Chrysler PT Cruiser 2001 Service Manual Supplement page 2753

Transmission Effects: The MIL will illuminate
the transmission system defaults to Logical limp-in
mode. Logical Limp-in mode results in the same
modes of operation as Relay Open Limp-in. Since
the relay is stuck ''on'', the TCM can not open the
relay, and the TCM shifts to 2
Possible causes:
> Relay failure (welded contacts)
> Short to battery in 12-volt supply and/or trans-
mission control relay output circuit(s)
> Short to voltage
> TCM connector problems
> TCM
Name of code: P-1768(15) — Trans Control Relay
Circuit
When monitored: Continuously
Set condition: This code is set when less than 3
volts are present at the Trans Relay Output
(switched battery) terminals at the Transmission
Control Module (TCM) when the TCM is energizing
the relay.
Theory of operation: The transmission control
relay is used to supply power to the solenoid pack
when the transmission is in normal operating
mode. When the relay is off, no power is supplied to
the solenoid pack and the transmission is in ''limp-
in'' mode. The relay output is fed back to the TCM
through pins 16 and 17. It is referred to as the
Trans Relay Output circuit or ''switched battery''.
After a controller reset (ignition key turned to the
''run'' position or after cranking engine), the control-
ler energizes the relay. Prior to this the TCM
verifies that the contacts are open by checking for
no voltage at the switched battery terminals. After
the relay is energized, the TCM monitors the ter-
minals to verify that the voltage is greater than 3
volts.
Transmission Effects: The MIL illuminates and
the transmission system defaults to Relay Open
limp-in mode.
Possible causes:
> Relay failure (intermittent relay function caused
by oxidized or contaminated relay contacts)
> Short to ground or open circuit in the transmis-
sion control relay circuit(s)
> TCM connector problem
> TCM
Name of code: P-0725(18) — Engine Speed Sen-
sor Circuit
When monitored: Whenever the engine is run-
ning
Set condition: This code is set when the engine
speed sensed by the Transmission Control Module
(TCM) is less than 390 RPM or greater than 8000
RPM for more that 2.0 seconds.
nd
gear.
5
GENERAL INFORMATION
Theory of operation: The TCM uses a simulated
Crank Sensor signal to calculate engine RPM. This
signal is supplied by the PCM and uses a dedicated
circuit called the EATX RPM Signal circuit. If the
TCM interprets this signal to be out of range when
the engine is running (as reported by the PCM over
the bus) the code is set.
Transmission Effects: The MIL illuminates and
the transmissions system defaults to Relay Open
limp-in mode.
Possible causes:
> Open or short in EATX RPM Signal circuit.
> TCM and/or PCM connector problems
> TCM
> PCM
Name of code: P-0716(19) — Bus Communication
with Engine Module
When monitored: Continuously with key on.
Set condition: If no PCI bus messages are re-
ceived from the Powertrain Control Module (PCM)
for 10 seconds.
Theory of operation: The TCM communicates
with the PCM using the PCI bus. It relies on certain
information to function properly. The TCM contin-
uously monitors the PCI bus to check for messages
broadcast from the PCM.
Transmission Effects: Delayed 3-4 shifts. No
EMCC and early 3-4 shifts for a few minutes after
engine is started.
Possible causes:
> Open or shorted PCI bus circuit
> Bus bias problem
> TCM
> PCM
Name of code: P-1765(20) — Switched Battery
When monitored: Ignition key is turned from
''off '' position to ''run'' position and/or ignition key is
turned from ''crank'' position to ''run'' position.
Set condition: This code is set if the Transmission
Control Module (TCM) senses voltage on any of the
pressure switch inputs prior to the TCM energizing
the relay.
Theory of operation: The transmission control
relay is used to supply power to the solenoid pack
when the transmission is in normal operating
mode. When the relay is off, no power is supplied to
the solenoid pack and the transmission is in ''limp-
in'' mode. The relay output is fed back to the TCM
through pins 16 and 17. It is referred to as the
Trans Relay Output circuit or ''switched battery''.
Immediately after a controller reset (ignition key
turned to the ''run'' position or after cranking en-
gine), the TCM verifies that the relay contacts are
open by checking for no voltage at the switched
battery terminals. After this is verified, the voltage