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Old 07-03-2018, 02:50 PM   #1
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Anybody know SR20DET ECU well?

I am currently re-wiring my S13, both body and engine harness. As I look over schematics again and again I start to wonder things. Maybe someone here knows about this stuff...

I have a 62 SR20DET ECU for reference.

- what does the ECU do with input from speedometer?
- ECU Pin 24: Malfunction Indicator Lamp. My understanding has always been that these ECU's don't have the ability to output to CEL. Does this pin function?
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Old 07-03-2018, 03:05 PM   #2
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Often times the speed is used for speed limiter/cut, launch control if you have a modified ECU, or when the ECU decides to go from closed loop to open loop (some ECUS like KA ).

Often times that would result in a CEL if your ECU supports that malfunction.

Also, the only way a CEL is lit up is Via output from the ECU. The ECU drives the light on when it detects an error
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Old 07-03-2018, 03:27 PM   #3
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So the root of my speed sensor question is why should I keep it? what does it do for me? I run a mild setup, stock ecu, no launch control.

Quote:
Originally Posted by Ilya View Post
The ECU drives the light on when it detects an error
Right, so what I am asking is, can SR20DET 62 ECU do this?

I have always been under the impression it cannot.

If the answer is yes, does that terminal on the ECU switch to ground or +12v?
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Old 07-03-2018, 03:49 PM   #4
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Download nistune and open an n62 bin and check to see if there are maps or constants based on speed.
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Old 07-03-2018, 09:51 PM   #5
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The ECU uses vehicle speed, RPM and MAF voltage to do a variety of things, mainly in-gear rev limit, speed limit, OL and CL fueling and also to put itself into the "upper gear" fuel/timing maps (Nistune). Put it this way, if it didn't need this input from factory, it wouldn't be there. I'd recommend keeping it, but that's just my $0.02

As for the MIL, the ECU can and does trigger the MIL under very few, and rare circumstances. Does this really matter? Not 100%, however I'd still recommend getting it working as it can do a lot of things more easily, like check code blinks, OR, if you use a stand-alone, you can select to use the MIL as a knock light, among other things, which is really handy.
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Old 07-03-2018, 10:33 PM   #6
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I've never even seen an mil go on in any car. Except my most recently one because I programmed it to go on when trans temp > 190*F but thats another thing.

My point being the 62 ecu is so simple you really don't need an MIL for the majority of the time, there are only like 2 parts that can really cause major issues on (89-02) sr20 swaps. (maf and ecu typically the only two annoying bad items and both are rare) the rest of the stuff is super easy from basic intuition. such as knowing the cas trigger the fuel relay when you turn the motor by hand slightly thus verifying at least the optical pickup inside is good. Then checking the timing pulls the entire ignition system into question with one simple, a mandatory test anyways. compression is done via compression test. Then fuel pressure test is the fuel side.

All thats left is the maf and ecu as potential carriers. TPS and O2 are not important and won't screw you if they are bad or missing. And through the spark / timing test you verified the pickup(cas) and optical unit (cas). So whats left to throw a code for? There is like literally nothing besides a maf code or "ecu code" (no response from computer at all) that I could think of as being useful, and by process of elimination we can tell that the computer is turning on, leaving only the maf.

Most sr20 problems aren't in the computer/MIL side of things anyways. In a swap the #1 overlooked and #1 most important thing is a boost leak pressure test.
Do this to every car, every single time. No excuses. If the air is leaking out, besides screwing the maf and potentially washing your oil with fuel, enough of a boost leak will cause a high exhaust gas pressure and high IAT which will lead to engine destruction.
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Old 07-05-2018, 06:46 AM   #7
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Thanks guys, good to see theres a few people around here interested in this type of detail.

Quote:
Originally Posted by Ilya View Post
Download nistune and open an n62 bin and check to see if there are maps or constants based on speed.
I have an ECUTalk cable, and had some sorta software on an old computer [been gone a few years so I forget]. I'll have to look into this.

Can you elaborate on 'N62 bin', what does that refer to?

Quote:
Originally Posted by ARC240 View Post
..if it didn't need this input from factory, it wouldn't be there.

As for the MIL, the ECU can and does trigger the MIL under very few, and rare circumstances.
I agree entirely with speed sensor comment, I am just trying to better understand the 'logic' the ECU uses it for.

I still have to get to the ECU and turn the screw...so it's easy enough to watch the blinking light there.


Quote:
Originally Posted by Kingtal0n View Post
My point being the 62 ecu is so simple you really don't need an MIL for the majority of the time....
Agreed. Especially if you are 'one with the motor', its easy to tell when things aren't right. I don't need a light bulb to inform me.

I've read many times that 'SR20's dont have a check engine light' and if you look at the ECU pinout there is clearly a terminal for MIL...can't trust these damn kids on Zilvia.
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Old 07-05-2018, 07:02 AM   #8
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Quote:
Originally Posted by KoukiMonsta View Post

I've read many times that 'SR20's dont have a check engine light' and if you look at the ECU pinout there is clearly a terminal for MIL...can't trust these damn kids on Zilvia.
That's a load of bs. You're right that they do, so trust yourself 100% in believing there is. They definitely do have a MIL, just OBD1 is one hell of a lot more lenient when it comes to triggering a MIL. I've seen a lot of completely failed parts (MAF, CAS, coils, injectors, temp sensors, knock sensors and failed boards themselves, etc) on every thing from R32s, S13/14/15 and Z32 where the ECUs haven't bothered triggering the MIL, but something was most obviously awry.

