Bogus codes from weak battery??

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#1
Make
Chevy
Model
Malibu
Year
1998
Miles
98852
Engine
3.1 V6
Car stored and not started for a month. But it started up seemingly fine. But CEL came on. Went 5 miles, stopped for 3 hours - restarted car- no problem. Had code checked on way home and it was P2000 a nox Adsorber Efficiency Below Threshold (Bank 1) Cyl 1 side.

Even though the car started and ran fine the 9 month old battery was very low. It took 5 hours of slow charge.

The following morning when the battery was fully charged I connected my ELM 327 and the P2000 was gone. But a P0341 Camshaft position sensor A bank 1 range/performance problem showed up.

I cleared all codes and drove for about 8 miles and there is no CEL.

So, do you think those two codes could have just been due to a very weak battery?
 

billr

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#2
No, I don't think that is likely; but I will sure hope I am wrong!
 

nickb2

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#4
Ok, I am confused, this car should NOT have given a p2000 code. That normally is reserved for diesel's. I checked my database, no mention of this for this engine/car.

Knowing this is a California car, I could be wrong. But somehow, I don't think so.

Are you sure it was not a U2000? Cuz that would make more sense for a dead battery condition and bogus codes.

It would be normal for this U codes to disappear and not comes back once vital B+ is regained. And it may also account for cam codes and other codes. I see this all the time.

SPI (serial peripheral interface data). When a battery goes down, or a loss of voltage occurs, this can cause MANY false flag codes and they will vanish after a time.

But as GRC said, that normally will not affect the cam sensor. SO be aware. The cam performance codes is not really represent a cam sensor malfunction. I have seen many swap sensors and code still comes back. So checking wiring and contact integrity is the first thing to do before throwing sensors at an engine.

Some times, bad engine grounds, bad PCM grounds etc are the essential cause of this.

This may not have been the answer you were looking for, but most assuredly I stand by what I wrote about the P2000 code being impossible for this car to have. Most likely a communication code (which are "U" prefixed).
 
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nickb2

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#5
You know you can catch freeze frames and data log with that elm 327, (happy you got one, they are fun to play with for the price they go for.).

You could have logged that and captured a screen shot of those codes and posted that here. That is if your so inclined to do so. But I do know your venerable age!! That is a joke and hope it will be taken in stride.

My grandmother and grandfather were still using VHS and tape cassettes when DVD had been out for eons.

The fact that you are using an elm 327 is impressive enough for me.

Happy new year BTW.
 

nickb2

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#6
Also, of note. With the elm 327, you can also check readiness monitors.

8 miles is not enough to know if the cam code will reset. You have to do a drive cycle which entails much more than 8 miles.

So drive it for a while, use the elm 327 to check if all mode 6 functions have passed. You will know this when all monitors show passed

Here is an article that may interest you. You will also note the presence of terms for NOX absorber. But this does not apply to you as you don't have a diesel engine.

If you don't have auto doctor, it is available on line. It is designed to work with the elm chipsets.

SO unless you really have an intermittent fault on the cam sensor ciruit, it will and should pass all monitors and the CEL will not light up after a proper drive cycle.

So just driving 8 miles is not enough. You have to do a proper cycle. Here is an example of what GM want for a drive cycle for cars of this era.

Link is here http://www.obdii.com/drivecycle.html

Article for auto doctor is here https://www.obdautodoctor.com/scantool-garage/using-obd2-mode-06-for-advanced-car-diagnostics


.
 

nickb2

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#7
Normally the included software included with the chip is basic and I usually throw the cd in the garbage bin.

But with the right software, you would be amazed at what a 15$ elm will do.

Since these came out, there is a wealth of info on the net. It is mind boggling.

How to sift through it all needs a lot of knowledge that you may not have the patience for. But, if your willing to ask me questions. I am more than willing to elaborate and help you layman term it. Forum rules prevent me from giving crack info. Which I try real hard not to do so. I think I have been a very good sport in this regards. Maybe santa claus forgot about me for being so nice. :D I only got a stainless steel thermos for christmas from my GF. That means shut up and go to work. :eek: Not what I wanted for the holidays.

Good thing she doesn't read this forum. I may get knocked out/abused in my sleep with said stainless thermos.

Here is a video on what auto doctor can do.
 
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billr

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#8
I could have been worse, she could have given you pruning shears...
 
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#9
Nickb2: I also discarded the Elm 327 CD and use Ian Hawkins Torque program.

Yes it was P2000 on a cheap scanner from a parts store that they let me use. I scanned and saw the code myself. When I looked it up at home and saw it pertained mostly to diesels I was thinking it was a false code or bad cheap reader. Especially when it did not show up the next day on my Elm 327 with Torque program.

I also knew that a complete cycle had not been done because there were 4 incomplete tests, Catalyst, Evap, O2 sensor and EGR.

I will let you all know in a few days what has happened. Thanks for taking time to help. At 85 years old, I like fixing cars here on my computer better than out in the cold garage. ;)

HAPPY NEW YEAR
 
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#12
Strong surge current when you hit the start button, okay switch the ignition switch to start. If the voltage drops to under 8.5 volts the PCM, ECU, or whatever you want to call it will not get a proper power on reset, to reset the program counter to zero. This has been a problem that really got strong around 1984.

And if you took your vehicle with a weak voltage start problem, will tell you, you need a new automatic transmission, radio, PCM, suspension computer, electronic dash, etc. Most common problem is the battery terminals themselves, has acid and corrodes. Can buy a battery terminal cleaner for a couple of bucks and coat with dielectric grease, helps prevent corrosion.

I just hook a digital scope across the battery terminals, hit the starter, it stores the voltage, if it drops below 8.5 volts, find the problems. Can also get weird codes. If the program counter is not reset to zero, starts reading code all over the place and gets screwed up, this problem first occurred in 1969 with the introduction of the microcomputer. About 14 years later, EPA got involved with automotive.
 

grcauto

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#13
I would be looking for at least 10V during crank. Most modules don't like much less.
 
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#14
NickD and all: It has now been 30 miles and several days and no codes. I have not had time to check with my Elm to determine if all systems checks have been made. 911 and ER visit with wife that was having trouble breathing has keep me busy.

But I think all is well. Unless I come back to this post I will call it fixed.
Or more appropriately say there never really was a problem at all except a weak battery causing bogus false codes.