p0455 (EVAP) DTC questions

('04 Cavalier) has been setting a p0455 code. All the components seem
to be working, at least roughly:
- purge valve operates, and blocks/passes when I blow on it.
- vent valve, same.
- canister blows through. (ie, doesn't seem plugged)
- (I did change the gas cap.)

Alldata (supposedly the same as the Helm book) says the EVAP test is run
when ...
- The engine is running.
- ignition voltage is between 10-18 volts .
- barometric pressure (BARO) is more than 75 kPa.
- fuel level is between 15-85%.
- engine coolant temp (ECT) is between 4-30C (39-86F).
- intake air temp (IAT) is between 4-30C (39-86F).
- start-up ECT and AT are within 9C (16F) of each other.
- vehicle speed (VSS) is less than 121 km/h (75 mph) .

We should meet that every time we run, this time of year. Instead, it
usually takes multiple start/run cycles before the code sets ... AND,
according to our scan tool, the EVAP test HAS NOT BEEN RUN before that.
It's not that it sometimes passes: it says it hasn't been run. All the
other diagnostics have, but not EVAP.

Further confusing to me, when the test does run (and fails), the
freeze-frame data shows an engine temp of ~175F, every time. This is
consistent with where we are in the drive cycle - the engine is warm.
This seems to directly violate the ECT 39-86F rule.


I would appreciate any thoughts on any of the above.

Thank you.

On Fri, 23 May 2014 17:46:08 -0400, George >
wrote:

>('04 Cavalier) has been setting a p0455 code. All the components seem
>to be working, at least roughly:
> - purge valve operates, and blocks/passes when I blow on it.
> - vent valve, same.
> - canister blows through. (ie, doesn't seem plugged)
> - (I did change the gas cap.)
>
>Alldata (supposedly the same as the Helm book) says the EVAP test is run
>when ...
> - The engine is running.
> - ignition voltage is between 10-18 volts .
> - barometric pressure (BARO) is more than 75 kPa.
> - fuel level is between 15-85%.
> - engine coolant temp (ECT) is between 4-30C (39-86F).
> - intake air temp (IAT) is between 4-30C (39-86F).
> - start-up ECT and AT are within 9C (16F) of each other.
> - vehicle speed (VSS) is less than 121 km/h (75 mph) .
>
>We should meet that every time we run, this time of year. Instead, it
>usually takes multiple start/run cycles before the code sets ... AND,
>according to our scan tool, the EVAP test HAS NOT BEEN RUN before that.
>It's not that it sometimes passes: it says it hasn't been run. All the
>other diagnostics have, but not EVAP.
>
>Further confusing to me, when the test does run (and fails), the
>freeze-frame data shows an engine temp of ~175F, every time. This is
>consistent with where we are in the drive cycle - the engine is warm.
>This seems to directly violate the ECT 39-86F rule.

I could be wrong, but those parameters don't make sense. It's more
likely the test temp is 39-86C, not F. Some cars have more detailed
requirements, such as steady speed for X amount of time. This is a
difficult code for do-it-yourselfers.

On Fri, 23 May 2014 18:47:34 -0700, Bill Vanek >
wrote:

>On Fri, 23 May 2014 17:46:08 -0400, George >
>wrote:
>
>>('04 Cavalier) has been setting a p0455 code. All the components seem
>>to be working, at least roughly:
>> - purge valve operates, and blocks/passes when I blow on it.
>> - vent valve, same.
>> - canister blows through. (ie, doesn't seem plugged)
>> - (I did change the gas cap.)
>>
>>Alldata (supposedly the same as the Helm book) says the EVAP test is run
>>when ...
>> - The engine is running.
>> - ignition voltage is between 10-18 volts .
>> - barometric pressure (BARO) is more than 75 kPa.
>> - fuel level is between 15-85%.
>> - engine coolant temp (ECT) is between 4-30C (39-86F).
>> - intake air temp (IAT) is between 4-30C (39-86F).
>> - start-up ECT and AT are within 9C (16F) of each other.
>> - vehicle speed (VSS) is less than 121 km/h (75 mph) .
>>
>>We should meet that every time we run, this time of year. Instead, it
>>usually takes multiple start/run cycles before the code sets ... AND,
>>according to our scan tool, the EVAP test HAS NOT BEEN RUN before that.
>>It's not that it sometimes passes: it says it hasn't been run. All the
>>other diagnostics have, but not EVAP.
>>
>>Further confusing to me, when the test does run (and fails), the
>>freeze-frame data shows an engine temp of ~175F, every time. This is
>>consistent with where we are in the drive cycle - the engine is warm.
>>This seems to directly violate the ECT 39-86F rule.
>
>I could be wrong, but those parameters don't make sense. It's more
>likely the test temp is 39-86C, not F. Some cars have more detailed
>requirements, such as steady speed for X amount of time. This is a
>difficult code for do-it-yourselfers.

