Testing Your ECM While You Wait (Page 1/1)
Romsk NOV 21, 06:15 PM
All,

I am designing a bench test for stock Fiero GT ECMs (ECUs). I will be posting schematics and Arduino code on my web page, but since it is a large design, most people probably will not want to built their own.

I am a retired test engineer, so something like this is my specialty. I don't mind building it because I offer free diagnostic consultations to my ALDL Adapter users. It keeps me busy in my retirement and I enjoy it. What I am planning is this:

I can test ECUs for free as I don't expect to have many requests. But, the user will have to pay for shipping/insurance to/from me (both ways) in New Hampshire USA... the testing and report is free. I expect a one day turn around. I won't be able to test ECUs with aftermarket/performance EEPROMs.

If you go to the bottom of my web page (see below), you will see a concept of what I propose to build. The test fixture will also use the data from the ALDL link using my existing ALDL Monitor GUI for comprehensive test coverage.

https://paul.romsky.com/ind..._gt_aldl_monitor.htm

If I get enough people that would consider this, I will start building the tester.
It will be a 100% functional end to end test under real load, stimulus, and timing conditions.

At first I may not be able to repair failing ECUs because many components are now obsolete, but some repairs may be possible.

Let me know.

Thanks,
Paul
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Paul Romsky

[This message has been edited by Romsk (edited 11-21-2024).]

Vintage-Nut NOV 22, 12:15 PM
For your informational purposes only.....

I had 'weird problems' with a 1992 ECM in a different vehicle {not Fiero}, so I sent my computer to ECU Exchange for testing.

They found a bad power supply which created distortion on the reference voltages.

They repaired it; I got it back; installed the computer and the vehicle runs great now......

The Grand Total for the Repair?

Around $140 including shipping from Cailfornia to Florida

Merely my input,
VN

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Original Owner of a Silver '88 GT
Under 'Production Refurbishment' @ 136k Miles

Romsk NOV 22, 02:18 PM
Thanks for your input.
If I can get schematics and parts, I could also repair them.

$140 including shipping is not bad. I might not be able to compete with that as I was just providing test to verify if an ECU is working or not. They rarely go bad, I just wanted to give people peace of mind the ECU if good or bad as it can be a big unknown until you rule it out.

I am going to build my tester anyway - it looks like a fun project. I just ordered Pogo Pins. The idea is to slide the ECU into a fixture, the pogo pins (with cup tips) make contact without having to plug in/unplug connectors. This is common method in production testing.

My brother teaches automotive technology. He said he would like to show it to his students as it demonstrates how sensors are used in modern engines. The Fiero is a good example as it is fairly simple compared to ECUs today.

Paul
Dennis LaGrua NOV 22, 02:51 PM
While building an ECM tester is certainly possible the tester would need to simulate and vary all sensor inputs and all read ECM outputs; not an easy task. You would also need to have multiple connectors and a switching for the power, grounds. pin assignments and engine / trans simulation for the ECM being tested. A simple way might be to just measure for static reset but its above what I wish to do.. I'll just rely on scans while driving but good luck with the project.

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" THE BLACK PARALYZER" -87GT 3800SC Series III engine, custom ZZP /Frozen Boost Intercooler setup, 3.4" Pulley, Northstar TB, LS1 MAF, 3" Spintech/Hedman Exhaust, P-log Manifold, Autolite 104's, MSD wires, Custom CAI, 4T65eHD w. custom axles, Champion Radiator, S10 Brake Booster, HP Tuners VCM Suite.
"THE COLUSSUS"
87GT - ALL OUT 3.4L Turbocharged engine, Garrett Hybrid Turbo, MSD ign., modified TH125H
" ON THE LOOSE WITHOUT THE JUICE "

Romsk NOV 22, 09:41 PM
Since I have designed my Fiero ALDL Monitor, (Adapter and GUI), I have learned about the finer details on all the sensors, actuators, the ALDL Data, and the ECU.

I will be using an Arduio DUE to simulate the car side of the system. I don't need actual sensors and actuators, just simulated loads and stimuli. This is common practice in engineering testing. The tester is set up to actuate every pin and test the overall (end to end, Hardware In The Loop) functions of the ECU in real time. This is called an Acceptance Test Procedure (ATP).

The Test Panel can work in Manual or Automatic modes.

In Manual modes: I set the ALDL link to DMALDL Mode, turn on the ECU, set the EST circuit to not send timing pulses (Ignition on, Engine not running) then turn the following knobs and watch their respective responses on the ALDL Monitor GUI.
TPS, VSS, MAP, IAT, CTS, and O2. Then set the ALDL link to DMDIAG Mode, watch the SES for Error Codes and the GUI for Error Flags, then watch the IAC signals Home it to its fully closed position and then open after leaving DMDIAG Mode.

In Automatic modes, the Arduino does all that in real time by measuring the Injector pulses, MAP, IAT, CTS, and TPS. It then sends ICM (RPM) and VSS pulses. Then it can simulate the O2 voltage based on the constant AFR adjustments from those values. It can then monitor and simulate the EGR system and simulate it's responses as changes in the Engine RPM. It can simulate the Air Conditioning going on and off and see how the ECU responds. All the while not only monitoring the ALDL Data, but recording it for playback/comparison later. I can then put the ALDL Mode to DMFACT and see how the ECU handles Limp Home Mode.

This covers all the ECU Sub Sytems:
Power/Voltage/Reference/Grounds
Fuel Pump
Injectors
Ignition Subsystem (Electronic Spark Timing)
Throttle
Vehicle Speed
Manifold Absolute Pressure
Temperature (Intake Air Temperature (aka Mainfold Air Temperature)/Coolant Temperature)
Idle Air Control
O2 Sensor
EGR Subsystem
Transmission (Shift/Torque Converter Control/Park-Neutral)
Indicators (Service Engine Soon/Shift)
Air Conditioner Compressor Control
Diagnostic Link (including monitoring ALDL Data Frames that indicate how the ECU is working internally to control the Engine)

I have it all in my head, now I have to build, code, and integrate it with my old ECU.

See bottom of my page for the overall Setup and the Test Panel:

Romsky's Fiero Testing

[This message has been edited by Romsk (edited 11-22-2024).]

Aaron B NOV 26, 04:55 PM
I'm intrigued! This is the very reason I decided to migrate away from the factory ecu, ....I wanted to eliminate the possibility of it being the cause of my Fiero's erratic "run" personality. I am the third owner of the car that has embraced this challenge, and I have put on about 200 successful driving miles with the car on our back country roads so far. ( This is operating on the Holley Sniper system ).
I will read up on your website, ..nice work! I have a very close friend that designs and tests boards too, ...I have machined a few G10 (fibreglass) test boards for pogo pin installation per his drawings, ...neat stuff!!


Aaron
Romsk NOV 26, 08:22 PM
Aaron, I am still in the parts gathering phase. Digikey is getting expensive. I found really cheap parts on Amazon (from China of course) and some won't arrive until January. I sill have two others to find. So far it's $87 USD for parts. I already have an Arduino DUE on hand.

I am going to mount it all using my low cost control panel idea. See my YouTube video:
https://youtu.be/9ctittajlDQ?si=xxygNvXcf77cFA5g

I am only building one tester and not selling it, so cheap short infant mortality parts are OK with me.

Check back in February or drop me an email (see home page on my site) and I can send you an update when I get it going.
Aaron B NOV 27, 01:53 PM
Very good, ..good luck! I will keep an eye on your progress!

Aaron