Chrysler 300M 2002 Service Manual page 2809

GENERAL INFORMATION
which prevents the use of the engine supplied TPS
signal, then 25 degrees of throttle angle will be
substituted.
Transmission Effects: Extremely erratic trans-
mission shifting with an intermittent TPS signal
just prior to setting the code. If the intermittent
does not last long enough to set the code, the
customer will say that the transmission violently
hunts between gears. The Transmission Control
System will use a calculated throttle angle sup-
plied by the PCM. The PCM will use a default
throttle angle of 25 degrees for the key start which
code was set. The PCM will try to use the TPS
signal again on the next key start. The MIL will
illuminate after 5 minutes of substituted operation
if the engine controller is not calibrated for throttle
substitution.
Possible causes:
> Open or shorted TPS signal and/or ground cir-
cuits
> PCM connector problems
> TPS or TPS connector (Check PCM DTC's)
> PCM
Name of code: P0870(31) - OD Hydraulic Pres-
sure Test Failure
P0845(32) - 2/4 Hydraulic Pressure Test Failure
P0992(33) - 2/4/OD 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 PCM 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 PCM 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 PCM verifies that the switch
closes when the corresponding 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 Limp-in mode.
Possible causes:
> Pressure switch sense circuit shorted to battery
between PCM and solenoid pack.
> Low line pressure
> Solenoid Pressure Switch assembly
Name of code: P0944(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 for a given gear are
open, a loss of prime test begins. All available
elements (in 1st gear LR, 2/4 and OD, in 2nd, 3rd,
and 4th gear 2/4 and OD) are turned on by the
PCM to see if pump prime exists. The code is set if
none of the pressure switches respond. The PCM
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 faults, which can be
caused by a lack of pump prime.
Transmission Effects: Vehicle will not move or
transmission slips. Normal operation will continue
if pump prime returns.
Possible causes:
> Low transmission fluid level
> PRNDL indicates a valid OD code in the hydrau-
lic reverse position
> Transmission fluid filter clogged or damaged.
> Transmission fluid filter improperly installed
(Bolts loose or O-ring missing)
> Oil pump - If a customer has a problem when the
transmission is cold. Where someone shifts to
reverse, reverse is engaged, and then shifts to
OD and does not get OD (gets a neutral condi-
tion), and then can not get reverse or OD for 3-20
seconds, replace the oil pump. High side clear-
ance in the oil pump will set a code 35. The pump
will prime upon start-up, but as the torque
converter purges air (drain down) the air will
leak across the inner rotor into the pump suction
port and cause a loss of prime right after the
shift into OD. After 3 - 20 seconds, pump prime
will return and normal operation will continue.
The pump should be replaced only after all other
possible causes above have been checked and
verified.
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