Stock 996 Fuel tank ventilation and catalytic converter readiness FAIL
08-13-2018, 09:51 PM
#1
Rennlist Member
Thread Starter
Stock 996 Fuel tank ventilation and catalytic converter readiness FAIL
So I sold my 2003 C2 to my Dad. He took it for an emissions test today and the testing center said they could not communicate with the catalytic converter readiness via the OBDII port so it failed the test. He drove the car for maybe 45 minutes before the test so it was plenty warm. The car shows no CEL and runs great. I put my Durametric on it tonight and it shows NO fault codes but under the systems test section it shows "Fuel Tank Ventilation - Fail" and "Catalytic Converter Readiness - Fail" The car is all stock...stock exhaust, stock ECU tune, and has a new gas cap within the last year (due to the retaining cord breaking off). Any suggestions on the cause...has anyone had this problem? I did a search and most of the posts on this are people with ECU performance tunes but this car is all stock.
08-13-2018, 10:44 PM
#2
The readiness fail is not necessarily a fault. It means that the car probably had codes cleared recently and that particular metric hasn't had enough data to become "ready". Driving it more will eventually change the status to "ready" or "error". I don't know about the fuel ventilation failure.
08-13-2018, 10:55 PM
#3
Burning Brakes
This question requires a long technical answer. Rather than trying to explain it. Being a mechanic i can tell you it is a pain in the a$$ to get the monitors to change from "failed or not ready" to "complete". Here is a copy and paste from the internet.
Why is a monitor incomplete or “not ready”
Clearing the diagnostic trouble codes (DTCs) and the Check Engine Light will reset the monitor statuses too. This typically occurs during or after vehicle repair.
Statuses are also reset in case of power failure. This usually happens when the battery has been disconnected. That’s why it is not advisable to disconnect the battery. If you need to disconnect the battery for example to replace it, read further. You will learn how to get the monitors back to complete.
For the current monitoring cycle, or “this drive cycle”, the status is set to incomplete upon starting a new monitoring cycle. It is a normal situation for these monitors to be incomplete when starting the engine.
Depending on your country and state, OBDII vehicle may not pass the annual inspection unless the required monitors since reset are complete. For example, the US Environmental Protection Agency guidelines allow up to two monitors to be not readyfor model year 1996 through 2000 vehicles. For 2001 and newer model year vehicles only single monitor status can be incomplete or not ready.
How to get the monitors complete or “ready”?
Because the monitors are self check routines, the best way to get them ready is to drive the car. Yet, monotonic driving will not most likely meet all the needed conditions. That’s why there is so called OBD drive cycle. But before going into that, let’s go through the obvious ones.
First, make sure that the MIL (Malfunction Indicator Light) is not commanded on. Having stored or even pending diagnostic trouble codes active may prevent a monitor from running to completion.
Second, make sure that you have enough fuel in the car. Some monitors, for instance the EVAP monitor, may require the fuel level to be between 35% and 85% to initiate the diagnostic testing.
Third, complete the so called “drive cycle”. About one week of combined city and highway driving is usually enough to allow the monitors to reach complete status. The drive cycle is explained in more details in the next paragraph.
OBD drive cycle
The purpose of the OBD2 drive cycle is to let your car run on-board diagnostics. This, in turn, allows the readiness monitors to operate. And detect potential malfunctions of your car’s emission system. The correct drive cycle for your car can vary greatly depending on the car model and manufacturer. Also, the monitor in question affects the required drive cycle.
Today, many vehicle manufacturers include these drive cycles in the vehicle owner’s manual. Typically, a few days of normal driving, both city and highway, will make the monitors ready. The following generic drive cycle can be used as a guideline if a specific drive cycle is not known. It will assist with resetting monitors when a car specific drive cycle is not available. However, it may not work for all cars and monitors.
The drive cycle can be difficult to follow exactly under normal driving conditions. Thus, it is better to drive it in restricted area!
The universal OBD-II drive cycle begins with a cold start. You should have coolant temperature below 50 C/122 F, and the coolant and air temperatures within 11 degrees of one another. This condition can be achieved by letting the car to sit overnight.
The ignition key must not be left ON position before the cold start. Otherwise the heated oxygen sensor diagnostic may not run.
