ALDL data logging

[YakkoWarner]

You got Windows 10 to talk to the OBD1? I can not get WindALDL to communicate using windows 10

I'm using TunerPro RT because I was told getting WinALDL to work on Win10 was hit or miss. If you have the Moates cable you need to use the
FTDI driver for it.

I've monitored and logged the data stream on 10-15 minute drives and the TPS doesn't seem to have any odd or stray jumps. With pedal full up it is between 0.45 and 0.47. Watching the data clearly shows the IAC opening and closing to maintain a ~1000 RPM idle. I did the IAC reset procedure where you let it fully close with A-B jumpered, disconnect to keep it closed and set the base idle with the set screw - with the IAC fully closed I could get the idle down to around 250 RPM without stalling, any lower and the engine would starve out (which to me indicates there is no vacuum leak since the buterflies could close enough to kill the engine, and the IAC is closing all the way otherwise the bypass air would keep the engine running).

Coolant, MAP, TPS all seem to be in believable values, and it does go into closed loop according to the ALDL data.

I have the 7747 computer, but I think you have to remove the chip and use a reader of some sort to actually extract the bin programming from the chip, I didn't see any way to read it through the ALDL connection. And I don't have a chip reader or burner.

 

[Sgt Gus]

You got Windows 10 to talk to the OBD1? I can not get WindALDL to communicate using windows 10

I changed the baud rate from default to 4800 and started working, win 10 and winALDL

 

[chris3353]

i just snagged an sweet window XP from a old lady on marketplace for 40$.

I will keep it for the TBI only. I think she played Bingo on it.

 

[YakkoWarner]

Having had some more time to fiddle with and capture some data with this thing; I have now run into a couple things I do not understand:

1 - The 10K resistor does not do what I expected:

It does "something", but I can't figure out what. Suggestions from folks on here indicated that the 10K resistor was required across the A-B pins for data capture/logging. However, I have been able to capture/log data with and without the 10K resistor enabled. But, with the 10K resistor across the A-B pins, the computer behavior changes.

The obvious change that I can easily reproduce is that with the 10K enabled, the computer is dead set on forcing the idle to around 1000 RPM in all circumstances. I can watch the IAC counts go up and down as the truck is driven, and the IAC is absolutely opening and closing to hold a 1000 RPM idle. Shifting in and out of gear will also make the IAC step up or down to idle at 1000 RPM.

Without the 10K across the A-B pins, this does not happen. In gear the IAC seems to open and close to hold around 750 RPM, and shifting to neutral or park it causes it to do more or less does nothing - whatever the IAC count was when I shifted out of gear just stays fairly constant and the RPM goes up to 1000-1200, without the IAC doing anything to control it. On startup it will assert control but once the truck has been put in gear and comes back to park or neutral, it stops making adjustments until the truck goes back into gear, at which point it will again step up or down to hold 750 in gear.

A relevant note to this is that the base idle (IAC disconnected in the fully closed position) is around 500 RPM in park/neutral, so the IAC is controlling the idle speed. Also the truck "feels" like its running better with the 10K enabled - I cannot say exactly what, but it seems to have slightly more power and better throttle response?


2 - Open/closed loop doesn't seem logical:

While driving, the computer reports it is in closed loop. Right up until I lift from the pedal to slow down, at which point it instantly jumps to open loop and stays there while idling. As soon as the pedal is pressed even lightly, it jumps right back to closed loop and stays that way. TPS voltage is 0.53-0.55 with pedal not pressed and seems to stay constant. Sometimes with the 10K enabled it will go back to closed loop once the vehicle speed hit 0, sometimes not.

 

[chris3353]

Having had some more time to fiddle with and capture some data with this thing; I have now run into a couple things I do not understand:

1 - The 10K resistor does not do what I expected:

It does "something", but I can't figure out what. Suggestions from folks on here indicated that the 10K resistor was required across the A-B pins for data capture/logging. However, I have been able to capture/log data with and without the 10K resistor enabled. But, with the 10K resistor across the A-B pins, the computer behavior changes.

