Is it bad to keep deleting OBD codes?

Thread Starter

strantor

Joined Oct 3, 2010
5,159
I have a problem with my EVAP system that keeps generating P0442/P0455. I plan to fix this when I can afford to, but in the mean time I've been connecting my scanner and deleting the code every time the check engine light comes on. Is that bad practice? Obviously best practice is to fix the problem, and I am, but is there a finite number of times you can delete these codes before you cause more problems? What kind of storage technology is the ECU using for this? ROM? RAM?
 
Last edited:

MaxHeadRoom

Joined Jul 18, 2013
19,165
I don't think you will have any problem by repeated deletion, I have done this several times, It seems the most prevalent causes of check engine is the pollution control components.
On my vehicle the code comes up on the one line digital display.
Max..
 

narkeleptk

Joined Mar 11, 2019
375
pcms usually store the DTCs in eeproms like 95080 or in emulated eeprom sections of mcu's like mpc5xxx. I dont think you will have any issues clearing them over and over. It would probably even clear itself after a short drive if the code is not active.
 

Audioguru

Joined Dec 20, 2007
11,251
Your EVAP system leaks. It cost you wasted fuel and it is polluting our air. It might even be a fire hazard.
Since you cannot afford to fix it then you should sell the car and ride a bus or a bicycle.
 

joeyd999

Joined Jun 6, 2011
4,268
Your EVAP system leaks. It cost you wasted fuel and it is polluting our air. It might even be a fire hazard.
Since you cannot afford to fix it then you should sell the car and ride a bus or a bicycle.
I make sure to spill a few drops at the pump after every fill-up.

Just because I know it's annoying to some.
 

shortbus

Joined Sep 30, 2009
7,078
Your EVAP system leaks. It cost you wasted fuel and it is polluting our air. It might even be a fire hazard.
You need to do more research on this, EVAP has nothing to do with mileage or wasted fuel. The chances of fire form a failed EVAP are so minuscule there is probably no way to measure it.
 

Thread Starter

strantor

Joined Oct 3, 2010
5,159
Your EVAP system leaks. It cost you wasted fuel and it is polluting our air. It might even be a fire hazard.
Since you cannot afford to fix it then you should sell the car and ride a bus or a bicycle.
I'm glad to see you're back AG. The forum is incomplete without your unabashed codgery :p.
 
Remember that codes can be erased by disconnecting the battery. History codes I'm not sure.

The speedometer probably has a wear mechanism built in. e.g. x number of writes, change the pointers to different memory locations.
 

narkeleptk

Joined Mar 11, 2019
375
@KeepItSimpleStupid
I'm not to sure about unhooking the battery to clear any codes, If that works its going to be pretty rare cases.
I do spend a lot of time in the hex data of automotive modules tho, can't say I have ever seen the write locations for dtc's or other constantly changing data (like mileage) ever switch around. More likely that if it was not able to write then your going to start getting control module failure codes instead. Also, the speedometer has nothing to do with the dtc's in other modules only its own codes. EVAP will be in the engine control module.
 

bwilliams60

Joined Nov 18, 2012
1,199
There is no harm in erasing codes in a car numerous times. EEPROMS shohld be able to be written to a million times or more without damage, similar to a USB stick only better. The only thing you will do is reset the system monitors over and over again which means everything will not be working properly until you have driven it several miles. Just in time to reset it again. As for disconnecting a battery, it does nothing unless you short the cables together which is considered a hard reboot. Even at that, codes including historical codes are not always reset.
As for your EVAP issue, I havent looked up the code but gas caps leaking, filler necks leaking are most common. Get a smoke tester and find the leak. Google it, you will see leaks are easy to find. Good luck.
 

Thread Starter

strantor

Joined Oct 3, 2010
5,159
Remember that codes can be erased by disconnecting the battery. History codes I'm not sure.

The speedometer probably has a wear mechanism built in. e.g. x number of writes, change the pointers to different memory locations.
I remember resetting codes on my early '90s truck by disconnecting the battery. But that was OBD1 and I have a scanner for this OBD2. I'm not sure if disconnecting the battery works on this but even if it did, I would keep using the scanner. The main reason I don't just ignore the light is because if any REAL problems come up I won't know about it. And just resetting the codes without confirming they're the same evap codes would be the same thing.
 

shortbus

Joined Sep 30, 2009
7,078
I'm not to sure about unhooking the battery to clear any codes, If that works its going to be pretty rare cases.
I do know it works on a 2009 Chevy Colorado. But it won't work by just unhooking the cables for a short time. I just got done doing a timing chain/sprocket change on my Colorado. Due to health problems and weather(I have to work in the driveway) it took about a month to do. When I started the truck up all of the many timing codes had been erased and they were there when I started the job.
 
But it won't work by just unhooking the cables for a short time. I just got done doing a timing chain/sprocket change on my Colorado.
I have to believe that. Think airbag battery cable disconnect time before you can safely disconnect an airbag. That tie seems to be about 15 minutes. I'll be removing my first airbag in the near future toreplace a multi-function switch.

Some of the new processors (e.g. Renasys) have a wear mechanism built in.

Resets mess up the "tuned parameters" where driving cycles set those values.

While we are on car troubles, I have one: 2000 Impala; no codes set.

What I know:

Engine must be warm.
On a warm start. idle MAY be eratic for a minute or so.

On one particular long hill, most of the time, about midway engine RPM will studder. Otherwise, it may happen when cruising.

What I've done.
1) Disconnect MAF sensor (problem exaborates)

2) Cleaned sensor and reset codes
problem still seems to exist.
 

Thread Starter

strantor

Joined Oct 3, 2010
5,159
I have to believe that. Think airbag battery cable disconnect time before you can safely disconnect an airbag. That tie seems to be about 15 minutes. I'll be removing my first airbag in the near future toreplace a multi-function switch.

Some of the new processors (e.g. Renasys) have a wear mechanism built in.

Resets mess up the "tuned parameters" where driving cycles set those values.

While we are on car troubles, I have one: 2000 Impala; no codes set.

What I know:

Engine must be warm.
On a warm start. idle MAY be eratic for a minute or so.

On one particular long hill, most of the time, about midway engine RPM will studder. Otherwise, it may happen when cruising.

What I've done.
1) Disconnect MAF sensor (problem exaborates)

2) Cleaned sensor and reset codes
problem still seems to exist.
Read up on throttle position sensor (TPS). When it fails it can manifest in a wide array of strange symptoms which don't trigger any lights, most commonly including what you describe.
 

narkeleptk

Joined Mar 11, 2019
375
I have to believe that. Think airbag battery cable disconnect time before you can safely disconnect an airbag. That tie seems to be about 15 minutes. I'll be removing my first airbag in the near future toreplace a multi-function switch.
Airbag modules have very large capacitors I assume the recommended wait is pretty much just waiting for the caps to discharge. The same with the PCM doing its self check ups after disconnecting KAM for too long (and it may or may not reset the previously stored code depending on its tests).
I reset a lot of crashed srs modules for body shops (some use those renesas mcu's you mentioned, tho I have never seen them change write locations) 80% of the time they do not even bother unhooking the battery when changing the bags or removing the modules surprisingly. As long as the ignition is in OFF the srs module should not have any power to it. Still since its so easy to do and be safe I generally will unhook the batteries myself just for liability reasons if I am removing/installing the modules. I have known a few guys to explode the new bags they just put in because they had the switch on when plugging the modules in. It lays them out for a day or two. They all say it felt like a bomb went off beside them.
 
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