Dtc P1850 Brake Band Apply Solenoid Malfunction - Isuzu Trooper 1999 Workshop Manual

7A1–78 TRANSMISSION CONTROL SYSTEM (4L30–E)

DTC P1850 Brake Band Apply Solenoid Malfunction

Circuit Description
f The brake band apply solenoid is a normally open
solenoid which controls the flow of fluid for brake band
application. The Powertrain Control Module (PCM)
uses Pulse Width Modulation (PWM) and changes
the duty cycle to control the solenoid. The PCM turns
the solenoid on (energized) and off (deenergized) at a
constant frequency. The length of time the solenoid is
energized during each on/off cycle is called the pulse
width. By varying or "modulating" the pulse width, the
solenoid output pressure is changed.
solenoid is normally open, increasing the pulse width
increases the duty cycle and decreases the output
pressure. PWM control provides smooth band
application without an accumulator. The band is only
applied in first and second gears.
f In the event of an electrical failure (open), the
solenoid regulates at the maximum oil flow (0% duty
cycle).
f The solenoid is activated by current. This current is
produced by applying a voltage to one side (the High
side) and a ground to the other side (Low side).
f The High Side Driver (HSD) is a circuit of the PCM
that acts as a switch between the solenoids and the
supply voltage. The High side of the solenoid is
permanently supplied with voltage. When the ignition
is off, the HSD is turned off.
This DTC detects a continuous open or short to ground in
the brake band apply solenoid circuit or the brake band
apply solenoid. This is a type "D" DTC.
Conditions For Setting The DTC
f Battery voltage is between 10 and 16 volts.
f Ignition is "on", Engine "run".
f The PCM commands the solenoid "on" and the
voltage remains high (B+) or the PCM commands the
solenoid "off" and the voltage remains low (zero
Since the
volts).
f All conditions met in 1.3 seconds.
Action Taken When The DTC Sets
f Inhibit brake band apply solenoid.
f The PCM will not illuminate the Malfunction Indicator
Lamp (MIL).
Conditions For Clearing The DTC
f The DTC can be cleared from the PCM history by
using a scan tool.
f The DTC will be cleared from history when the vehicle
has achieved 40 warmup cycles without a failure
reported.
f The PCM will cancel the DTC default actions when
the fault no longer exists and the ignition is cycled "off"
long enough to power down the PCM.
D07RW009