The obvious change that I can easily reproduce is that with the 10K enabled, the computer is dead set on forcing the idle to around 1000 RPM in all circumstances. I can watch the IAC counts go up and down as the truck is driven, and the IAC is absolutely opening and closing to hold a 1000 RPM idle. Shifting in and out of gear will also make the IAC step up or down to idle at 1000 RPM.

Without the 10K across the A-B pins, this does not happen. In gear the IAC seems to open and close to hold around 750 RPM, and shifting to neutral or park it causes it to do more or less does nothing - whatever the IAC count was when I shifted out of gear just stays fairly constant and the RPM goes up to 1000-1200, without the IAC doing anything to control it. On startup it will assert control but once the truck has been put in gear and comes back to park or neutral, it stops making adjustments until the truck goes back into gear, at which point it will again step up or down to hold 750 in gear.

A relevant note to this is that the base idle (IAC disconnected in the fully closed position) is around 500 RPM in park/neutral, so the IAC is controlling the idle speed. Also the truck "feels" like its running better with the 10K enabled - I cannot say exactly what, but it seems to have slightly more power and better throttle response?


2 - Open/closed loop doesn't seem logical:

While driving, the computer reports it is in closed loop. Right up until I lift from the pedal to slow down, at which point it instantly jumps to open loop and stays there while idling. As soon as the pedal is pressed even lightly, it jumps right back to closed loop and stays that way. TPS voltage is 0.53-0.55 with pedal not pressed and seems to stay constant. Sometimes with the 10K enabled it will go back to closed loop once the vehicle speed hit 0, sometimes not.

If you get data, do not worry about the 10k resistor/pins. I forgot which way i needed it to capture data but never noticed it affecting the engine RPM.

500 rpm should be close enough, you confirmed the IAC is raising the baseline.

the loop will open on Decel, normal behavior, TBI cuts off the fueling when certain parameters are met.


So the issue is it still wants 1000 RPM with the cable disconnected? are yo using WINALDL? or tuner pro? Can you screen shot the flag data tab of WINALDL or list any flags your getting? there is also a error code tab

 

[YakkoWarner]

If you get data, do not worry about the 10k resistor/pins. I forgot which way i needed it to capture data but never noticed it affecting the engine RPM.

500 rpm should be close enough, you confirmed the IAC is raising the baseline.

the loop will open on Decel, normal behavior, TBI cuts off the fueling when certain parameters are met.


So the issue is it still wants 1000 RPM with the cable disconnected? are yo using WINALDL? or tuner pro? Can you screen shot the flag data tab of WINALDL or list any flags your getting? there is also a error code tab

Well not exactly. Without the resistor it will give me idle@750 when in gear (drive or reverse) but seems to not really assert any control when in park or neutral. With the resistor it wants to idle@1000 under any circmstance. I'm using TunerPro RT - I have the laptop containing the log files with me here at work so it should have all the relevant data somewhere. Just may take me a while to figure out how to extract it.

 

[YakkoWarner]

If you get data, do not worry about the 10k resistor/pins. I forgot which way i needed it to capture data but never noticed it affecting the engine RPM.

500 rpm should be close enough, you confirmed the IAC is raising the baseline.

the loop will open on Decel, normal behavior, TBI cuts off the fueling when certain parameters are met.


So the issue is it still wants 1000 RPM with the cable disconnected? are yo using WINALDL? or tuner pro? Can you screen shot the flag data tab of WINALDL or list any flags your getting? there is also a error code tab

OK here are the relevant (hopefully) screen caps that show the measured parameters and the toggled flags. There is a LEAN error flag set, the ECU triggered the SES light with a lean code a couple weeks ago, but it did not come back on during this 10-ish mile test trip.

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I am not sure I put much faith in that MAP kPA reading, since 41.35 inches of manifold pressure would be a few PSI of boost which I certainly don't have. Likewise 0.55 volts of TPS doesn't actually seem like over 1/4 throttle, but the voltage should be right.

