Hi, I’m looking for some guidance on diagnosing a starting issue with my 1992 Lexus SC400.

I’ve been experiencing an intermittent no-start issue—some days the car starts up with no problem, and other days it just cranks but won’t start. Initially, I suspected a fuel pump issue, so I did a fuel pump bypass. However, the problem persisted. I can hear the fuel pump priming, so I know it’s functioning properly.

I also noticed that the car only starts when the Check Engine Light (CEL) illuminates during ignition. If the CEL doesn’t come on, the car won’t start. After trying various things, I decided to send the ECU to SIA Electronics for testing and repair. They found a few leaking capacitors and repaired them. Four weeks later, they sent the ECU back and claimed it tested fine.

However, after reinstalling the ECU, the car still won’t start—it just cranks. This time, I haven’t even had one successful start since installing the repaired ECU.

Can someone help guide me on how to properly diagnose this issue?


1992 Lexus sc400
135k miles

 

Hello,

Did the shop do anything other than simply replace the Capacitors? Electrolyte from the Capacitors, depending on the severity of the damage to said Capacitor, can also affect the PCB Traces and Neighboring Components, sometimes literally dissolving them, among other things. If the shop just replaced the capacitors and ran basic tests, chances are the ECU you got back is just as fried as it was, but now with some fresh Capacitors.

I would suggest contacting the shop for additional tests, if they claim it's working fine and the job was done right, they won't have any issues refunding you the repair costs if you send the ECU out to another company for a second opinion and they find that it's bad. While I haven't used any of their services, people around here claim that Tanin Auto is a good place for repairs like that.

Hope this helps and best of luck!

 

If the Check engine light doesn't come on, the ECU is bad. They didn't repair the correct thing and obviously didn't plug it into a car to make sure it works. We do both.

Our specific service for a no-start SC400 is here. Use the drop down menu to select your car and problem: https://taninautoelectronix.com/prod...00-ecu-repair/