Resolved 1990 ECU pin 15 5volts?

[kornmstr1]

I'm attempting to wire my LC-1 into my 1990 ECU.

First start DSMLink reads full lean. Impossible, the cars was still running. I cut the LC-1 connection and DSMLink still reads full lean, 5v. Okay, that's weird, I'll send it to ECMTuning to check my traces etc, in the mean time let's put in my other ECU. Same issue, DSMLink is reading full lean, 5v, for pin 15, with the wire cut.

My question is a two part.
Do the 90 ECU's have 5v constant at pin 15?
If not, what's the deal?

 

[steve]

As noted by ECMTuning the EGRTemp input (Pin 15) on a 1G ECU has a 10k pullup resistor inside the ECU. That's why you're seeing +5v on the pin.

ecuinputdata [ECMTuning - wiki]

www.ecmtuning.com

 

[kornmstr1]

I apologize in advance if this sounds dumb, how do I get an X series WB or an LC-1 to work with pin 15?

Is the buffer circuit integrated into either of those?
Do I need to change something in link to read correctly?

 

[dwb]

I apologize in advance if this sounds dumb, how do I get an X series WB or an LC-1 to work with pin 15?

Is the buffer circuit integrated into either of those?
Do I need to change something in link to read correctly?

For an AEM X series, I outlined this in my build thread here: https://www.dsmtuners.com/threads/1991-tsi-awd.540276/post-153906342

This is a 93 ECU, so not exactly the same as a 90 but should be pretty close.

TLDR:
AEM Red/12v to pin #107.
AEM black/ground to #106.
AEM white/analog 0.5v to #15 (EGR Temp).
AEM brown/analog sensor ground to #24 (ECU sensor ground)
ECMLink: Assign EGR Temp input pin to "AEM Analog Wideband gauge" then add corresponding field to captured and displayed values.

I'm not sure what a LC-1 would require, but ECMTuning.com should have this procedure detailed since that's their preferred WB.

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[curt-s]

I apologize in advance if this sounds dumb, how do I get an x series WB or an LC-1 to work with pin 15? Is the buffer circuit integrated into either of those? Do I need to change something in link to read correctly?

It's right in steve's link at the bottom. It involves an opamp and 1/4W 100ohm resistor.

I love how detailed they are

 

[1990TSIAWDTALON]

The 2371IP is alot EASIER to work with. If you can do SMT then that's a much smaller pkg tho!

 

[kornmstr1]

I've had my DSM for 20 years and am mechanically inclined. The last couple posts humbled me a bit.

So lets get this straight;
- Most wideband outputs to ECU are 0-5v
- Pin 15 has 5v INSIDE the ECU (as seen by DSMLink), due to a "10k pullup" (no clue what that is tbh)
- Wiring in a buffer circuit will fix this? Presumably by making the signal something the ECU can register?
- DSMLink will just work once I've done this and selected the correct input, or do I need to adjust parameters?

I apologize for necessitating a dumbing down to this level. I've never encountered this before and figured there would be way more documentation around a "common" WB install in regards to the buffer circuit.

 

[danl]

I've had my dsm for 20 years and am mechanically inclined. The last couple posts humbled me a bit.

So lets get this straight;
- most wideband outputs to ECU are 0-5v
- pin 15 has 5v INSIDE the ECU (as seen by ecmlink), due to a "10k pullup" (no clue what that is tbh)
- wiring in a buffer circuit will fix this? Presumably by making the signal something the ECU can register?
- DSMLink will just work once I've done this and selected the correct input, or do I need to adjust parameters?

I apologize for necessitating a dumbing down to this level. I've never encountered this before and figured there would be way more documentation around a "common" WB install in regards to the buffer circuit.

You got it.

The point of the buffer circuit is to make the wideband output stronger so it can better control the voltage seen at ECU pin 15. The pin is not floating because it is being pulled up to 5 volts DC by the 10,000 ohm internal resistor and the wideband output has to work against the pin wanting to be at 5v.

Your other option if you don't want the complexity of the buffer chip is to run the wideband into the ECU's narrowband input and configure ECMLink to use that for narrow band simulation. It will work without a buffer chip, you don't need to mount another sensor, and you can keep the EGR temp input open for logging something else.

 

[kornmstr1]

Well, that didn't work!

Pulled the LC-1 and installed an AEM X series 30-0300. Gauge is fully functional. ECMLink is not.

