Losing connection when datalogging

[joshwilson3]

Does anyone have problems with losing connection with the ECM when datalogging? What will happen is the data will stop flowing while running a scan. It happens frequently where it can lose connection after only a few minutes of starting the datalog. You have to restart the car and reboot the laptop everytime it happens. As for some reason when this happens, after shutting the car down and turning the key "on". You can't get a connection, even after restarting Tunerpro RT or Datamaster. So you have to reboot the laptop, open Tunerpro RT or Datamaster. Then you can get a connection.

I had read some talk about it has something to do with the ECM used in the late 80's and maybe also early 90's Vettes. But I don't think it is usually frequent.

I'm using a Moates cable.

 

[Hib Halverson]

I'm not familiar with "Tunerpro RT" but I have used "Datamaster".

When using Datamaster I've never experienced the problem you have, however, I'm connecting to a 95 ECM and you're connecting to an 89 ECM.

As for the rumor you're heard about 80s and the 89 ECM...they are not the same, so it's unlikely what you heard is correct.

There is one issue of which I'm aware that affects only the ECMs used on F-car and Corvette in model years 86-89 and it has to do with some peculiarities of the communications protocol used in those years. I don't know enough about the specifics of this to explain it more and because I've never had a problem with it, I've never explored it.

I'd contact the publisher of Datamaster. Maybe he can help you. Also, you might try contacting the cable maker and see if they have any information. I suggest that because the way the TECH1, TECH1A and Mastertech scan testers addressed the issue was with an "adapter" (known as the "Pin E Adapter") that was installed between the MIL connector of the vehicle and the MIL connector on the tester's cable.

 

[joshwilson3]

I'm not familiar with "Tunerpro RT" but I have used "Datamaster".

When using Datamaster I've never experienced the problem you have, however, I'm connecting to a 95 ECM and you're connecting to an 89 ECM.

As for the rumor you're heard about 80s and the 89 ECM...they are not the same, so it's unlikely what you heard is correct.

There is one issue of which I'm aware that affects only the ECMs used on F-car and Corvette in model years 86-89 and it has to do with some peculiarities of the communications protocol used in those years. I don't know enough about the specifics of this to explain it more and because I've never had a problem with it, I've never explored it.

I'd contact the publisher of Datamaster. Maybe he can help you. Also, you might try contacting the cable maker and see if they have any information. I suggest that because the way the TECH1, TECH1A and Mastertech scan testers addressed the issue was with an "adapter" (known as the "Pin E Adapter") that was installed between the MIL connector of the vehicle and the MIL connector on the tester's cable.

I was referring to late 80's i.e. 86-89.

It happens on both Tunerpro RT and Datamaster. I did talk to Moates, but he said it had to do with the ECM that is used in the Vettes. And he had said I should be able to just shut the car off then back on then reconnect. But that doesn't work as you have to reboot the laptop, then relaunch the software to then get a connection.

 

[TedC]

Are you seeing any other serial data related issues? Such as odd MPG readings on the cluster or up shift light turning on if you have an automatic? The serial data circuit can fail on L98 ECMs and the engine will still run fine. This happened to me on my 1989. Double check your connection to the diagnostic port and work the serial wire back to the ECM. If I remember correctly, a resistor is needed to force the ECM into the right testing mode. Make sure that connection is working properly if required as well.

Side comment: When you open up these ECMs, you will find a circuit board that is clear coated with a material called a conformal coating. With age, this coating can create odd electrical issues, especially in areas that run hot. It is cheaper to replace the ECM with a rebuilt than taking the time and energy to isolate the issue. The rebuilt ECM should have a nice new conformal coating.

 

[TedC]

Another suggestion. Check your port setting on your PC. What is the data rate? These ECMs do not support very fast serial data rates. Some PC serial ports will auto adjust, others do not.

 

[TedC]

When I had this working on my PC, I was using a RS-232 PC Card. Here are the setting I used.

 

[joshwilson3]

Are you seeing any other serial data related issues? Such as odd MPG readings on the cluster or up shift light turning on if you have an automatic? The serial data circuit can fail on L98 ECMs and the engine will still run fine. This happened to me on my 1989. Double check your connection to the diagnostic port and work the serial wire back to the ECM. If I remember correctly, a resistor is needed to force the ECM into the right testing mode. Make sure that connection is working properly if required as well.

Side comment: When you open up these ECMs, you will find a circuit board that is clear coated with a material called a conformal coating. With age, this coating can create odd electrical issues, especially in areas that run hot. It is cheaper to replace the ECM with a rebuilt than taking the time and energy to isolate the issue. The rebuilt ECM should have a nice new conformal coating.

I don't have any problems other than running lean and getting knock counts on acceleration after the engine has warmed up.

Where is the serial data circuit?

Yes, you need to turn on the 10k resistor to start the data flowing. Once the data is flowing you can turn off the 10k resistor. As with it left on, it can scew your data. Though I also tried leaving the 10k resistor on, but it didn't solve the problem.

