the last couple times I have started my car and checked codes, I have my 02 codes that I know were there. Waiting on parts. But I’ve got U0402 the last couple times on startup, I don’t see the code if I clear it, doesn’t come back. Only happens on cold starts. The code is for invalid data received from transmission control module. It appears on both ecu 1 and 2 as the same code.
Possible wiring issue? Connector loose? Cold vs Hot, expanded metal when hot may be making the connection, when cold, connectors not making good connection?
Not sure any of that is valid, but that is what popped into my mind. The problem is the connector on the transmission is buried behind the driver side axle.
If it’s wiring it could be anywhere along the way up the back of the engine to the ECU’s.
Ed