Long saga of ECU problems or seemly ECU problems. My 2000 VDP has a weird recent history of what may be ECU problems.
In January 2015 while driving on a freeway in North GA, the car suddenly made a loud clunk sound, and the display started to show, "Gear Box Failure" "Engine fail safe Mode", and something else. I pulled off the road and turned the key to the OFF position. After about 15-20 seconds, I turned the key back on and the car started and drove just fine. Since that time the car intermittently has a similar failure. It will eventually start and run like normal. Sometimes it fails when driving but usually it's just when starting. I have replaced the throttle body, and tested the wires from the TPS, (throttle body position sensor) to the ECU and everything seem connected. I have cleaned all connectors at every point.
I found an ECU with the exact same part number and was assembled within two months of the one in my 2000VDP. The car it was removed from was a wrecked car so I'd assume it was in working order when it was wrecked.
When I installed the ECU in my car it shows the exact or similar warning codes and will not even try to start. Is there something that needs to be programmed with this ECU unit to operate in my car? Does my original ECU need reprogrammed? Does it have a bad part inside?
The DTC codes are: P1230~ Fuel Pump Low Speed Malfunction,
P1121 Throttle Position Sensor (TPS) Circuit Intermittent High Voltage, P0222 ~ Throttle/ Pedal position switch B circuit low; P0112 Intake Air Temperature Sensor 1 Circuit Low, P0102 ~ Mass Air Flow A Circuit Low. Sometimes there are other codes. On the display it reads, Failsafe Engine Mode, ASC not Available, TRAC not Available repeating through the same messages. Sometimes showing "GearBox Failure" as well. These messages I got with the replacement ECU. I get similar message with the original ECU but at least the car will finally get around to starting and running normally.

Does anyone know what goes wrong with these units? Like what internal component is the main cause of an ECU failure? Do they need reprogrammed at times in their life cycle? I have extensive experience troubleshooting to component level but I have no schematic or service information for the ECU.
Would appreciate any advice as I'm starting to doubt my sanity...

Thanks much, DN Warner

 

That long list could actually be an indication of a failing battery. Have one of the auto parts stores do a load test, and check the alternator, also.

Swapping the ECU usually requires reflash with factory level software. If you compare the VCATS of the two cars, you will see a 3 digit code at the end of the ECU part#, Like LJA1410 AC/020. That code has to match exactly, but even then a reflash may be required.

The failure mode for the ECU is often leaking diodes.

 

Hello RJ237, Thanks for the reply. I'm relatively sure the battery is OK..it's about 14 months old. The code numbers on the ECUs are exactly the same except the date is a few months newer. (Sept VS Dec.)
If the unit needs re-flashed, who does that besides the dealer? I suppose one would have to obtain the code and the interface and know the download instructions...which I certainly do not have. It would be interesting to see if that got the unit to work though...
Thanks for the leaking diode advice. I assume that must be in some power/ voltage circuit. Not sure if I'll fool with it unless I have a schematic.
Again, thanks much for you answers...Best, DN Warner

 

RJ...I think you meant to say leaking electrolytic capacitors, not diodes.

 

Not even a matching VCATS code will work with a ECM change. The ECM has to match the specific key.

 

What is the specific key and how is it programmed? is it linked to a specific VIN? If that was the case, how can anyone every buy a used ECM and have it work?
The mystery deepens...
Thanks much, Dave

 

Used = fit & reprogram keys. Few need to do it as the PCMs are very reliable. Mostly they don't fail and even then they can be fixed.