Start the engine and idle the engine in drive for two and half minutes, with the A/C and rear defroster on if equipped.
Turn the A/C and rear defroster off, and speed up to 90 km/h (55 mph) under moderate, constant acceleration. Hold at a steady speed for three minutes.
Slow down to 30 km/h (20 mph) without braking. Do not depress the clutch if you are running with manual transmission.
Speed up back to 90-100 km/h (55-60 mph) at 3/4 throttle. Hold at a steady speed for five minutes.
Slow down to a stop without braking.
Why is a monitor incomplete or “not ready”
Clearing the diagnostic trouble codes (DTCs) and the Check Engine Light will reset the monitor statuses too. This typically occurs during or after vehicle repair.
Statuses are also reset in case of power failure. This usually happens when the battery has been disconnected. That’s why it is not advisable to disconnect the battery. If you need to disconnect the battery for example to replace it, read further. You will learn how to get the monitors back to complete.
For the current monitoring cycle, or “this drive cycle”, the status is set to incomplete upon starting a new monitoring cycle. It is a normal situation for these monitors to be incomplete when starting the engine.
Depending on your country and state, OBDII vehicle may not pass the annual inspection unless the required monitors since reset are complete. For example, the US Environmental Protection Agency guidelines allow up to two monitors to be not readyfor model year 1996 through 2000 vehicles. For 2001 and newer model year vehicles only single monitor status can be incomplete or not ready.
How to get the monitors complete or “ready”?
Because the monitors are self check routines, the best way to get them ready is to drive the car. Yet, monotonic driving will not most likely meet all the needed conditions. That’s why there is so called OBD drive cycle. But before going into that, let’s go through the obvious ones.
First, make sure that the MIL (Malfunction Indicator Light) is not commanded on. Having stored or even pending diagnostic trouble codes active may prevent a monitor from running to completion.
Second, make sure that you have enough fuel in the car. Some monitors, for instance the EVAP monitor, may require the fuel level to be between 35% and 85% to initiate the diagnostic testing.
Third, complete the so called “drive cycle”. About one week of combined city and highway driving is usually enough to allow the monitors to reach complete status. The drive cycle is explained in more details in the next paragraph.
OBD drive cycle
The purpose of the OBD2 drive cycle is to let your car run on-board diagnostics. This, in turn, allows the readiness monitors to operate. And detect potential malfunctions of your car’s emission system. The correct drive cycle for your car can vary greatly depending on the car model and manufacturer. Also, the monitor in question affects the required drive cycle.
Today, many vehicle manufacturers include these drive cycles in the vehicle owner’s manual. Typically, a few days of normal driving, both city and highway, will make the monitors ready. The following generic drive cycle can be used as a guideline if a specific drive cycle is not known. It will assist with resetting monitors when a car specific drive cycle is not available. However, it may not work for all cars and monitors.
The drive cycle can be difficult to follow exactly under normal driving conditions. Thus, it is better to drive it in restricted area!
The universal OBD-II drive cycle begins with a cold start. You should have coolant temperature below 50 C/122 F, and the coolant and air temperatures within 11 degrees of one another. This condition can be achieved by letting the car to sit overnight.
The ignition key must not be left ON position before the cold start. Otherwise the heated oxygen sensor diagnostic may not run.
Start the engine and idle the engine in drive for two and half minutes, with the A/C and rear defroster on if equipped.
Turn the A/C and rear defroster off, and speed up to 90 km/h (55 mph) under moderate, constant acceleration. Hold at a steady speed for three minutes.
Slow down to 30 km/h (20 mph) without braking. Do not depress the clutch if you are running with manual transmission.
Speed up back to 90-100 km/h (55-60 mph) at 3/4 throttle. Hold at a steady speed for five minutes.
Slow down to a stop without braking.
08-14-2018, 12:01 AM
#4
Burning Brakes
Nick,
If cat efficiency is the problem, then it will probably not work itself out. Sounds like O2 and heaters are set? I would use Durametric and check the O2 upstream and downstream voltages, banks 1 and 2, to see if the downstream voltages are steady around 0.68-0.72v. This is assuming the upstream voltages follow the typical sign wave. If the downstream voltages are not rock steady (i.e., downstream following upstream sine wave), then the cat may be faulty. Have an idle problem also? You didn’t mention an aging O2 code, so O2s might be ok.