White wire to egrtemp pin, Brown to ECU sensor ground. Still reads 5 volts in ECMLink. I tried all AEM sensors in the list and they're all but one reading 18.00:1 and the oddball read 15.9:1 but never moved, gauge was reading 14.xx:1.

I'm missing something.
I've tried two different 90 ECUs
I've tried two different WB
ECMLink reads 5v in all scenarios.
I didn't try the buffer circuit but everything I've seen, the X series works without one.

Is the 90 ECU different and incompatible in some bizarre, obscure way?

I'm running SD so I may have a different input to try, I'm just annoyed at the moment.

 

[kornmstr1]

Update.

Wired the aem x series into pin 8 iat and changed the intake temp input pin assignment to all of the aem wb in the list and the displayed value never changes... still. My tach is a little jumpy now, so that's cool.

Does anybody have any insight as to is going on? I feel like this is a straightforward install.

I tried two ecus, two diff wb, two diff input pins. Why is my reading in link not responding.

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[dwb]

Are you disconnecting/reconnecting to the ECU each time you remap the sensor pin assignment?

 

[We're on Boost]

Wired the aem x series into pin 8 iat and changed the intake temp input pin assignment to all of the aem wb in the list and the displayed value never changes... still.

I think what I would do at this point is disconnect the white wire of your AEM, disconnect it from the ecu and read the voltage of the white wire with a regular multimeter that you know is working ok. The voltage on the white wire should agree with this table in the AEM install manual:

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For example, if your engine is warmed up and running nice at idle it should be in closed loop with the real AFR being in the mid 14's. That should be about 3 volts on the white wire.
Be super careful that you don't accidentally let the bare end of the white wire touch any ground when you do this.

Pin 15 has 5v INSIDE the ECU (as seen by DSMLink), due to a "10k pullup" (no clue what that is tbh)

I think it's like this. Could be wrong. This is the diagram given in the install sheet for the AEM AIT (air temp) sensor 30-2010 which is a thermistor. Our stock temp sensors are also thermistors as far as I know. A thermistor doesn't generate a voltage. It is a type of resistor that changes its resistance a lot with change in temperature. To use a thermistor, the ecu needs to measure the resistance of it. In other words the ecu has to function like an ohmmeter on that input. An ohmmeter does put out a small voltage.

In this AEM diagram, there in the box labeled "ECM" is your 5 volt source, and a "pull-up" resistor.
This makes sense to me for a circuit that is supposed to have a thermistor as the "Sensor".
Because if the ECM is measuring the voltage drop across the pull-up resistor, guess what, you've got an ohmmeter there.
But I think it's just in the way for a circuit that is going to be measuring the voltage from a sensor that has a voltage output like the wideband analog (white) wire.
But I'm a mechanical not an electrical, and I don't know much about what is inside our ecu. So there's that!

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[We're on Boost]

Here's another test you can do while you have the AEM white wire disconnected from the ecu.
This is a test to see if your IAT input (#8) in the ecu is reading accurately.
Basically, get a small 1.5 volt battery, like a AA or AAA cell. Something less than 5 volts.
Measure the voltage of this battery with your multimeter (Volts dc) with the battery not connected to anything.

Then connect the + nose of the battery to the wire that goes into pin #8. Actually get it set up so you can make this connection intermittently, wire touching the battery nose, or not, on/off.
Connect the negative end of the battery to any nearby metal that is grounded.
Then log that. With engine off, ignition on of course.
The idea is to look at the Wideband Raw Volts in the log. Not AFR. Raw volts.

When the battery is connected, the raw volts should be whatever you measured up in line 4, or very close.
When the battery is disconnected, the Raw should be about 4.7 volts. Probably not 5.0! What I see is 4.69 volts when I do this.

Take a look at this log where I did this test with 3 different battery lash-ups to get 3 different voltages.
I had 3.14 volts, 1.355 volts, and 1.511 volts, as measured initially on the batteries with my multimeter (line 4).
In the log I see them as RawLinWB and the volt numbers in the log are about 0.04 volts lower than what I got before with the multimeter.
Good enough.
Whenever I'm not touching the battery nose with my wire, the RawLinWB shows 4.69 volts.
Now that part is weird but that's how it works with some of these inputs. I don't know for sure which ones but this log of mine was done using the intake temp (IAT) pin.
One handy thing about it is that if you see a Raw voltage of about 4.7 on an input that isn't working right, it kind of tells you that either there is nothing connected to it, or a dead thing is connected to it (a thing with no output).

In this log, show RawLinWB and you can no-show everything else to make it more clear: