long (stupid) story, i've got an FC with an REW engine and ecu in it, and i would like to get the check engine light to work.

the FC ecu uses pin 1F, just like the FD, for the diagnostic port in the engine bay, and it works fine with the LED.

the FC uses pin 1E on the ecu to drive the actual check engine light bulb, in concept it works just like 1F.

the FD ecu pin 1F won't drive the bulb itself, although it does drive an LED just fine

the FD takes the pin 1F, and then it goes into the E/L unit, where some kind of magic occurs and then as if by magic the bulb in the cluster is driven.

so what does the e/l unit do? it seems like i may be able to switch to an LED, which would work.

has anyone had an E/L unit apart? i've searched, but info is scarce

 

It's the Electrical Load unit. It's kind of a weird box that they added in US cars, I don't believe it's on JDM cars.

Get a PowerFC and you ain't gotta worry .

Dale

 

How do you know that the FD ECU doesn't just switch a transistor inside the E/L unit which then switches 12V (or ground, whatever it needs) to the bulb?

Will the output from the ECU drive the coil on a relay?

 

that actually sounds like that is what it might do, i don't have an E/L unit to check though, and i was hoping someone would have pulled one apart...

the ECU will drive an LED, so it might be able to drive a relay. in the meantime i think i'm going to cheat and use the exhaust overheat output (pin 1V).

 

Here's what the EL unit does:

The EL (electrical load) unit sinks current from the corresponding ECU pin in response to the various electrical loads that are active, as input to the EL unit.

Another way to look at it is that EL unit presents a variable resistance to its respective ECU pin that corresponds to active electrical loads (allowing the ECU to compensate).

The current flow through the EL unit from the ECU pin seems to affect the ECU's idle control loop gain and perhaps the idle mixture or map as well. In any event, if you add a ~5k resistor from the subject ecu pin to ground (in parallel with the EL unit), it seems to help idle stability if you have a significantly ported engine. Note that this is not hearsay, I've actually tested this stuff.

Do not use the ECU's EL output pin as a voltage source for external components as you will experience unintended consequences. It's current limited anyway and of no particular use other than its intended purpose. If you want to delete the EL box, then substitute in a fixed resistor from the EL's ECU pin to Ground (in lieu of the EL box). Resistor will want to be in the range from about 1k --> 10k; pick a value that gives the best idle result.

Hope this helps!

 

the E/L does two things, the first is like you say, it takes the headlight, blower and TNS signals, which are separate inputs on the JDM car, and puts them to 1 pin, as the US eCu needs the other pins for the EGR (solenoid and switch), the AWS, and the other solenoid on the EGR valve.

the second thing it does, is take the error code signal, and do something to it to actually drive a light bulb.

i'm actually using a JDM eCu so i don't care about the first bit, but in CA i do need a CEL...

is the E/L unit the most durable part of the car? apparently its never failed?

 

I've never seen one die

 

i don't think i have either, and i've seen the body break, the hood, and the dash, and well its faster to list the stuff i haven't seen fail, the drive shaft, hood hinges... and apparently the E/L unit