 

[Ricko1966]

When you short AandB it puts the ECM in service mode I'm assuming that's why it's changing your idle. The way I understood the resistor is your odd duck 94 95 cars when they had OBD 1.5 had to have the resistor to get the ECM to communicate with the cable.

 

[Fat 454]

In other news, - after a reasonable amount of online "research" - stumped up for this repro TEC 2 scanner. Wont do ALDL, but for later GM models. Specifically got this to read GM Holden codes for my boys rides. We'll see how it goes I guess. Will report back..

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[gmbellew]

MAP is absolute pressure. you need to subtract the value from atmospheric to get vacuum.

it should not go into open loop under decel. is the exhaust stock and is the O2 sensor in the driver side exhaust manifold?

some 454s went open loop at idle, but that wouldn't happen until the speedo was almost to 0mph.

the ECM stores codes for 30 or so starts. disconnect the battery cable to clear them.

I didnt think the 10k resistor was needed. it is putting the ECM in a diagnostic mode i think, like Ricko said above.

also make sure you are using the proper. adx file for the ECM.

 

[YakkoWarner]

MAP is absolute pressure. you need to subtract the value from atmospheric to get vacuum.

it should not go into open loop under decel. is the exhaust stock and is the O2 sensor in the driver side exhaust manifold?

some 454s went open loop at idle, but that wouldn't happen until the speedo was almost to 0mph.

the ECM stores codes for 30 or so starts. disconnect the battery cable to clear them.

I didnt think the 10k resistor was needed. it is putting the ECM in a diagnostic mode i think, like Ricko said above.

also make sure you are using the proper. adx file for the ECM.

I've got ADX files that say they are for the 1227747 computer. One of them was obviously not right because the reported coolant temp started at 300+ centigrade and came down as the engine warmed up...found and loaded a different file which seems to give mostly rational values. Apparently some of the values are calculated via an editable translation formula from the raw data (like the TPS percentage and MAP kPA) so whoever made the ADX file could have used the wrong math I guess. Not knowing enough about these things to know what expecte range for the raw data is means I'm kind of taking a leap of faith.


My O2 sensor is in the factory location (I'm still using factory manifolds, no headers or aftermarket performance stuff). The exhaust is not stock further back, it was split into a full dual system instead of both sides coming together into a single (done well before I bought the truck). Being in this part of the country it didn't surprise me much to see the cats missing before buying, they get stolen quite regularly here. Theres just some roughly welded pipe on both sides where they should have been, so it looks like whoever did the dual exhaust originally included them (and some drug addict got a payday from hacking them off because its an easy truck to get underneath). So technically the O2 sensor is only reading the 1-3-5-7 side of the engine.

As soon as I touch the accellerator pedal it jumps back into closed loop, but always goes open on decelleration. Sensor seems to be working, on a graphical plot of the data I can see the value fluctutaing and the system is registering/counting O2 crossings.

I had been told (even by a couple people here privately) that the 10K was needed to start the data tranmission, but that may not have been accurate information or it may apply to a different ECU model. There is a lot of variance in the information floating around concerning these ECUs and their data output. I am assuming that GM never released a definative guide to the ECUs and decoding their data, so people are effectively reverse engineering it. A copy of the underlying source code that actually runs these things would probably answer a lot of questions, but good luck finding that. The PROMs seem to store base lookup tables and default values, but I don't think even those contain the actual executable code that runs the computer.

 

[Ricko1966]

I've got ADX files that say they are for the 1227747 computer. One of them was obviously not right because the reported coolant temp started at 300+ centigrade and came down as the engine warmed up...found and loaded a different file which seems to give mostly rational values. Apparently some of the values are calculated via an editable translation formula from the raw data (like the TPS percentage and MAP kPA) so whoever made the ADX file could have used the wrong math I guess. Not knowing enough about these things to know what expecte range for the raw data is means I'm kind of taking a leap of faith.