Well, this link shows similar criteria:

http://www.searchautoparts.com/sites...-docs/EVAP.pdf

And, it's not just the ECT itself: both that link and Alldata say the
IAT and ECT need to be close to each other. That would be kind of
uncomfortable at 86C. I'll test the 'constant speed' idea - almost all
of our driving is in the city.

> This is a difficult code for do-it-yourselfers.

Yeah. I may end up punting it. But, $$$.

On Sat, 24 May 2014 09:49:18 -0400, George >
wrote:

>On Fri, 23 May 2014 18:47:34 -0700, Bill Vanek >
>wrote:
>
>>On Fri, 23 May 2014 17:46:08 -0400, George >
>>wrote:
>>
>>>('04 Cavalier) has been setting a p0455 code. All the components seem
>>>to be working, at least roughly:
>>> - purge valve operates, and blocks/passes when I blow on it.
>>> - vent valve, same.
>>> - canister blows through. (ie, doesn't seem plugged)
>>> - (I did change the gas cap.)
>>>
>>>Alldata (supposedly the same as the Helm book) says the EVAP test is run
>>>when ...
>>> - The engine is running.
>>> - ignition voltage is between 10-18 volts .
>>> - barometric pressure (BARO) is more than 75 kPa.
>>> - fuel level is between 15-85%.
>>> - engine coolant temp (ECT) is between 4-30C (39-86F).
>>> - intake air temp (IAT) is between 4-30C (39-86F).
>>> - start-up ECT and AT are within 9C (16F) of each other.
>>> - vehicle speed (VSS) is less than 121 km/h (75 mph) .
>>>
>>>We should meet that every time we run, this time of year. Instead, it
>>>usually takes multiple start/run cycles before the code sets ... AND,
>>>according to our scan tool, the EVAP test HAS NOT BEEN RUN before that.
>>>It's not that it sometimes passes: it says it hasn't been run. All the
>>>other diagnostics have, but not EVAP.
>>>
>>>Further confusing to me, when the test does run (and fails), the
>>>freeze-frame data shows an engine temp of ~175F, every time. This is
>>>consistent with where we are in the drive cycle - the engine is warm.
>>>This seems to directly violate the ECT 39-86F rule.
>>
>>I could be wrong, but those parameters don't make sense. It's more
>>likely the test temp is 39-86C, not F. Some cars have more detailed
>>requirements, such as steady speed for X amount of time. This is a
>>difficult code for do-it-yourselfers.
>
>Well, this link shows similar criteria:
>
>http://www.searchautoparts.com/sites...-docs/EVAP.pdf
>
>And, it's not just the ECT itself: both that link and Alldata say the
>IAT and ECT need to be close to each other. That would be kind of
>uncomfortable at 86C. I'll test the 'constant speed' idea - almost all
>of our driving is in the city.
>
>> This is a difficult code for do-it-yourselfers.
>
>Yeah. I may end up punting it. But, $$$.

Okay, I see that now, but those are the startup temps, not the
conditions during which the test is run. In other words, if the temps
are outside of the required range when you start the car, the test
will not be run anytime during that drive cycle.

