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Today’s electronic transmissions use control modules to control the transmission
pressure, shift timing, and quality. The module uses inputs from sensors like the
MAF or MAP, VSS, and ECT and then compares them to a shift schedule stored in
its memory. The module is either integrated in to the PCM or a standalone TCM.
The EPC or (electronic pressure control) is a PWM (pulse width modulated)
solenoid. It typically replaces the throttle valve or vacuum modulator in hydraulic
operated transmissions. The TCM uses this solenoid to control mainline pressure
through out the transmission.
The EPC contains a spool valve and a spring. It’s a variable force solenoid that
changes at a rate of around 32 Hz (32 times per second). This gives the electronic
solenoid more precise control than the conventional hydraulic pressure control
system.
The solenoid uses spring pressure to keep the solenoid closed providing
maximum system pressure. As the module increases current to the solenoids
windings the EPC plunger/spool valve is moved opening the exhaust port and
reducing system pressure.
If the vehicles line pressure is below specifications the EPC solenoid needs to be
tested. Connect a pressure gauge to the transmissions EPC port and then start the
engine. Then check the reading against manufacturer specifications. If the pressure
is within specifications there may be an internal leak downstream to the EPC.
pressure, shift timing, and quality. The module uses inputs from sensors like the
MAF or MAP, VSS, and ECT and then compares them to a shift schedule stored in
its memory. The module is either integrated in to the PCM or a standalone TCM.
The EPC or (electronic pressure control) is a PWM (pulse width modulated)
solenoid. It typically replaces the throttle valve or vacuum modulator in hydraulic
operated transmissions. The TCM uses this solenoid to control mainline pressure
through out the transmission.
The EPC contains a spool valve and a spring. It’s a variable force solenoid that
changes at a rate of around 32 Hz (32 times per second). This gives the electronic
solenoid more precise control than the conventional hydraulic pressure control
system.
The solenoid uses spring pressure to keep the solenoid closed providing
maximum system pressure. As the module increases current to the solenoids
windings the EPC plunger/spool valve is moved opening the exhaust port and
reducing system pressure.
If the vehicles line pressure is below specifications the EPC solenoid needs to be
tested. Connect a pressure gauge to the transmissions EPC port and then start the
engine. Then check the reading against manufacturer specifications. If the pressure
is within specifications there may be an internal leak downstream to the EPC.