My O2 sensor is in the factory location (I'm still using factory manifolds, no headers or aftermarket performance stuff). The exhaust is not stock further back, it was split into a full dual system instead of both sides coming together into a single (done well before I bought the truck). Being in this part of the country it didn't surprise me much to see the cats missing before buying, they get stolen quite regularly here. Theres just some roughly welded pipe on both sides where they should have been, so it looks like whoever did the dual exhaust originally included them (and some drug addict got a payday from hacking them off because its an easy truck to get underneath). So technically the O2 sensor is only reading the 1-3-5-7 side of the engine.

As soon as I touch the accellerator pedal it jumps back into closed loop, but always goes open on decelleration. Sensor seems to be working, on a graphical plot of the data I can see the value fluctutaing and the system is registering/counting O2 crossings.

I had been told (even by a couple people here privately) that the 10K was needed to start the data tranmission, but that may not have been accurate information or it may apply to a different ECU model. There is a lot of variance in the information floating around concerning these ECUs and their data output. I am assuming that GM never released a definative guide to the ECUs and decoding their data, so people are effectively reverse engineering it. A copy of the underlying source code that actually runs these things would probably answer a lot of questions, but good luck finding that. The PROMs seem to store base lookup tables and default values, but I don't think even those contain the actual executable code that runs the computer.

Where I got and get most of my info now,is on 3rd gen. Not a member I just browse,but 3rd gen is all 3rd gen Camaros lots more TBI Camaros then there are TBI Squarebody's. Also lots more guys trying to Mod TBI Camaros than TBI Squares.

 

[gmbellew]

Have you looked at your PROM to see if it is an OEM PROM? It should have a 4 digit code on the label you can see without removing it from the ECM. The switching to open loop on 0 throttle almost seems like somebody dropped in a tuned PROM to intentionally do that. As long as idles ok, it probably isn’t a big deal.

I asked about exhaust bc if the O2 gets too cold it will stop fluctuating and then the ECM reverts to open loop.

MAP kpa is a formula, but you should be able to check it with key on and engine off bc it should read atmospheric pressure.

The TPS % hack is based off an assumed value at idle of somewhere around 0.5v. I wouldn’t worry too much about it being off.

 

[YakkoWarner]

I'll try to see if I can get to the PROM ID number sometime over the long weekend coming up (won't be at an internet-enabled location until Monday at that point though). I had it out once when I replaced the ECU (I was chasing phantoms at that point) and everything looked undisturbed when I moved the chips to the new ECU but my memory is also unreliable).

The idle seems to stay around 750 when in drive or reverse, but goes up in neutral (and the IAC doesn't step down to take control at that point for some reason, even though I know it works because it will do so in drive or with the 10K resistor set).

 

[gmbellew]

I'll try to see if I can get to the PROM ID number sometime over the long weekend coming up (won't be at an internet-enabled location until Monday at that point though). I had it out once when I replaced the ECU (I was chasing phantoms at that point) and everything looked undisturbed when I moved the chips to the new ECU but my memory is also unreliable).

The idle seems to stay around 750 when in drive or reverse, but goes up in neutral (and the IAC doesn't step down to take control at that point for some reason, even though I know it works because it will do so in drive or with the 10K resistor set).

Idle will be higher in P/N. To me it sounds like somebody has modified the tune to bump the idle target, especially if the IAC seems to be moving around to maintain it. Mine is bumped to idle around 650-675 in gear and is probably around 850 in P/N. IAC counts don’t usually move much from park to gear, so with less load on the engine the idle goes up. And if the PROM is a tune, I’d wager that somebody also also modified the open/closed loop logic.

Edit - I see you have a 454. I am more familiar with 350. Some of the 454 had open loop idle as a factory tune. Also 454 idle speed target is 750rpm in drive fully warmed up and idle is open loop. This is all in the emissions and drivability manual. Sounds like you don’t have an issue to me with idle control via the computer