Caprice V6-262 4.3L (1987)
Test Description: Step numbers refer to step numbers on diagnostic chart.
1.
Unless CKT 466 or the switch is open the "scan" tool should display no indicating not in 4th gear. The switch should be open only in 4th gear.
2.
Step 2 checks the wiring and ECM. with CKT 466 grounded the scan should display no (not in 4th gear).
3.
This verifies that the 4th gear switch is working. The "scan " should display yes in 4th gear.
4.
Disconnecting the TCC connector simulates an open switch to determine if CKT 446 is shorted to ground or the problem is in the transmission.
Diagnostic Aids: Road test the car and verify customer complaint. If the TCC is operating erratically on the "scan" check the 4th gear switch to be
sure it is not changing under steady throttle position. If it is changing states check the connections and wire routing carefully. If the 4th gear switch is
always open the TCC will engage as soon as there is sufficient oil pressure.
