3.4 Shift Solenoid Valve
3.4 Shift Solenoid Valve3.4.1 Description
The shift solenoid valve is used to control the oil flow used in gear selection, and torque converter clutch control. The solenoid is driven by the TCM at PWM rates from 0 to 100%
The diagnostic monitors the feed back voltage from the solenoid, the methods of fault detection dependent on the PWM duty cycle. Short circuits to Battery positive or ground, or open circuit can be detected.
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 IDTC 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 an open circuit test is performed. If this fails, (i.e. the solenoid is open circuit) then again, the appropriate IDTC 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 IDTC 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 IDTC 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.