1996 NISSAN MAXIMA , LOST GAS CAP, CHECK ENGINE LIGHT CAME ON

Hi, I lost my gas cap, and the check engine light came on, I assumed because of the gas cap. I replaced the gas cap, and the light hasn't gone away. I also unplugged the battery for 5 minutes thinking that would do it. It still comes on. Any suggestions? Car runs fine.

Reply to
Da 4 Horsemen.
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Unplugging the battery for five minutes will not do it. There is a screw on the ECM that will cause it to blink out the codes and then reset them.

Alternatively, many of the major auto parts stores, like AutoZone, will connect a reader to it, get the trouble codes out and reset it for you, usually for free. Make sure you write down the code numbers before you reset it in case its not the gas cap.

If it is just the gas cap and you replaced it with the correct cap, it will reset itself and turn off the light after several driving sequences if it detects the problem that lit the light is no longer present. Give it a week or so and if the light doesn't go off by itself, try AutoZone.

Reply to
E. Meyer

It will take a few drive cycles to clear itself if the cap was the problem. Just drive it a week and it should go out.

Reply to
Steve W.

No you NEED to have the code reset.. Driving a million drive cycles won't remove the code even if the light goes out.

Just have the code reset and you should be good to go. You can also purchase your own code reader for cheap.

Reply to
m6onz5a

Not true. Take a glance through the FSM for this car. IF its the gas cap code, it will go away when the light goes out. But, you are right in that the only way to really know for sure if its the gas cap code is to read the codes.

Reply to
E. Meyer

m6onz5a wrote in news:0484e9ea-fae4-4a3e-8908- snipped-for-privacy@fx12g2000vbb.googlegroups.com:

The light will go out the next time the engine's computer runs the readiness tests and the system passes the tests. That's how OBD-II works.

If the light never does go off, then there is still a problem of some kind, and the system is failing to pass its tests.

My understanding is that at least some EVAP tests will run even when the engine is not operated, but fuel tank level must be between a certain maximum and minimum.

Reply to
Tegger

just because the light goes out doesn't mean you don't have any codes.

So, you're saying if it's a gas cap code it resets itself, but all other codes don't reset???????

Reply to
m6onz5a

m6onz5a wrote in news: snipped-for-privacy@d7g2000vbv.googlegroups.com:

No, I just said the light will go off, which is all the owner needs to have happen. Even emissions testers are only concerned with readiness-monitor status, and an illuminated MIL.

Reply to
Tegger

snipped-for-privacy@d7g2000vbv.googlegroups.com:

I believe if emmisions test stations find a code stored they won't pass the vehicle.

Reply to
m6onz5a

Most of the EVAP stuff uses engine vacuum to test. Basically it applies vacuum to the system. It times how long it takes to reach a set point and then times how long it takes to leak down. As long as both times are withing the normal range it says it's OK. On some engines there is a separate pump that also works with the EVAP system.

EVAP codes usually require fuel levels between 25% and 75-80%. Plus operating temps and exterior temps in a certain range. The the test will run. They won't run outside of this envelope and some codes require the test to be passed more than once to reset the code. Most are about 5 drive cycles with no failure.

Reply to
Steve W.

innews: snipped-for-privacy@d7g2000vbv.googlegroups.com:

Depends on the code. Plus it also depends on when the code was set.

If you pull in, the MIL is off and the scanner says that the monitors are OK (you're allowed two non-complete monitors in NY). The scanner then checks for certain pending codes. If they are clean then you're all set. Then you just need to pass the mechanical/safety part.

If you're in the city then you also get the tailpipe sniffer and all the related crap. So far that hasn't been pushed up-state. Mainly because it hasn't worked in the city due to the exemptions in the law.

Reply to
Steve W.

On this particular car ('96 Maxima), if it was the gas cap code (nissan code

0705 when you blink it out on the light, P0440 if you use a scan tool) the light will go off after three consecutive driving sequences when the error is no longer detected.

The code will remain in the ECU memory for 40 driving cycles then disappear unless it is reset (disconnect battery for 24 hours, reset with screw on ECU, or reset with scan tool).

There is a catch for emissions tests - if the light goes out by itself because the condition has gone away, the ECU will report ready. If the ECU & codes are explicitly reset, then the ECU will report some parameters as not ready (and it will not pass the emissions test in many states) until a number of specific driving cycles are successfully completed, which can take a week or more of driving. So, if an emissions test is coming up, you are better off with this car to let the light go off by itself rather than reset the codes.

Reply to
E. Meyer

"Steve W." wrote in news:igicqu$id9$ snipped-for-privacy@speranza.aioe.org:

What I read (forget where, maybe Click and Clack)...

Cars can sit unused for extensive lengths of time with gas in the tank. It is possible for fuel vapors to escape into the atmosphere even in the absence of engine operation. Therefore, the EVAP will run on its own regularly in order to test for vapor leakage even if the car is not used. This means that the EVAP imposes a parastic draw on the storage battery which can cause it to drain more quickly than batteries did before the advent of ODB-II EVAP systems.

How would the driver would be notified that leakage has occurred when the car is sitting unused? I have no idea. But people who work for governments don't usually seem to be well-acquainted with logic.

Reply to
Tegger

"E. Meyer" wrote in news:C9522910.268B8% snipped-for-privacy@msn.com:

The ECM will only report "ready" on those monitors which have passed their tests.

Certain models have small defects that will cause their OBD-II monitors to report "not ready" even if nothing is wrong. Many jurisdictions accommodate such inherent problems by permitting two or more "not ready" monitors.

Clearing codes resets ALL readiness monitors, and that's a bitch. Why do they do that?

At least some automakers have produced documents that detail the drive- cycles necessary to force all the readiness tests to complete. It's often possible to make them all run in one day.

Reply to
Tegger

None of the ones I know of will run the EVAP cycle unless the engine is actually running. They cannot because the source of the vacuum for the tests is the engine. They run the tests almost immediately on start up if the conditions are correct. Most of the parasitic draw is from the ECM and the clock. Then if you have things like keyless entry or remote start you can add more drain.

Reply to
Steve W.

"Steve W." wrote in news:igj2h5$6jq$ snipped-for-privacy@speranza.aioe.org:

I wish I could remember where I read about the EVAP running even when the engine is off. Maybe it wasn't Click and Clack, but just Usenet.

I just studied some late-model EVAP diagrams I have access to, and there is indeed no separate pump, so engine vacuum can only be the source of testing vacuum, as you say.

Reply to
Tegger

A lot of the late model stuff is natural vacuum leak detection. Done with engine off.

Reply to
Steve Austin

Steve Austin wrote in news:4d2da00c$0$17820$ snipped-for-privacy@news.westelcom.com:

How do they do it?

Reply to
Tegger

Vent is closed. As gas fumes contract and fuel cools a slight vacuum is pulled in the tank. This closes a switch.

Reply to
Steve Austin

Steve Austin wrote in news:4d2f907c$0$17966$38cefb40 @news.westelcom.com:

Considering the current system can detect the very tiniest of pinholes, what's the tolerance? How long does it allow for vacuum to leak-off before it decides there's a problem?

Reply to
Tegger

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