![]() If there's a low power code, use the DMM to check the solenoid's power feed. If the scanner described a high power circuit code, check the solenoid's ground side and follow the flow chart. A scanner identifies the faulty solenoid, or it's a related circuit. ![]() The diagnosis begins with a scanner and a DMM. The TCM activates them based upon inputs from both engine and transmission sensors. Solenoids are actuators, devices the transmission control unit activates to achieve the desired result mechanically. Most transmissions control the solenoid from the ground side by pulsing the ground circuit on and off.įor instance, if there were two solenoids, the transmission activates solenoid A for first gear, both solenoids for second gear, only solenoid B for third gear, and neither of the two for fourth. On some transmissions (usually older), the solenoid is powered by a 12 V signal from the (TCM) transmission control module. Shift solenoids can be controlled by either the ground or the power side of the circuit. ![]() A solenoid can be normally open or normally closed, depending on the transmission. When power is removed from the solenoid, the plunger is pushed by a spring to its normal position. They consist of a spring-loaded plunger wrapped with a coil of wire that, when energized, draws the plunger inwards, either opening or closing a hydraulic circuit. Standard on/off solenoids have only two positions, either on or off. Shift solenoids are actuators used by electronically controlled transmissions to control fluid flow.
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