Everything should be connected up fine when I connect the cable to the ALDL and connect the other end to my laptop.

The ECM in my 89 is a rebuilt by General Motors. When I had it out last, I didn't notice anything odd on the board. The coating looked nice and shiny.

I did adjust the latency to 1 as was instructed in the manual.

 

[TedC]

Please report back if your MPG cluster readings look OK. The cluster displays serial data output from the ECM. This info will help you determine if the ECM serial data processing circuit is messed up, or if this is an isolated issue with connectivity/compatibility with the serial data cable/logger. The serial data processing circuit is integrated into the ECM motherboard. My defective ECM board looks brand new as well, so don't go by appearance. The time and energy to probe the ECM board is not cost effective and requires special equipment. Replacement cost was < $100. I bench tested the "defective" board with a "working" ECM and the serial output line was dead using an Oscilloscope. If your MPG readings look fine (resets OK and actual MPGs are correct), then you have a connectivity/compatibility issue. I would also suggest trying another PC. Not all serial ports are the same (different chip sets and drivers).

 

[joshwilson3]

Please report back if your MPG cluster readings look OK. The cluster displays serial data output from the ECM. This info will help you determine if the ECM serial data processing circuit is messed up, or if this is an isolated issue with connectivity/compatibility with the serial data cable/logger. The serial data processing circuit is integrated into the ECM motherboard. My defective ECM board looks brand new as well, so don't go by appearance. The time and energy to probe the ECM board is not cost effective and requires special equipment. Replacement cost was < $100. I bench tested the "defective" board with a "working" ECM and the serial output line was dead using an Oscilloscope. If your MPG readings look fine (resets OK and actual MPGs are correct), then you have a connectivity/compatibility issue. I would also suggest trying another PC. Not all serial ports are the same (different chip sets and drivers).

When you talk about the MPG cluster readings. Is that while datalogging, or just in normal driving? I know while datalogging, some of that stuff is messed up like I believe the MPG readings. I don't recall exactly which readings are messed up while datalogging, but I've read from others that some of those things mess up while datalogging. But in normal driving, the MPG appears to work fine. And it resets fine in normal driving.

On my laptop, I'm using a USB cable on the Moates ALDL cable.

Moates have given me some ideas. He says when the data stops flowing, that I should be able to shut the car off for 10 seconds, then turn it to "on" and get the data flowing again without having to reboot the laptop. If that don't work. He said to unplug then replug the USB cable to see if the data starts flowing. If it does, then that could mean I'd need to get a Ferrite USB as it could be interference or the Moates device/cable could be bad. In which I could swap it out with another to see if that fixed it.

 

[TedC]

ECM produces and outputs serial data. This serial data is transmitted 1 byte at a time over a single wire. Transmit speed is pretty slow. This serial wire connects to the cluster, then to the diagnostic port. It is real easy to determine if the ECM is transmitting serial data. Just check the range function and average fuel usage display on the cluster. Cluster depends on ECM serial data for these functions to work properly. Make sure these work properly without any device attached to diagnostic port. I don't remember my AutoXray ever messing up these functions, but it is possible. If your data logger works, then stops, this sounds like a connectivity/compatibility issue. OBD I specifications are not all that well defined. I've seen new dual purpose OBD I/II scanners fail to connect to these older ECMs. Play around with your PC port settings (speed and buffering), and make sure the COMx port assigned is not shared with other devices.

 

[vetteboy86]

I've never had any issues with Datamaster while scanning my 86. I've probably performed 500 scans with no issues. Are you using the free version, or did you pay for unlimited scans?

You may try reloading the software. The ALDL cable you have, is it true usb, or are you using an USB to RS232 converter to plug into your laptop? Have you changed ports that you are using? I have noticed that when I first began, I had to have the ALDL cable plugged into my computer before starting Datamaster. The fact that you can't simply reconnect without restarting your computer makes me believe it is software related.

 

[joshwilson3]

I've never had any issues with Datamaster while scanning my 86. I've probably performed 500 scans with no issues. Are you using the free version, or did you pay for unlimited scans?

You may try reloading the software. The ALDL cable you have, is it true usb, or are you using an USB to RS232 converter to plug into your laptop? Have you changed ports that you are using? I have noticed that when I first began, I had to have the ALDL cable plugged into my computer before starting Datamaster. The fact that you can't simply reconnect without restarting your computer makes me believe it is software related.

It's done it both on Tunerpro RT and Datamaster. I've got the trial version of Datamaster right now.

The ALDL cable I have is Moates:

ALDU1 and CABL1 XtremeALDL and NewCABL1 Combo [ALDU1_CABL1] - $80.00 : Moates.Net

Moates suggested to leave the car off for more than 10 seconds when the data stops flowing. He said if you don't, then you might not can reconnect. Or he said if there is interference, then that might not let you reconnect either. And suggested trying to unplug and replug the USB cable to see if it will reconnect.

I could try next time with another port. There are two.