Code 41, No Rpm Signal - Vehicle In Motion

Code 41 indicates ECM is on and reads no RPM signal from alternator. Code 41 could mean an open or ground in tachometer signal circuit, if engine is running with no RPM signal and vehicle is moving. If problem clears, Code 41 will store.

NOTE: The following step numbers refer to the numbers in the accompanying flow chart(s).

This step checks for voltage output at alternator "R" terminal which is source of RPM signal. Check for voltage increase as engine speed is increased.
This step indicates if RPM signal is being sent to ECM. Voltage reading should be approximately same as was noted in step 1). A voltage increase indicates signal is being generated by alternator and fault is bad connection at the ECM, or faulty ECM. To check connection at ECM, terminal must be removed from connector.
With an open circuit, there is still a small amount of voltage at ECM. It will not increase as throttle is opened.

Fig 1: Code 41, No RPM Signal-Vehicle In Motion

Fig 2: Code 41, No RPM Signal-Vehicle In Motion