Bill Vanek wrote:
> On Sat, 24 May 2014 09:49:18 -0400, George >
> wrote:
>
>> On Fri, 23 May 2014 18:47:34 -0700, Bill Vanek >
>> wrote:
>>
>>> On Fri, 23 May 2014 17:46:08 -0400, George >
>>> wrote:
>>>
>>>> ('04 Cavalier) has been setting a p0455 code. All the components seem
>>>> to be working, at least roughly:
>>>> - purge valve operates, and blocks/passes when I blow on it.
>>>> - vent valve, same.
>>>> - canister blows through. (ie, doesn't seem plugged)
>>>> - (I did change the gas cap.)
>>>>
>>>> Alldata (supposedly the same as the Helm book) says the EVAP test is run
>>>> when ...
>>>> - The engine is running.
>>>> - ignition voltage is between 10-18 volts .
>>>> - barometric pressure (BARO) is more than 75 kPa.
>>>> - fuel level is between 15-85%.
>>>> - engine coolant temp (ECT) is between 4-30C (39-86F).
>>>> - intake air temp (IAT) is between 4-30C (39-86F).
>>>> - start-up ECT and AT are within 9C (16F) of each other.
>>>> - vehicle speed (VSS) is less than 121 km/h (75 mph) .
>>>>
>>>> We should meet that every time we run, this time of year. Instead, it
>>>> usually takes multiple start/run cycles before the code sets ... AND,
>>>> according to our scan tool, the EVAP test HAS NOT BEEN RUN before that.
>>>> It's not that it sometimes passes: it says it hasn't been run. All the
>>>> other diagnostics have, but not EVAP.
>>>>
>>>> Further confusing to me, when the test does run (and fails), the
>>>> freeze-frame data shows an engine temp of ~175F, every time. This is
>>>> consistent with where we are in the drive cycle - the engine is warm.
>>>> This seems to directly violate the ECT 39-86F rule.
>>>
>>> I could be wrong, but those parameters don't make sense. It's more
>>> likely the test temp is 39-86C, not F. Some cars have more detailed
>>> requirements, such as steady speed for X amount of time. This is a
>>> difficult code for do-it-yourselfers.
>>
>> Well, this link shows similar criteria:
>>
>> http://www.searchautoparts.com/sites...-docs/EVAP.pdf
>>
>> And, it's not just the ECT itself: both that link and Alldata say the
>> IAT and ECT need to be close to each other. That would be kind of
>> uncomfortable at 86C. I'll test the 'constant speed' idea - almost all
>> of our driving is in the city.
>>
>>> This is a difficult code for do-it-yourselfers.
>>
>> Yeah. I may end up punting it. But, $$$.
>
> Okay, I see that now, but those are the startup temps, not the
> conditions during which the test is run. In other words, if the temps
> are outside of the required range when you start the car, the test
> will not be run anytime during that drive cycle.
>

he's right about that, the PCM/ECM is looking for a long cold-soak.

Also, I think, the FF data showing the ECT out of range, is the problem
you need to solve first. Bad ECT, bad connector at ECT sensor, bad
pin-fit at ECM connector on ECT signal terminal, wire /almost/ broken in
harness (especially right-at the connector) are the usual culprits.

GW

On Sat, 24 May 2014 09:20:26 -1000, Geoff Welsh >
wrote:

>Bill Vanek wrote:
>> On Sat, 24 May 2014 09:49:18 -0400, George >
>> wrote:
>>
>>> On Fri, 23 May 2014 18:47:34 -0700, Bill Vanek >
>>> wrote:
>>>
>>>> On Fri, 23 May 2014 17:46:08 -0400, George >
>>>> wrote:
>>>>
>>>>> ('04 Cavalier) has been setting a p0455 code. All the components seem
>>>>> to be working, at least roughly:
>>>>> - purge valve operates, and blocks/passes when I blow on it.
>>>>> - vent valve, same.
>>>>> - canister blows through. (ie, doesn't seem plugged)
>>>>> - (I did change the gas cap.)
>>>>>
>>>>> Alldata (supposedly the same as the Helm book) says the EVAP test is run
>>>>> when ...
>>>>> - The engine is running.
>>>>> - ignition voltage is between 10-18 volts .
>>>>> - barometric pressure (BARO) is more than 75 kPa.
>>>>> - fuel level is between 15-85%.
>>>>> - engine coolant temp (ECT) is between 4-30C (39-86F).
>>>>> - intake air temp (IAT) is between 4-30C (39-86F).
>>>>> - start-up ECT and AT are within 9C (16F) of each other.
>>>>> - vehicle speed (VSS) is less than 121 km/h (75 mph) .
>>>>>
>>>>> We should meet that every time we run, this time of year. Instead, it
>>>>> usually takes multiple start/run cycles before the code sets ... AND,
>>>>> according to our scan tool, the EVAP test HAS NOT BEEN RUN before that.
>>>>> It's not that it sometimes passes: it says it hasn't been run. All the
>>>>> other diagnostics have, but not EVAP.
>>>>>
>>>>> Further confusing to me, when the test does run (and fails), the
>>>>> freeze-frame data shows an engine temp of ~175F, every time. This is
>>>>> consistent with where we are in the drive cycle - the engine is warm.
>>>>> This seems to directly violate the ECT 39-86F rule.
>>>>
>>>> I could be wrong, but those parameters don't make sense. It's more
>>>> likely the test temp is 39-86C, not F. Some cars have more detailed
>>>> requirements, such as steady speed for X amount of time. This is a
>>>> difficult code for do-it-yourselfers.
>>>
>>> Well, this link shows similar criteria:
>>>
>>> http://www.searchautoparts.com/sites...-docs/EVAP.pdf
>>>
>>> And, it's not just the ECT itself: both that link and Alldata say the
>>> IAT and ECT need to be close to each other. That would be kind of
>>> uncomfortable at 86C. I'll test the 'constant speed' idea - almost all
>>> of our driving is in the city.
>>>
>>>> This is a difficult code for do-it-yourselfers.
>>>
>>> Yeah. I may end up punting it. But, $$$.
>>
>> Okay, I see that now, but those are the startup temps, not the
>> conditions during which the test is run. In other words, if the temps
>> are outside of the required range when you start the car, the test
>> will not be run anytime during that drive cycle.
>>
>
>he's right about that, the PCM/ECM is looking for a long cold-soak.
>
>Also, I think, the FF data showing the ECT out of range, is the problem
>you need to solve first. Bad ECT, bad connector at ECT sensor, bad
>pin-fit at ECM connector on ECT signal terminal, wire /almost/ broken in
>harness (especially right-at the connector) are the usual culprits.
>
>GW

(OP) I agree, the ECT is odd. But, as noted, the ECT in the FF data is
consistent with the engine temp where the MIL comes on. And, when the
engine is cold, the ECT is nearly equal to the IAT. (Both are about 10F
higher than ambient right now ... maybe just retained heat?)

George

On Sat, 24 May 2014 22:53:40 -0400, George >
wrote:

>On Sat, 24 May 2014 09:20:26 -1000, Geoff Welsh >
>wrote:
>
>>Bill Vanek wrote:
>>> On Sat, 24 May 2014 09:49:18 -0400, George >
>>> wrote:
>>>
>>>> On Fri, 23 May 2014 18:47:34 -0700, Bill Vanek >
>>>> wrote:
>>>>
>>>>> On Fri, 23 May 2014 17:46:08 -0400, George >
>>>>> wrote:
>>>>>
>>>>>> ('04 Cavalier) has been setting a p0455 code. All the components seem
>>>>>> to be working, at least roughly:
>>>>>> - purge valve operates, and blocks/passes when I blow on it.
>>>>>> - vent valve, same.
>>>>>> - canister blows through. (ie, doesn't seem plugged)
>>>>>> - (I did change the gas cap.)
>>>>>>
>>>>>> Alldata (supposedly the same as the Helm book) says the EVAP test is run
>>>>>> when ...
>>>>>> - The engine is running.
>>>>>> - ignition voltage is between 10-18 volts .
>>>>>> - barometric pressure (BARO) is more than 75 kPa.
>>>>>> - fuel level is between 15-85%.
>>>>>> - engine coolant temp (ECT) is between 4-30C (39-86F).
>>>>>> - intake air temp (IAT) is between 4-30C (39-86F).
>>>>>> - start-up ECT and AT are within 9C (16F) of each other.
>>>>>> - vehicle speed (VSS) is less than 121 km/h (75 mph) .
>>>>>>
>>>>>> We should meet that every time we run, this time of year. Instead, it
>>>>>> usually takes multiple start/run cycles before the code sets ... AND,
>>>>>> according to our scan tool, the EVAP test HAS NOT BEEN RUN before that.
>>>>>> It's not that it sometimes passes: it says it hasn't been run. All the
>>>>>> other diagnostics have, but not EVAP.
>>>>>>
>>>>>> Further confusing to me, when the test does run (and fails), the
>>>>>> freeze-frame data shows an engine temp of ~175F, every time. This is
>>>>>> consistent with where we are in the drive cycle - the engine is warm.
>>>>>> This seems to directly violate the ECT 39-86F rule.
>>>>>
>>>>> I could be wrong, but those parameters don't make sense. It's more
>>>>> likely the test temp is 39-86C, not F. Some cars have more detailed
>>>>> requirements, such as steady speed for X amount of time. This is a
>>>>> difficult code for do-it-yourselfers.
>>>>
>>>> Well, this link shows similar criteria:
>>>>
>>>> http://www.searchautoparts.com/sites...-docs/EVAP.pdf
>>>>
>>>> And, it's not just the ECT itself: both that link and Alldata say the
>>>> IAT and ECT need to be close to each other. That would be kind of
>>>> uncomfortable at 86C. I'll test the 'constant speed' idea - almost all
>>>> of our driving is in the city.
>>>>
>>>>> This is a difficult code for do-it-yourselfers.
>>>>
>>>> Yeah. I may end up punting it. But, $$$.
>>>
>>> Okay, I see that now, but those are the startup temps, not the
>>> conditions during which the test is run. In other words, if the temps
>>> are outside of the required range when you start the car, the test
>>> will not be run anytime during that drive cycle.
>>>
>>
>>he's right about that, the PCM/ECM is looking for a long cold-soak.
>>
>>Also, I think, the FF data showing the ECT out of range, is the problem
>>you need to solve first. Bad ECT, bad connector at ECT sensor, bad
>>pin-fit at ECM connector on ECT signal terminal, wire /almost/ broken in
>>harness (especially right-at the connector) are the usual culprits.
>>
>>GW
>
>(OP) I agree, the ECT is odd. But, as noted, the ECT in the FF data is
>consistent with the engine temp where the MIL comes on. And, when the
>engine is cold, the ECT is nearly equal to the IAT. (Both are about 10F
>higher than ambient right now ... maybe just retained heat?)
>
>George

