battery memory saver

[PoorOwner]

When I use a ODB2 memory saver that supply from (another) battery to the ECU ,
does that mean the positive battery cable is going to be hot after removing the car battery? I wasn't going to find out the hard way but I would be careful not to sling it somewhere and hit other metal pieces.

 

[richfinn]

Yes, the trick is to put the now live positive battery terminal inside a nitrile glove, also be careful with alternator/Starter connections

 

[wafrederick]

Will not work on some.The newer VWs and Audis including BMW,trip to the dealer to have the PCM programmed.Wipes out the PCM out when the battery is replaced

 

[bonneyman]

I was thinking of trying a DIY memory saver I saw on-line as I can't stand re-programming the car radio after a repair. But I was told not to do it as any power applied could possibly cause a short and damage things.

 

[PoorOwner]

Technically shorts are when the positive touch the negative, that would be caused by the user not the device.

It could over load a circuit if it's running and you turn on something have a significant load.
I would like to see a small fuse on them.

 

[nadogail]

How about a 12 Volt Supply that can be plugged into your cigarette lighter socket to keep the system alive while your primary storage battery is disconnected.?

 

[toolmiser]

Not an expert here. I contacted The Car Doctor (Ron Ananian) about using a jump box thru the cigarette lighter (to hold the memory while changing a battery) and he said he had so/so luck doing that but to connect to the OBDII port instead.

 

[kbeefy]

How about a 12 Volt Supply that can be plugged into your cigarette lighter socket to keep the system alive while your primary storage battery is disconnected.?

I think thats what he is referring to.

Depending upon the vehicle, the key might need to be on to make that work.

I just hook jumper cables up to the battery terminals and another battery, a battery charger, or even another vehicle.

 

[AJHD]

Will not work on some.The newer VWs and Audis including BMW,trip to the dealer to have the PCM programmed.Wipes out the PCM out when the battery is replaced

Unfortunately this PCM non-sense is becoming more common and/or some vehicles need to have the battery monitor reset which requires a scan tool.

But anyway... I'm curious how this is going to effect stores like AutoZone or even Walmart that sell and replace batteries.

When I worked at AutoZone there were zero fucks given beyond the difficult and time consuming to remove batteries (which we declined to work on). We did nothing to reset battery monitors or use any form of memory saver.

I'm also not sure how many guys working in actual auto shops know about this stuff either... I'm sure overall and generally speaking this stuff will have a steep learning curve and I'd expect frequent problems to arise until it becomes "common knowledge".

 

[richfinn]

The OBD port on vehicles is permanently supplied with power with the ignition off and the key out. This is why this has become the preferred method over cigarette lighters where you may or may not need the ignition switched on to accessory position (where you may be powering up modules also)

The OBD memory saver devices are all fused, either with a an inline blade fuse or a glass fuse in the plug. Good ones have LED displays to tell you your connections are good, they supply power to T30 and a ground T31 with the ignition off so cannot "wipe" any modules.

It's 100% safe if you insulate the positive battery terminal after disconnection (I use a nitrile glove).

I use an OBD breakout box/jump pack to do the same thing to save carrying an extra tool, but Schumacher and EZ Red sell some nice quality memory savers.

The only issue is you need to confirm the OBD port is live before connecting the memory saver (hence the LEDs)

 

[2ndGearRubber]

Unfortunately this PCM non-sense is becoming more common and/or some vehicles need to have the battery monitor reset which requires a scan tool.

But anyway... I'm curious how this is going to effect stores like AutoZone or even Walmart that sell and replace batteries.

When I worked at AutoZone there were zero fucks given beyond the difficult and time consuming to remove batteries (which we declined to work on). We did nothing to reset battery monitors or use any form of memory saver.

I'm also not sure how many guys working in actual auto shops know about this stuff either... I'm sure overall and generally speaking this stuff will have a steep learning curve and I'd expect frequent problems to arise until it becomes "common knowledge".

They just don't reset it, and the battery just gets the wrong charging adaptations applied by the PCM. Same issue with lube techs. Shops don't have a scan tool, so unless a "real" tech does the battery swap they got out unprogrammed

They could get a basic scan tool designed for just resets, but they probably won't.

 

[signcrafter]

Will not work on some.The newer VWs and Audis including BMW,trip to the dealer to have the PCM programmed.Wipes out the PCM out when the battery is replaced

It wipes the PCM out, or just have to relearn the charging programming? I've done BMW batteries and only had to relearn the battery/charging on them. Basically like a throttle relearn after cleaning the throttle body. The PCM is used to a dirty throttle body and has adapted for it so when you clean it you need to relearn idle. Same with battery, it's adapted to charging the older battery and now that you have a new battery it needs to be reset to charge as the new battery calls for. Most decent scan tools can do this and no need to go to dealer. Unless something has changed and it does wipe out the PCM on newer vehicles. But I don't think that is the case, would mean every time a battery dies your car wouldn't run until towed to dealership to reprogram the PCM?

 

[richfinn]

It wipes the PCM out, or just have to relearn the charging programming? I've done BMW batteries and only had to relearn the battery/charging on them. Basically like a throttle relearn after cleaning the throttle body. The PCM is used to a dirty throttle body and has adapted for it so when you clean it you need to relearn idle. Same with battery, it's adapted to charging the older battery and now that you have a new battery it needs to be reset to charge as the new battery calls for. Most decent scan tools can do this and no need to go to dealer. Unless something has changed and it does wipe out the PCM on newer vehicles. But I don't think that is the case, would mean every time a battery dies your car wouldn't run until towed to dealership to reprogram the PCM?

It doesn't/can't wipe out a PCM, if you replace an AGM or EFB battery you may need to "match" (effectively erasing learned data values) the new battery to the Battery Monitoring System (BMS), nothing to do with the memory saver though, you might just be removing and refitting the same battery to access other components.

Programming modules is a different thing altogether, disconnection of a battery won't cause any harm if you follow manufacturers procedures.

 

[signcrafter]

It doesn't/can't wipe out a PCM, if you replace an AGM or EFB battery you may need to "match" (effectively erasing learned data values) of the new battery to the Battery Monitoring System (BMS), nothing to do with the memory saver though, you might just be removing and refitting the same battery to access other components.

Programming modules is a different thing altogether, disconnection of a battery won't cause any harm if you follow manufacturers procedures.

That was my understanding also and have done a few with my autel, but wafrederick said anytime you replace a battery in bmw it wipes the PCM and have to take to dealer to program. Was hoping to clear that up so there isn't bad info being passed on. Thanks

 

[richfinn]

That was my understanding also and have done a few with my autel, but wafrederick said anytime you replace a battery in bmw it wipes the PCM and have to take to dealer to program. Was hoping to clear that up so there isn't bad info being passed on. Thanks

I work on quite a few modern BMWs and have never experienced such a thing, occasionally I have come across failed battery monitor sensors (which can prevent cranking) either from water ingress or poorly performed jump starts. They will usually start if you unplug the sensor.