3.7 Shift Interlock Solenoid
3.7 Shift Interlock Solenoid3.7.1 Description
The shift interlock solenoid is located at the front of the selector lever assembly. The selector lever is connected to a locking plate that has two holes that correspond to the Park (P) and Neutral (N) positions. When the ignition is on or the engine is running, the solenoid is energized by the TCM when the selector lever is in the Park or Neutral positions. When energized, the solenoid ejects a pin that engages in the locking plate preventing the lever from being moved.
When the footbrake is applied, a signal from a brake switch is passed to the TCM that de-energizes the solenoid allowing the lever to be moved from the Park or Neutral position. This prevents the selector from being moved to the Drive or Reverse position unintentionally and the application of the brakes prevents the vehicle 'creeping' when the gear is engaged.
Movement of the selector lever from the Park or Neutral positions is also prevented if the TCM senses that the engine speed is above 2500 rpm, even if the brake pedal is depressed.
The monitor operates in the same way as the shift solenoid monitor however the diagnostic tests are different.
The monitor starts by checking that the solenoid supply voltage is above its minimum threshold, the solenoid supply transistor is switched on and the low side solenoid drivers are unlocked. If any of these conditions are not met then the monitor will stop and restart. Once the entry conditions have been met then the monitor will take two successive captures of the duty cycle of the PWM driver signal to the solenoid.
If the two duty cycle ratios do not match the monitor will stop and be restarted. Providing the two duty cycle ratios match a check performed is to confirm the value is above 0%. If not a short circuit to ground test is performed on the solenoid. If this fails, (i.e. the solenoid is short circuit to ground) then the appropriate DTC is logged. If the solenoid is not open circuit to ground the monitor is stopped and restarted.
If the value of the duty cycle ratio is not 0% it is then checked against a low threshold of 7.6%. If the ratio is below this threshold, then a software diagnostic is run on the solenoid to check that the solenoid off voltage is between its lower and upper threshold. If this is the case then the appropriate is logged, if not the monitor is restarted. If the ratio of the duty cycle is above the low threshold, it is then checked against the high threshold of 92.4%. If the ratio is above the threshold, it checked for being stuck at 100%. If this is the case then open circuit t and short circuit to ground tests are performed. If this fails, (i.e. the solenoid is open circuit) then again, the appropriate DTC is logged.
If the ratio of the duty cycle is above 92.4% but below 100% then the solenoid on voltage is checked against its high threshold. If the voltage is above the high threshold then a short circuit to battery voltage has been detected and the appropriate DTC is logged.
The final check is performed if the duty cycle ratio is within the upper and lower limits. In this case, the solenoid on voltage is checked to ensure it is between its upper and lower voltage thresholds. If this is the case then the monitor is stopped and restarted. If not the DTC is logged.
If the above table does not include details of the following enabling conditions: - IAT, ECT, vehicle speed range, and time after engine start-up then the state of these parameters has no influence upon the execution of the monitor.