It still sounds like you're missing what the temp requirements are.
They need to be close to each other only at startup, and the temp
range is also only on startup. The test is not run at startup, and the
175 in the FF doesn't seem unusual for the test, although it does seem
a bit low if the engine is fully warmed up. Anyway, I don't think that
has anything to do with the code you're getting, but I'd still think
the thermostat might be bad. Have you watched live data as the car
warms up, or do you have a temp gauge? Does it take a very long time
to reach anything close to operating temperature?

But I could be misunderstanding what you're both saying.

On Fri, 23 May 2014 17:46:08 -0400, George > wrote:

>('04 Cavalier) has been setting a p0455 code. All the components seem
>to be working, at least roughly:
> - purge valve operates, and blocks/passes when I blow on it.
> - vent valve, same.
> - canister blows through. (ie, doesn't seem plugged)
> - (I did change the gas cap.)
>
>Alldata (supposedly the same as the Helm book) says the EVAP test is run
>when ...
> - The engine is running.
> - ignition voltage is between 10-18 volts .
> - barometric pressure (BARO) is more than 75 kPa.
> - fuel level is between 15-85%.
> - engine coolant temp (ECT) is between 4-30C (39-86F).
> - intake air temp (IAT) is between 4-30C (39-86F).
> - start-up ECT and AT are within 9C (16F) of each other.
> - vehicle speed (VSS) is less than 121 km/h (75 mph) .
>
>We should meet that every time we run, this time of year. Instead, it
>usually takes multiple start/run cycles before the code sets ... AND,
>according to our scan tool, the EVAP test HAS NOT BEEN RUN before that.
>It's not that it sometimes passes: it says it hasn't been run. All the
>other diagnostics have, but not EVAP.
>
>Further confusing to me, when the test does run (and fails), the
>freeze-frame data shows an engine temp of ~175F, every time. This is
>consistent with where we are in the drive cycle - the engine is warm.
>This seems to directly violate the ECT 39-86F rule.
>
>
>I would appreciate any thoughts on any of the above.
>
>Thank you.

Just FYI, this (GM?) link
https://service.gm.com/gmspo/mode6/p...4file2_L61.pdf

.... pretty explicitly shows the ECT/IAT conditions as being at
_startup_. I'm satisfied with that. However, it also says the test is
done "once per trip", which is pretty definitely not happening here.
Maybe the TP has to be 7-35% for the entire test interval (24 secs?)?
Even so, it still seems like we'd be hitting that.

.... And, what is "delta vacuum slosh"? Maybe just the variation in the
vacuum reading during the test?

G