ECU EXPERTS: Keeping memory in the ECU when using a master switch?
Thread Starter
Melting Slicks
Joined: Mar 1999
Posts: 2,830
Likes: 20
From: Las Vegas Nevada
ECU EXPERTS: Keeping memory in the ECU when using a master switch?
I have a master switch in my car which I will be using fairly frequently. It is connected to the negative side of the battery circuit. I was thinking - every time I use the master switch to disconnect the battery for any length of time isn't the ECU going to lose it's memory and have to re-learn again?
In order to avoid the situation above I would need to keep a constant ground to the circuit in the ECU that retains memory. IIRC there are four or five grounds to the ECU. Does anyone know exactly which ground I should ground direct to avoid loosing the ECU memory?
thanks,
In order to avoid the situation above I would need to keep a constant ground to the circuit in the ECU that retains memory. IIRC there are four or five grounds to the ECU. Does anyone know exactly which ground I should ground direct to avoid loosing the ECU memory?
thanks,
Le Mans Master
Joined: Jan 2002
Posts: 9,036
Likes: 13
From: Edmonton AB
These versions of what you have claim to retain ECU memory.
If that is not satisfactory, wouldn't one of those devices that plugs
a 9VDC battery into the cigarette lighter hold the ECU memory while
the primary battery is disconnected? You could make your own with
a DC adapter from Radio Shack modified to be hooked up to a gel cell.
.
If that is not satisfactory, wouldn't one of those devices that plugs
a 9VDC battery into the cigarette lighter hold the ECU memory while
the primary battery is disconnected? You could make your own with
a DC adapter from Radio Shack modified to be hooked up to a gel cell.
.
Thread Starter
Melting Slicks
Joined: Mar 1999
Posts: 2,830
Likes: 20
From: Las Vegas Nevada
Originally Posted by Slalom4me
If that is not satisfactory, wouldn't one of those devices that plugs a 9VDC battery into the cigarette lighter hold the ECU memory while the primary battery is disconnected? You could make your own with a DC adapter from Radio Shack modified to be hooked up to a gel cell.
The kill switch I have is a key type. No provision to retain battery memory.
Le Mans Master
Joined: Jan 2002
Posts: 9,036
Likes: 13
From: Edmonton AB
Why change it (the gell cell, right?) out each spring?
If the car will be anywhere there is some source of light, then use
a small solar panel to keep it charged. This kind of approach is
used to maintain batteries in roadside devices. Those gell cells
are in the emergency hallway lighting units and they last for quite
awhile there.
.
If the car will be anywhere there is some source of light, then use
a small solar panel to keep it charged. This kind of approach is
used to maintain batteries in roadside devices. Those gell cells
are in the emergency hallway lighting units and they last for quite
awhile there.
.
Le Mans Master
Joined: Jan 2002
Posts: 9,036
Likes: 13
From: Edmonton AB
You are innovative and like to try stuff. What about using a small
gauge fusible link across the terminals of the key switch.
You'll need to puzzle out the details but basically, the circuit
would still be hot with the key off. However, the current would
be routed through the fusible link. This would be sized to have
sufficient capacity for the demands of the ECU and courtesy
lights - if someone tried to start the car, the fusible link would
go phhhtttt.
Or do the same thing with a MiniFuse.
** --- DISCLAIMER ------------------------- **
Folks, the information above is provided with the aim of
suggesting a very general overview for consideration, it is
not intended as a detailed or complete solution. If you follow
this approach, overlook some important consideration and
experience an electrical malfunction, then all responsibility
rests with you.
** ------------------------------------------ **
.
gauge fusible link across the terminals of the key switch.
You'll need to puzzle out the details but basically, the circuit
would still be hot with the key off. However, the current would
be routed through the fusible link. This would be sized to have
sufficient capacity for the demands of the ECU and courtesy
lights - if someone tried to start the car, the fusible link would
go phhhtttt.
Or do the same thing with a MiniFuse.
** --- DISCLAIMER ------------------------- **
Folks, the information above is provided with the aim of
suggesting a very general overview for consideration, it is
not intended as a detailed or complete solution. If you follow
this approach, overlook some important consideration and
experience an electrical malfunction, then all responsibility
rests with you.
** ------------------------------------------ **
.
Last edited by Slalom4me; May 28, 2006 at 01:47 AM.
Thread Starter
Melting Slicks
Joined: Mar 1999
Posts: 2,830
Likes: 20
From: Las Vegas Nevada
Originally Posted by Slalom4me
You could make your own with
a DC adapter from Radio Shack modified to be hooked up to a gel cell.
.
a DC adapter from Radio Shack modified to be hooked up to a gel cell.
.
thanks for the help,
Le Mans Master
Joined: Jan 2002
Posts: 9,036
Likes: 13
From: Edmonton AB
I just saw that as I came back to post this, I'll reply on RS in
a moment. The answer may be redundant after you take a look
below.
I have a rigid panel made by ICP Global that I've used for a number of
years. Didn't see it in a quick search but did come across one of their
flexible designs, along with some accessories that may be of interest.
A sampler of something that might be of interest (I've no experience
with this particular vendor.)
The newer units have regulators these days, built-in or as an optional
module. These things don't require strictly sun light, mine generates
juice in the presence of incandescent & other sources.
Also, the subject has come up before. Here is a thread from the
past with some ideas for you - Lighter Socket - Battery Tender???
.
a moment. The answer may be redundant after you take a look
below.
