1994 Toyota Camry Codes 12 and 41
First of all there are no signals from the distributer to the ECU that controls fuel delivery and Engine idle. The ECU does this based on all sensor inputs with the distributer being only one of the signals used..
Code 12 is RPM sent from the distributer to the ECU
Code 41 is the throttle position signal sent to the ECU
There are two different ECU, on is a California and one is other. The RPM signal and TPS signals are used differently in the Calif. ECU.
I suspect you might have a mix up of ECU. I am looking at the schematics now and that is the only thing different and if you have the wrong ECU it will cause those codes to be set.
Let me know
Suggested Repair
Verify that the installed ECM is the correct California or non-California unit for this Camry. A mismatched ECU uses the distributor RPM and throttle-position signals differently and can set codes 12 and 41. Confirm the correct ECU part rather than assuming the distributor directly controls fuel delivery and idle.
Conversation Summary
The owner of a 1994 Toyota Camry reported a persistent check-engine light, erratic idle, intermittent hard starting, and stalling at stops. Codes 12 and 41 remained after distributor, ignition, plug, wire, and throttle-position sensor work, and rebuilt ECUs did not correct it. A diagnostic shop found the other systems within specification and blamed the computer. The expert said the 2.2L uses code 12 for the distributor RPM signal and code 41 for the throttle-position signal, explained that the ECU controls fuel and idle from multiple inputs, and suspected a California versus non-California ECU mismatch.
