a few hundred miles of mixed city and highway with some periods of idling, startup/shutdown, varying the speed/engine load over a wide temperature range.

Sort of a PITA, as the actual emissions are probably quite clean - most states that do emissions testing only query the ECM's I/M readiness monitor. The car could be billowing smoke and raw fuel, but if the ECM's self test checks out OK - you pass. Some places run an I/M 240 emissions test - which involves querying the computer and running the car on a "treadmill" or dynometer over a prescribed course.

Thanks a lot! I was looking at some ways to reset it, and all of them were different so I loosely based my driving off this and just racked up the miles. I passed inspection and now I'm good for a few years. Thank you! default_smile