Chrysler PT Cruiser 2001 Service Manual Supplement page 2756

GENERAL INFORMATION
> Intermittent T1, T3, T41 or T42 circuits. Check
for corrosion, terminal push-outs or spread ter-
minals at 60-way and/or TRS switch 10-way
connector
> TRS
> TCM
> BCM
Scenario 3) - If the invalid code happened while
operating in the ''3'' or ''L'' position, then the ''3'' or
''L'' shift schedule and electronic display will be
frozen (regardless of whether ''OD'', ''3'' or ''L'' is
selected) until the shifter is moved to the ''N''
position (all PRNDL lights will illuminate) and
then back to the ''OD'' position and held there for at
least 3 seconds in order to resume the normal ''OD''
shift schedule and electronic display.
> Intermittent T1, T3, T41 or T42 circuits. Check
for corrosion, terminal push-outs or spread ter-
minals at 60-way and/or TRS, MVLPS, P/N, or
PRNDL switch 10-way connector
> TRS
> TCM
> BCM
These same symptoms may occur without the fault
code P-0705(28) getting set. It is possible that the
invalid code that was sensed by the TCM only
occurred once or twice during the given ignition key
start and/or did not last for longer than 0.1 second.
Name of code: P-0120(29) — Throttle Position
Signal
When monitored: Whenever the engine is run-
ning.
Set condition: This code is set if the throttle angle
goes out of range or if throttle angle changes
abruptly (ie: faster than the throttle body motion
could occur)
Theory of operation: The Transmission Control
Module (TCM) receives the throttle position signal
from the Throttle Position Sensor (TPS) through a
wire spliced into the TPS circuit to the PCM. The
TPS has a 5-volt pull up supplied from the Power-
train Control Module (PCM). The signal is checked
for out-of-range as well as intermittent (excessive
signal changes).
Transmission Effects: Extremely erratic trans-
mission shifting with an intermittent TPS signal
just prior to setting the code. If the intermittency
does not last long enough to set the code, the
customer will say that the transmission violently
hunts between gears. The TCM will use a ''calculat-
ed throttle angle'' supplied by the PCM over the PCI
bus. If the PCI bus is unavailable, the TCM will use
a default throttle angle of 24 degrees for the key
start in which the code was set. The TCM will try to
use the TPS signal again on the next key start.
Possible causes:
> Open or shorted TPS signal and/or ground cir-
cuits
> TCM connector problems
> TPS or TPS connector (Check PCM DTC's)
> PCM
> TCM
Name of code: P-1787(31) — OD Hydraulic Pres-
sure Test Failure
P-1788(32) — 2-4 Hydraulic Pressure Test Failure
P-1789(33) — OD/2-4 Hydraulic Pressure Test Fail-
ure
When monitored: In 1st, 2nd, or 3rd gear with
engine speed above 1000 RPM shortly after a shift
and every minute thereafter.
Set condition: Immediately after a shift into 1st,
2nd, or 3rd gear, with engine speed above 1000
RPM, the TCM momentarily turns on element
pressure to the 2-4 and/or OD clutch circuits to
identify that the appropriate pressure switch
closes. If the pressure switch does not close it is
tested again. If the switch does not close the second
time, the appropriate code is set.
Theory of operation: The Transmission Control
Module (TCM) tests the OD and 2-4 pressure
switches when they are off (OD and 2-4 are tested in
1st gear, OD in 2nd gear, and 2-4 in 3rd gear). The
test verifies that the switches are operational. The
TCM verifies that the switch closes when the cor-
responding element is applied. If a switch fails to
close, it is retested. If it fails the second test, the
code is set.
Transmission Effects: The MIL illuminates and
the transmission system defaults to Relay Open
limp-in mode.
Possible causes:
> Pressure switch sense circuit shorted to battery
between TCM and solenoid pack.
> Low line pressure
> Solenoid Pack
Name of code: P-1791(35) — Loss of Prime
When monitored: If the transmission is slipping
in any forward gear and the pressure switches are
not indicating pressure, a loss of prime test is run.
Set condition: If the transmission begins to slip in
any forward gear, and the pressure switch or
switches that should be closed a given gear are
open, a loss of prime test begins. All available
elements (in 1st gear L-4, 2-4 and OD, in 2nd, 3rd,
and 4th gear 2-4 and OD) are turned on by the
Transmission Control Module (TCM) to see if pump
prime exists. The code is set if none of the pressure
switches respond. The TCM will continue to run the
loss of prime test until pump pressure returns.
Theory of operation: The loss of prime test is
used to prevent transmission defaults which can be
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