If you can make the downstream voltages steady, you will probably be able to get the cat efficiency readiness code to set. Then the evap will also set.
If cat efficiency is the problem, then it will probably not work itself out. Sounds like O2 and heaters are set? I would use Durametric and check the O2 upstream and downstream voltages, banks 1 and 2, to see if the downstream voltages are steady around 0.68-0.72v. This is assuming the upstream voltages follow the typical sign wave. If the downstream voltages are not rock steady (i.e., downstream following upstream sine wave), then the cat may be faulty. Have an idle problem also? You didn’t mention an aging O2 code, so O2s might be ok.
If you can make the downstream voltages steady, you will probably be able to get the cat efficiency readiness code to set. Then the evap will also set.
08-14-2018, 12:11 AM
#5
The evap test will only set when you idle the engine at the right condition. The cat readiness will be set ONLY after BOTH of the cats have passed the tests. It becomes complicated when one or both cats are marginal. The reason is the tests for both cats will run ONLY when you do a cold start and keep driving. If one of the cat tests failed, the DME will try the next cold start (i.e., most likely the next day for most). If it fails during one drive cycle, it doesn't matter how much more/longer you drive the car, the test will not run again (until the next cold start and drive). If the cats are marginal, these tests could also pass or fail randomly so it becomes a stochastic process of how long before you get both the cats passed the tests.
If you want to encourage the evap test and cat tests, start with a cold engine and idle for 2.5 minutes. Then start driving and try to keep the rev below 3k and speed below 60mph as much as possible traffic allowed. Steady speed as much as possible. Best is to drive local roads with 45mph speed limit for 10-15 min, then get on the freeway (drive at around 60mph or below) for a 3~4 miles, then park the car and keep the engine running for a few minutes (evap should then set). If both cats are healthy, the above should trigger the cat tests for both banks and the flag should set quickly.
If you want to encourage the evap test and cat tests, start with a cold engine and idle for 2.5 minutes. Then start driving and try to keep the rev below 3k and speed below 60mph as much as possible traffic allowed. Steady speed as much as possible. Best is to drive local roads with 45mph speed limit for 10-15 min, then get on the freeway (drive at around 60mph or below) for a 3~4 miles, then park the car and keep the engine running for a few minutes (evap should then set). If both cats are healthy, the above should trigger the cat tests for both banks and the flag should set quickly.
08-14-2018, 06:59 AM
#6
Drifting
Join Date: Sep 2011
Location: Ephrata, PA, USA now. Originally from the UK
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I have only had a completed evap one time in my 7 years of owning my 1999 car. Due to the fact that I am allowed 2 system fails and only have the one (evap system) fail to complete itself, I don't worry and drive the car normally. I have tried all ends up as ASHAI advices, to make the full complete with the evap but fail every time. The car runs great and ticks over at between 7 and 8 hundred at stand still and that is fine by me. .
08-14-2018, 11:23 AM
#7
Rennlist Member
Thread Starter
Thanks guys I will have him try the OBD drive cycle and see if it clears. I did have the battery disconnected for several days recently for various work on the car and I ran a code clear with my Durametric after reconnecting so it would make sense that it needs a drive cycle to clear.
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08-14-2018, 12:22 PM
#8
Once you get the Catalytic Converter to a ready status you should be good to go. The fuel evap issue will probably not show up.
https://www.colorado.gov/pacific/cdp...ed-information
"All OBD-inspected vehicles must have the Catalytic Converter, Oxygen Sensor, and Heated Oxygen Sensor (if so equipped) monitors set to “Ready” during the inspection. Vehicles model year 2000 and older can have two remaining monitors “Not Ready” while vehicles 2001 and newer can only have one unset monitor."
https://www.colorado.gov/pacific/cdp...ed-information
"All OBD-inspected vehicles must have the Catalytic Converter, Oxygen Sensor, and Heated Oxygen Sensor (if so equipped) monitors set to “Ready” during the inspection. Vehicles model year 2000 and older can have two remaining monitors “Not Ready” while vehicles 2001 and newer can only have one unset monitor."
