Chrysler PT Cruiser 2001 Service Manual Supplement page 2754

GENERAL INFORMATION
at the solenoid pack pressure switches is checked.
There should be no voltage on the pressure switches
at this time. The TCM will then activate the relay.
Transmission Effects: The MIL illuminates and
the transmission system defaults to Relay Open
limp-in mode.
Possible causes:
> Short to battery on one or more pressure switch
sense circuits
> TCM connector problems
> Defective TCM
Name of code: P-1781(21) — OD Pressure Switch
Circuit
When monitored: Whenever the engine is run-
ning.
Set condition: This code is set if the OD pressure
switch is open or closed at the wrong time in a given
gear (see chart below).
Theory of operation: The Transmission system
uses three pressure switches to monitor the fluid
pressure in the L-R, 2-4, and OD clutch circuits.
The pressure switches are continuously monitored
for the correct states in each gear as shown below.
Normal Pressure Switch States
Gear L-R
R OP
N CL
1st CL
2nd OP
3rd OP
4th OP
OP = switch is open
CL = switch is closed
Transmission Effects: Normal operation will be
experienced if no other fault codes are present.
TCM will ignore the code. Limp-in condition will
only occur if code P-1781(21) is present with a code
P-0705(28).
Possible causes:
> If code P-1791(35) is present, ignore code
P-1781(21) and perform code P-1791 diagnostic
procedures
> OD pressure switch sense circuit open or shorted
to ground between TCM and solenoid pack
> OD pressure switch sense circuit shorted to bat-
tery
> Solenoid pack defectiv
> Loose valve body bolts
> Plugged filter - internal transmission or torque
converter failure
> TCM
2-4 OD
OP OP
OP OP
OP OP
CL OP
OP CL
CL CL
6
Name of code: P-1782(22) — 2-4 Pressure Switch
Circuit
When monitored: Whenever the engine is run-
ning.
Set condition: This code is set if the 2-4 pressure
switch is open or closed at the wrong time in a given
gear (see chart below).
Theory of operation: The Transmission system
uses three pressure switches to monitor the fluid
pressure in the L-R, 2-4, and OD elements. The
pressure switches are continuously monitored for
the correct states in each gear as shown below.
Normal Pressure Switch States
Gear L-R
R OP
N CL
1st CL
2nd OP
3rd OP
4th OP
OP = switch is open
CL = switch is closed
Transmission Effects: If the 2-4 pressure switch
is identified as closed in P or N, the code will
immediately be set and normal operation will be
allowed for that given key start. If the problem is
identified for 3 successive key starts, the transmis-
sion will go into relay open limp-in mode.
If the 2-4 pressure switch is identified as being
closed in 1st or 3rd gear and was not identified as
being closed in P or N, then 2nd gear or 4th gear
will be substituted for 1st or 3rd gear depending on
throttle angle and vehicle speed. A short period of
time after the gear substitution, the transmission
will return to normal operating mode. If the trans-
mission is shifted back into 1st or 3rd gear through
normal operation, and the 2-4 pressure switch re-
mains closed, 2nd or 4th gear will be substituted
briefly and then resume normal operation. If four
gear substitutions occur in a given key start, the
transmission will go into relay open limp-in mode.
If the 2-4 pressure switch is open (indicating no
2-4 clutch pressure) in 2nd or 4th gear, the TCM
sets code P-1782(22) and continues with normal
operation. The transmission will only go into relay
open limp-in mode if a code P-0705(28) is also
present. If no 2-4 clutch pressure is present a speed
ratio code P-0732(52) or P-0734(54) will be set and
cause the limp-in condition.
Possible causes:
> If code P-1791(35) is present, ignore code
P-1782(22) and perform code P-1791 diagnostic
procedures
> 2-4 pressure switch sense circuit open or shorted
to ground between TCM and solenoid pack
> 2-4 pressure switch sense circuit shorted to bat-
tery
2-4 OD
OP OP
OP OP
OP OP
CL OP
OP CL
CL CL