How the 4A-GE ECU works

[Harvey]

I have always been interested in electronics, it would be great for ecu's etc but a lot of it just goes over my head Maybe i should try and get some books and start reading up on it!

What you have done in your testing and prototypes seems great!

It just so happens that when i do get a AE86, i will want a 4agze in it But for the time being my immediate likely car will be aw11 4age, so if you do start looking into modifying the ecu in the new year i will be very interested.

[np303]

Would it be possible to find virgin OE MCUs and program them with updated change data if your just trying to correct for a some simple bolt ons with no real need for in-depth on the fly tuning?

I've also picked up a couple spare US ae86 ECU's. I've pulled the original MCU off in an attempt to read it with me SuperPro chip reader/writer I just picked up off ebay. I'm slowly trying to learn all this stuff.
I've yet to be able to read the data from the chip. I know it's a bit generic of a question, but what do I need to read the chip?

[domi]

Hey, any of you guys, the ones that are good with electronics and such, feel like doing a write-up for the low-IQ-people like myself and all the others that are oblivious to the fact or haven't had the chance to acknowledge it yet?
I'll pay you... a beer.... or several.... or a whole case, depending on the writeup XD

[firehawk]

np303 Wrote:Would it be possible to find virgin OE MCUs and program them with updated change data if your just trying to correct for a some simple bolt ons with no real need for in-depth on the fly tuning?

I've also picked up a couple spare US ae86 ECU's. I've pulled the original MCU off in an attempt to read it with me SuperPro chip reader/writer I just picked up off ebay. I'm slowly trying to learn all this stuff.
I've yet to be able to read the data from the chip. I know it's a bit generic of a question, but what do I need to read the chip?

The MCU used in the bigport 4A-GE ECU is a clone of the Motorola MC6801 which has a read-only program memory. The devices were manufactured pre-programmed at the factory, so no "blank" 6801s exist - they are actually known as 6803s and have the internal ROM disabled. The 6801 is able to execute code from an external EPROM but the pins which are used for address/data buses are already in use for I/O. The pins would need to be re-mapped to other pins in the modified program code and the piggyback board which connects to the original MCU's socket.

I don't think the chip reader is able to get anything off the MCU because it is not re- or even one time programmable and therefore has no facilities for reading, programming or verifying the internal ROM. Only way to dump the code would be to build a small board which runs the MCU in test mode (mode 0) and executes code from an external EPROM with a simple program that dumps the contents of the internal ROM via serial line. You'll also need to program a PLD to decode the address lines into the enable signal for the EPROM.

Here's a nice program that can be adapted for dumping the 4A-GE ECU program;

http://www.8052.com/forum/read.phtml?id=128146

I'm currently working on building a board for dumping the code off my ECU and disassembling it but since I have a lot of other work to do on my car, this is currently somewhat on hold.

[domi]

Excuse the offtopic, but seeing you guys know what you're talking about i'd like to ask something. I recenty discovered my check engine light is not wired or not working or both, so in order to see if there are error codes i'm trying to route an LED directly to the ECU, to see what's what.

http://club4ag.com/faq%20and%20tech_page..._4A-GE.jpg
Going by the abovementioned link and a hint from jamie i was going to try linking the anode of the LED to the 'W' terminal and the cathode to the car's body, but then the question if i need a fuse arose. Would i need one and if yes - what kind. The diode i have is 5mm, 60mW, 2.6V forward voltage at 10mA. The forward current is stated 3.0VDC on the package, but from what i remember from physics class current was supposed to be measured in Ampers..? I really have next to no knowledge about electronics, so i thought i'd ask before frying my ECU... The engine is the 20v Blacktop from an AE111, it has been wired by the previous owner, so i have no clue if the job's good, but the car has been running before i bought it and the issues i'm having right now are very much weird to me. I outlined the trouble i'm having here:
http://www.aeu86.org/viewtopic/domis-gen...ead/t/4478
I'm sorry for splitting off the already posted topic, but seeing as ECU-adepts are discussing here, that'd be my best chance at getting their attention :wink:

[jamiemirror]

Oooops man :-)
The "hint" was just pointing to "W" pin. Don't know if using LED is good idea or not - that's why I warned you to check and ask before fry your ECU.

[firehawk]

If I remember correctly, the W pin on the ECU gives out 1V and that's insufficient even for lighting up a LED. You'll need to use a simple switching transistor like a 2N2222 to control the +12V from battery to the lamp or LED. Connect the W-signal to the base of the transistor, +12V to the collector and the lamp or LED's anode to the emitter. Connect the other side of the lamp directly to ground, but use a current-limiting resistor between the cathode and ground if you're using a LED.

[domi]

Isn't the W terminal supposed to light up the LED on the cluster, the Check Engine Light itself? If it's 1V would it be able to? I'm just trying to replicate the CEL on a smaller scale and in a more inconvenient location
Seriously, though, if it's only 1V I can just go for a really small bulb [like the ones they used to let us bulgarians play with in school and light up with a 1.5V battery, just to keep us content in pseudo-physics class, however it was called in 2nd grade....] and some minor fuse or nothing in particular... Then i'll have an excuse not to care about anodes and cathodes

[JMR_AW11]

domi Wrote:Excuse the offtopic, but seeing you guys know what you're talking about i'd like to ask something. I recenty discovered my check engine light is not wired or not working or both, so in order to see if there are error codes i'm trying to route an LED directly to the ECU, to see what's what.

http://club4ag.com/faq%20and%20tech_page..._4A-GE.jpg
Going by the abovementioned link and a hint from jamie i was going to try linking the anode of the LED to the 'W' terminal and the cathode to the car's body, but then the question if i need a fuse arose. Would i need one and if yes - what kind. The diode i have is 5mm, 60mW, 2.6V forward voltage at 10mA. The forward current is stated 3.0VDC on the package, but from what i remember from physics class current was supposed to be measured in Ampers..? I really have next to no knowledge about electronics, so i thought i'd ask before frying my ECU... The engine is the 20v Blacktop from an AE111, it has been wired by the previous owner, so i have no clue if the job's good, but the car has been running before i bought it and the issues i'm having right now are very much weird to me. I outlined the trouble i'm having here:
http://www.aeu86.org/viewtopic/domis-gen...ead/t/4478
I'm sorry for splitting off the already posted topic, but seeing as ECU-adepts are discussing here, that'd be my best chance at getting their attention :wink:

AFAIK most W outputs are open collector so you would need the following circuit..

connect one end of a 1000 Ohm series resistor to +12V and connect the other end of the resistor to the LED anode.

Connect the LED cathode to W pin on the ECU.
That should work and it will pull about 12mA from the 12V with a really brightly lit LED... However, the W circuit also relies on a couple of specific ECU pins being grounded to chassis 0V.

This grounding happens normally with the stock wiring loom. Without these pins being grounded the W lamp cannot light.

Edit: Don't be tempted to miss out the resistor if you don't have one. The resistor limits the current through the LED. Without it you will destroy the LED and possibly the ECU transistor that switches the W lamp. You may even blow a fuse

[domi]

I actually have a resistor like that, but was setting up the circuit the other way around, as in anode to the W, cathode to a 1k resistor and then to the body and was damn unhappy when it did not work. Thanks a whole bunch, i hope that does the job. If worse comes to worse i'm trying it out on wednesday. Hopefully the ECU spits out a major malfunction otherwise i cannot begin to imagine what could be wrong.

Cheers!!!