My PCM has a short term memory
My PCM has a short term memory After the car sits for a few hours and I start it up, all the gauges on the dash flash to there max reading, then back to a 0 rating, then go to the correct setting. For example. Tach with go to 7K, then down to 0, then up to 900 rpm. The trip meter also resets to 0. Also seems the car has to relearn how to idle. If I go on a trip and shut the car off for a short period, say to get gas or run into the store it will retain it's memory... any idea what would cause this?
Dan
99 T/A MTI programming.
Dan
99 T/A MTI programming.
It sounds like a short or improper contact. I know for a fact that when my car would do that, it was due to the battery being low. I have noticed some vehicles had either a bad contact behind the dash for the gauge cluster or the battery terminals were loose.
You either have a battery or alternator on it's way out, or a bad connection.
And since you have a 99 you will get the trip reset ...... Mine does the same when my lightweight battery gets low.
And since you have a 99 you will get the trip reset ...... Mine does the same when my lightweight battery gets low.
Hmmm funny I have the same problem. I thought it was because I moved the battery to the back but I checked all my connections 100 times and used 0 gauge wire to try to fix it and it still did it. It didn't seem to have any other effect on my car other than it reseting the OD so I just ignored it. This is saying it's the gauge cluster itself? So I will have to replace the gauge cluster to correct this problem?
UltraZ,
As far as function I don't see the gauge replacement being a must. It will just reset the trip.....
It might not like the battery relocation but as long as it starts fine and you can live with the trip reset....I wouldn't bother. Mine works fine with a regular battery but it resets sometimes with the lightweight one. I've gotten used to it during "race season". After that the stocker goes back in.
As far as function I don't see the gauge replacement being a must. It will just reset the trip.....
It might not like the battery relocation but as long as it starts fine and you can live with the trip reset....I wouldn't bother. Mine works fine with a regular battery but it resets sometimes with the lightweight one. I've gotten used to it during "race season". After that the stocker goes back in.
I'm running a lightweight battery in the stock battery location as well. Maybe this is the source. The alternator did just go out, but I replaced it and I have the same problem. The car doesn't have any problems starting and it has been doing this for about a year.
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Originally Posted by jay_99z
UltraZ,
As far as function I don't see the gauge replacement being a must. It will just reset the trip.....
It might not like the battery relocation but as long as it starts fine and you can live with the trip reset....I wouldn't bother. Mine works fine with a regular battery but it resets sometimes with the lightweight one. I've gotten used to it during "race season". After that the stocker goes back in.
As far as function I don't see the gauge replacement being a must. It will just reset the trip.....
It might not like the battery relocation but as long as it starts fine and you can live with the trip reset....I wouldn't bother. Mine works fine with a regular battery but it resets sometimes with the lightweight one. I've gotten used to it during "race season". After that the stocker goes back in.
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I have a '99 Z28 as well.
If I'm showing good voltage when the car is running could it still be my alternator or battery? There is no hesitation on startups at all and even when it resets there is no issue with idling(although its a little low at 500rpm)
If I'm showing good voltage when the car is running could it still be my alternator or battery? There is no hesitation on startups at all and even when it resets there is no issue with idling(although its a little low at 500rpm)
TECH Enthusiast
Joined: Sep 2003
Posts: 503
Likes: 1
From: Texas
Originally Posted by TAGOES11S
After the car sits for a few hours and I start it up, all the gauges on the dash flash to there max reading, then back to a 0 rating, then go to the correct setting. For example. Tach with go to 7K, then down to 0, then up to 900 rpm. The trip meter also resets to 0. Also seems the car has to relearn how to idle. If I go on a trip and shut the car off for a short period, say to get gas or run into the store it will retain it's memory... any idea what would cause this?
Dan
99 T/A MTI programming.
Dan
99 T/A MTI programming.
Hope this helps,
Maggie
TECH Senior Member
Joined: Nov 2001
Posts: 7,036
Likes: 1
From: Lake Zurich, IL
Originally Posted by MAXIMO
Question on this, Would this mess up a tune????
Once a car is tuned, it's stored in the PCMs flash memory, so simply losing power won't cause it to be lost (the tune) ... even losing power momentarily isn't enough to clear the learned info in the PCM (such as fuel trims)
Low voltage will cause this... but the early 99 pcm software had a fault that caused it to reset some of the memory values and act exactly as you describe. You can have the software updated at a dealer or find someone that can reflash the computer with a newer version.
Hope this helps,
Maggie
Hope this helps,
Maggie
TECH Enthusiast
Joined: Sep 2003
Posts: 503
Likes: 1
From: Texas
