Chrysler PT Cruiser 2001 Service Manual Supplement page 2759

Possible causes:
> Sticky Throttle Position Sensor (TPS)
> Wiring or Connector problems in the Torque
Management Request Sense Circuit
> PCM
> TCM
Name of code: P-0736(50) — Speed Radio Error in
Reverse
P-0731(51) — Speed Ratio Error in 1st
P-0732(52) — Speed Ratio Error in 2nd
P-0733(53) — Speed Ratio Error in 3rd
P-0734(54) — Speed Ratio Error in 4th
P-0715(56) — Input Speed Sensor Error
P-0720(57) — Output Speed Sensor Error
P-1794(58) — Speed Sensor Ground Error
When monitored: The transmission gear/speed
ratio is monitored continuously while the transmis-
sion is in gear.
Set condition: This code is set if the gear/speed
ratio is not correct for a period of time.
– Codes 50 through 54 sets if the ratio of the
input RPM (Nt) to the output RPM (No) does
not match the given gear ratio.
– Code 56 sets if there is an excessive change in
input RPM in any gear
– Code 57 sets if there is an excessive change in
output RPM in any gear
– Code 58 sets after a TCM reset in neutral and
Nt/No equals a ratio of input to output 2.50
A hard code sets within 3 seconds, an intermittent
code sets within 15 seconds.
Theory of operation: The transmission system
uses two speed sensors, one to measure input RPM
and one to measure output RPM. These inputs are
essential for proper transmission operation. There-
fore, the integrity of this data is verified through
the following checks:
1. When in gear, if the gear/speed ratio does not
compare to a known gear ratio, the correspond-
ing in-gear trouble code is set (codes 50 through
54).
2. An excessive change in input or output speeds
indicating signal intermittency will result in
codes 56 and/or 57 being set.
3. After a TCM reset in neutral, observing erratic
output and input speed sensor signals indicates
a loss of the common speed sensors ground. This
sets a code 58.
Transmission Effects: The transmission will not
go into relay open limp-in mode until three gear/
speed ratio error events occur in a given key start.
This allows for intermittent problems to correct
themselves without opening the relay. However, if a
gear/speed ratio error develops, a code is always set,
but if the condition corrects itself the transmission
GENERAL INFORMATION
will continue without requiring the ignition key to
be cycled on and off. Many different events could
occur given the range of failures possible for codes
50 through 58. The following are a few examples:
– Codes 51, 52, 53, 54, 56, and 57 (at speeds
above 45 MPH) - The appropriate code is set,
EMCC is aborted and current gear is main-
tained. If while still traveling above 45, the
gear ratio becomes valid again, EMCC will
re-engage and normal operation will resume.
If the gear ratio becomes intermittent and
recovers three times in a give key start, the
current gear will be maintained and EMCC
inhibited, then the transmission will go into
relay open limp-in mode if throttle is applied
below 45 MPH or at 22 MPH with closed
throttle.
– Codes 51, 52, 53, 54, 56, and 57 (at speeds
between 22 and 45 MPH) - If one of these codes
is set between 22 and 45 MPH, the current
gear will be maintained until the gear/speed
ratio problem corrects itself. If throttle is ap-
plied, the trans will go to 2nd gear. If this
happens and the gear/speed ratio problem goes
away, normal operation will resume. If three
gear/speed ratio problems are identified in a
given key start, the current gear will be frozen
until throttle is applied. The transmission will
then go into relay open limp-in mode with
throttle applied at speeds between 22 and 45
MPH.
– Codes 51, 52, 53, 54, 56, and 57 (at speeds
below 22 MPH) - If a gear/speed ratio problem
is identified below 22 MPH, the transmission
will immediately substitute second gear for
the current gear. If the gear/speed ratio prob-
lem goes away, normal operation will resume.
If three gear/speed ratio problems are identi-
fied in a given key start, the transmission will
go into relay open limp-in mode.
Possible causes:
Code P-0736(50) - Excludes geartrain failures
which should be obvious upon disassembly.
> If code P-1791(35) is also set, follow diagnostic
procedure for code P-1791(35) first
> Valve body - #1 ball check or LR switch valve
sticking - may also set code P-0731(51)
> Speed sensor or associated wiring - may also set
codes P-0731(51), P-0715(56), or P-0720(57)
> Failed or slipping LR clutch - may also set code
P-0731(51)
– LR seal leakage (Intermittent no drive or re-
verse)
– Sticky LR accumulator seals (Intermittent no
drive or reverse)
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