I have a rigid panel made by ICP Global that I've used for a number of
years. Didn't see it in a quick search but did come across one of their
flexible designs, along with some accessories that may be of interest.
A sampler of something that might be of interest (I've no experience
with this particular vendor.)
The newer units have regulators these days, built-in or as an optional
module. These things don't require strictly sun light, mine generates
juice in the presence of incandescent & other sources.
Also, the subject has come up before. Here is a thread from the
past with some ideas for you - Lighter Socket - Battery Tender???
.
Thread Starter
Melting Slicks
Joined: Mar 1999
Posts: 2,830
Likes: 20
From: Las Vegas Nevada
So I use a solar panel to keep the gel cell battery charged? How will I know the size I need?
Didn't know Radio Shack carried these. Than again I've never gone looking. Would they have the small solar panels as well? I suppose I would want to put this on the dash?
Thanks for the link as well. I'm not worried about the battery going dead, I just don't want to lose the ECU memory.
thanks again,
Didn't know Radio Shack carried these. Than again I've never gone looking. Would they have the small solar panels as well? I suppose I would want to put this on the dash?
Thanks for the link as well. I'm not worried about the battery going dead, I just don't want to lose the ECU memory.
thanks again,
Last edited by VtVette; May 28, 2006 at 01:45 AM.
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Le Mans Master
Joined: Jan 2002
Posts: 9,036
Likes: 13
From: Edmonton AB
I searched RadioShack.com (and www.thesourcecc.com, the outfit
the CDN RS stores morphed into when someone had a snit and decided
to split.) Can't find what I've walked in and bought before - a fused
cigarette adapter with a length of cord attached. But here are a
couple of close proximates
270-1509 12VDC 7.5A Power Plug
270-1521 Vehicle Power Adapter Plug with Banana Jack
I'm suggesting a gel cell because I don't think a conventional 9 VDC
radio battery is going to last very long. You could pull fuses, but
this is a hit on the convenience factor.
My vote is to get a sense of how much current draw you anticipate,
select a battery with sufficient Ah capacity and then maintain the
battery with a suitably sized solar panel. A 5A battery theoretically
provides you 5 hours of current when connected to 1A draw.
Here's a link with some sample gel cells, scroll down to the 12 VDC
units.
This link has some useful information about battery charge and
discharge considerations. You'll need to scroll for it.
.
the CDN RS stores morphed into when someone had a snit and decided
to split.) Can't find what I've walked in and bought before - a fused
cigarette adapter with a length of cord attached. But here are a
couple of close proximates
270-1509 12VDC 7.5A Power Plug
270-1521 Vehicle Power Adapter Plug with Banana Jack
I'm suggesting a gel cell because I don't think a conventional 9 VDC
radio battery is going to last very long. You could pull fuses, but
this is a hit on the convenience factor.
My vote is to get a sense of how much current draw you anticipate,
select a battery with sufficient Ah capacity and then maintain the
battery with a suitably sized solar panel. A 5A battery theoretically
provides you 5 hours of current when connected to 1A draw.
Here's a link with some sample gel cells, scroll down to the 12 VDC
units.
This link has some useful information about battery charge and
discharge considerations. You'll need to scroll for it.
.
Le Mans Master
Joined: Jan 2003
Posts: 8,596
Likes: 19
From: Portland Oregon
Why bother? The reason I ask is, for the most part earlier cars don't really "learn" anything. Once they go into closed loop the o2 sensor is the last control element in the the process. With saying that the o2 sensor is the king, the ECM process his signals and changes the fuel trims to control proper fueling for your engine. This all takes a few seconds once it is in closed loop. Even the newer PCMs don't take long to relearn fuel trim numbers. During dyno tuning sessions on my chassis dyno, and after a reflash or a change in programming. I always initiate a fuel trim reset, once done the PCM or ECM takes less than 5 seconds for its fuel trims to settle down. The only thing you may want to do this for is to save any stored codes that may set in case of a sensor failure. In all the old chipped ECMs, you loose battery power means you loose any stored codes. This is true for OBD1 stuff up to 1995. Anything OBD2, the codes are stored in non-volatile memory and disconnecting the battery will not result in lost DTC memory.
Last edited by tjwong; May 28, 2006 at 01:57 PM.
Thread Starter
Melting Slicks
Joined: Mar 1999
Posts: 2,830
Likes: 20
From: Las Vegas Nevada
Thanks for all the advice. My main concern was the computer having to "relearn" every time I kill the battery. From what tjwong says this is not really an issue. I guess I will leave my setup the way it is unless anyone else chimes in with any other opinions or advice.
Le Mans Master
Joined: Feb 2006
Posts: 8,753
Likes: 9
From: Louisiana
Originally Posted by tjwong
Why bother? The reason I ask is, for the most part earlier cars don't really "learn" anything. Once they go into closed loop the o2 sensor is the last control element in the the process. With saying that the o2 sensor is the king, the ECM process his signals and changes the fuel trims to control proper fueling for your engine. This all takes a few seconds once it is in closed loop. Even the newer PCMs don't take long to relearn fuel trim numbers. During dyno tuning sessions on my chassis dyno, and after a reflash or a change in programming. I always initiate a fuel trim reset, once done the PCM or ECM takes less than 5 seconds for its fuel trims to settle down. The only thing you may want to do this for is to save any stored codes that may set in case of a sensor failure. In all the old chipped ECMs, you loose battery power means you loose any stored codes. This is true for OBD1 stuff up to 1995. Anything OBD2, the codes are stored in non-volatile memory and disconnecting the battery will not result in lost DTC memory.
