ive recently replaced the stock ecm in my car with an after market standalone.
But for inspection i need to make sure that the check engine light come son and then goes off like it normally would with the stock ecm when u first start the car. anyone know of anything of the shelf that can do this or know how to build something to do this?

 

where do you live where they take the time to plug something in and turn your check engine light on? That's a little **** for OBD1

If you knew what they connect to your obd1 system, you can easily rig up a relay to turn the light on when they plug their thing in. But that wont fly if they do anything else like tell it to stop blinking

 

You could do what you want (i.e. turn the SES light on when the ignition is turned on and back off when started) by using two double pole double throw (or single throw) relays. The first will energize when the ignition is turned on, then the second will latch (turning off the light) when turned to crank, then unlatch when the ignition is turned back off. The only problem here is if the car doesn’t start when turned to crank as the light will turn of and remain off even if it doesn’t start. This could also be done with logic circuits but the former would be easier for the DIYer.

I have to leave shortly so I don’t have time to draw it up now. Let me know if interested and I’ll draw it up when I return.

 

If the new ECM has an output for a SES light, why not connect that to the dash light?

Lou

 

Its part of the visual inspection for an emissions test. The SES light must come on and blink once when you turn the key on, and the light must go out when you start the car. The old Accel DFI version 6 did not have a provision for this, but I dont know if the newer versions do or not.

 

yeah that would be great whenever u have the time
my ecm does not have this provision im running a megasquirt not an acell dfi but i just thought about seeing if i could program some sort of rpm based output to trigger the light i.e on @ 0 rpm and off at 400 rpm

 

Since it needs to flash once, a timer or two would need to be added to the relays. If electronics are to be used, it would be easier to use a microcontroller than digital logic. Do you have chip burning capability or know anyone who can burn a micro such as a PIC for you? Is there any output on your unit that is only active when the engine is actually running? I guess a tach signal from your dizzy would work.

 

That's what I was thinking of, just a simple frequency switch. They're easy to make (if you know how) but expensive to buy (cuz they realize that not many people know how ). If you have any electronic skills, you can build one out of scrap parts like a capacitor, transistor and a few resistors.

Lou

 

yeah i do have a few outputs available to trigger the light on and off unfortunatly none of them would be able to flash the light once and then shut it off

my electronics go as far as being able to solder,if i have a parts list and a simple diagram i can build watever, i just cant design stuff i dont know enough

if i use an rpm based output i quess on @ 0 rpms with a 2 sec delay on a timer to flash then when the motor is started and rpms are above 400 the output will kill all power to the circut killing the light.

what would i need to buy or build to get a timer on the circut to flash the light one time

basically the output circut would supply 12 volts to a relay when the motor is below 400 rpms and kill the circut once the motor is started,so just need something to flash the light one time. im assuming this would be the easiest way

 

Actually, I just thought of an even simpler way.
Our cars do not have a charging indicator. But our alternators have a wire for that.
Normally, the charging indicator is on when the engine is stopped and the alternator is not producing electricity (instead, it is consuming it which lights up the indicator light - but I don't want to get into crazy details here discussing field excitation coils etc). Once the engine starts up and the alternator produces enough electricity, the light turns off.

You can use the CEL for the same purpose.

The alternator has a brown wire in the top connector. This wire goes to the firewall to the fan relay. Snip it off (before it reaches the relay wiring) and run it through the firewall.
Find the brown/white wire behind your instrument cluster. That's the wire for your SES (CEL) light. Snip it. Tie the brown wire to the end that's coming out of the instrument cluster.
Now the CEL is powering the alternator excitation coil. Turn the key on, the light should come on. Start the car and the light should turn off and you should be charging.

I have no idea if this has been tried before. But if it fails, don't blame me! Ok, blame me.

Hope this helps.
Lou

 

not a bad idea, but the light needs to come on when u turn the key on, and then flash one time before the car starts and the light shuts off

 

A 556 dual timer IC should do the trick. Do your outputs provide ground or +12 volts when active?

 

id have to dbl check but i believe i can do a switched ground or switched +12 depending on how i configure the output

 

Yes, the light would come on with the key. Then once the car starts up, it would turn off. I don't think the inspectors count number of flashes or anything. Usually (on my car), they just start it up and wait for it to disappear, then they drive it around the block, put it on the sniffer and if the light doesn't come on, they're happy.

Lou

 

project89,

I was thinking about your problem today when it occurred to me that I have 30 Atmel microcontrollers left over from a project so I whipped up some code, dug thru some parts bins, and stuffed it all onto a breadboard. I think it will solve your problem nicely. There are six wires with the following connections:

Red: Connects to the switched 12 volt ignition source.
Black: Connects to chassis ground.
Orange: Connects to the SES lamp (wire from stock ECM).
Yellow: Connects to standalone ECM output (positive 5-18v) or ignition switch “start.”
Green: Connects to ground if using ignition switch as “run” signal.
White: Optionally connects to ALDL terminal B.

Here’s how it works: When you turn the ignition switch to “on,” the lamp will illuminate briefly then blink off then back on. If using the preferred mode of input, a +5-18v output from your standalone ECM, and the green wire is left disconnected, the light will turn off as soon as it receives the positive signal. It will remain off as long as the signal is present and will immediately turn back on with loss of signal. If using the ignition switch start (crank) as the run signal instead (the green wire must be connected to ground in this case), the lamp will illuminate, blink off then on, then remain on until the switch is turned to crank the engine. When the start signal is received, the lamp will continue to remain on for a very brief time then will turn off and remain off till the ignition switch is cycled off and on, even if the car dies. The former method most closely mimics a stock ECM.

If the white wire is (optionally) connected to the ALDL terminal B and terminals A and B are shorted and the ignition switch is turned to on, the diagnostic mode will be mimicked, i.e. start flashing a code 12. The timing is pretty close to factory and includes a longer pause between every third cycle. The flashing continues till the ignition is turned off.

If you PM me your address I will send you this prototype, gratis—assuming it survives the night flashing away, which I believe it will as it’s been going a few hours already.

 

holy crap thats awsome man ill send u a pm in a min,woulda responded earlier but i never recived a notice saying there were replys to this thread

 

It's a known issue, they've been working on it for months. Hopefully one day it will start working better.

I'm curious how this Atmel project works out. I used to play with these but haven't touched one in about 10 years.

Lou

 

why not just put the stock ecm in when you go for inspections? but it prolly wont run right then would it

 

car would deff not run right at all

 

My darn cable internet went out last night during a storm and just came back online. I guess I can't complain when it's free, so is extended basic cable but I never watch it because my DirecTV is much better.

Anyway, I just got your PM so I'll drop it in the mail tomorrow.

You might want to put it in an enclosure. With a little trimming it will fit into a Radio Shack 4x2x1 (270-1802).