Code 72, Gear Selector Switch, "Y" Body
ECM monitors 2nd, 3rd and 4th gear switch status. ECM uses this information to help determine shift points as well as determining TCC apply times. If ECM notes a 3rd gear switch signal without detecting a 2nd gear switch signal, Code 72 will set. An open in 2nd gear switch status circuit will cause this code to set.
NOTE:
Test numbers refer to numbers on diagnostic chart.
- Code 72 will set if 2nd gear switch is open, vehicle speed is greater than 30 MPH, TPS is greater than 70 percent, engine speed is greater than 5000 RPM and all conditions have been met for 1 1/2 seconds.
- This step checks operation of 2nd gear switch. When transmission shifts into 2nd gear, "Scan" tester should indicate 2nd gear on.
- Disconnecting TCC connector simulates an open switch to determine if 2nd gear switch circuit is shorted to ground or if a problem exists inside of transmission.
- This step determines if ECM and wiring are okay. Grounding 2nd gear switch circuit should cause "Scan" tester 2nd gear status to display "yes", indicating transmission is in 2nd gear.