The older ECUs are very very basic compared to the newer ones. Most of the ECUs that run the older engines have very limited sensor threashold tables for determining faults within a sensor itself through feedback voltages, so they're restricted in what they can do and detect, thus the MIL on being a rare sight.
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Old 07-05-2018, 12:21 PM   #9
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Another question -

Fuel pump signal from ECU, does this switch to ground or provide +12v?

Does 62 ECU prime fuel pump for 2 seconds when key is in ON position?
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Old 07-05-2018, 06:07 PM   #10
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Quote:
Originally Posted by KoukiMonsta View Post
I have an ECUTalk cable, and had some sorta software on an old computer [been gone a few years so I forget]. I'll have to look into this.

Can you elaborate on 'N62 bin', what does that refer to?
If you download Nistune Trial version, and can connect to the ECU to get the ECU#, you will know which file to open in Nistune. Otherwise you can try to cross reference external markings of the ECU to the available BINs supplied by Nistune.

Nistune supplies you with BINs (memory dumped into a file from the ECU) for various ECUs. Once you know the ECU#, open the correct bin file in Nistune, Nistune will be able to show you all values you have questions for, as the software is able to take the bin file from an ECU and display most of the data graphically.

In there you will find parameters that define things like:
-"Speed at which Closed Loop Works"
-"what speed to do decel fuel recovery"
-"Speed Limiter"
-"HOW LONG THE FUEL PUMP PRIMES WHEN IGNITION IS TURNED ON"
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Old 07-06-2018, 07:19 AM   #11
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Quote:
Originally Posted by Ilya View Post
If you download Nistune Trial version, and can connect to the ECU to get the ECU#, you will know which file to open in Nistune. Otherwise you can try to cross reference external markings of the ECU to the available BINs supplied by Nistune.

Nistune supplies you with BINs (memory dumped into a file from the ECU) for various ECUs. Once you know the ECU#, open the correct bin file in Nistune, Nistune will be able to show you all values you have questions for, as the software is able to take the bin file from an ECU and display most of the data graphically.

In there you will find parameters that define things like:
-"Speed at which Closed Loop Works"
-"what speed to do decel fuel recovery"
-"Speed Limiter"
-"HOW LONG THE FUEL PUMP PRIMES WHEN IGNITION IS TURNED ON"
No Shit, I'll have a look.

But does ECU ground the fuel pump terminal or nah?
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Old 07-06-2018, 11:40 AM   #12
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If you open this page:

http://www.240edge.com/manuals/s14_sr20det.pdf

This is a Factory Service Manual for an S14 SR20 which is almost identical to S13.

Flip to page EC-11. Follow ECU Pin 18 to get your answer. If you still need help, report back.
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Old 07-06-2018, 11:59 AM   #13
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I used to think all factory ECU ground a pin for turning things on and off. It just seemed safer.

But one day I ran into a computer that was throwing 12v. so they can do either.

I don't recall which the factory ecu does but it isn't difficult to test with a $5 multi meter from Harbor freight. Also you can easily reverse the order by using another relay. Since most fuel pump high performance installs need larger 12v wires anyways, its fairly common to use the existing fuel pump 12V feed wire to simple trigger a relay near the pump that pulls on a much larger 12v wire to feed the actual pump.
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Old 07-06-2018, 12:45 PM   #14
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Quote:
Originally Posted by Ilya View Post
Flip to page EC-11. Follow ECU Pin 18 to get your answer. If you still need help, report back.
Thanks for spoon feeding me. I sit here and tell assholes to get the FSM out all day long, damn I'm a hypocrite.

Quote:
Originally Posted by Kingtal0n View Post
I used to think all factory ECU ground a pin for turning things on and off. It just seemed safer
yep, that was my assumption [FSM has proven me correct]. I have zero OEM wiring so this will get its own circuit, no need for extra relays.

But I have this super sweet engine harness test-O-matic setup right now in my living room and I wasn't getting continuity between the fuel pump pin and harness ground...so I added that question to my thread.

granted I was expecting it to ground/show continuity during priming cycle after I powered up the ECU, and I got nothing. I might have overlooked something with my test.

Im trying to continuity check everything before I throw it in the car, build confidence that my wiring will work.
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Old 07-06-2018, 02:36 PM   #15
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Quote:
Originally Posted by Kingtal0n View Post
I used to think all factory ECU ground a pin for turning things on and off. It just seemed safer.

But one day I ran into a computer that was throwing 12v. so they can do either.

I don't recall which the factory ecu does but it isn't difficult to test with a $5 multi meter from Harbor freight. Also you can easily reverse the order by using another relay. Since most fuel pump high performance installs need larger 12v wires anyways, its fairly common to use the existing fuel pump 12V feed wire to simple trigger a relay near the pump that pulls on a much larger 12v wire to feed the actual pump.
The best way to tell is to not use a cheap multimeter but to look at a schematic.

Your ECU might function one way but the relay it switches might be a NC or NO (Normally Closed until energized, or Normally Open until energized) and your multimeter test will just confuse you.

Unless its a 5W lighbulb, its best to switch everything through a relay, especially devices that generate EMF such as starters, alternators, and Fuel Pumps.
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