The Transmission Control System may report any of the following DTC’s.
DTC P-Code Name of Code Limp-in MIL
78 P1652 Serial communication link malfunction No No
-2
79 P0562 Low battery voltage Yes Yes
94 P0613 Internal TCM Yes Yes
Notes:
P1xxx DTC’s will set the MIL only after 10 seconds of vehicle operation.
1 - The MIL will be lit only if DTC P0706 is also present
2 - The MIL will be lit by the engine controller
3 - The MIL will be lit only if the engine controller is not calibrated for throttle substitution.
Yes (underlined) indicates that this DTC can take up to five minutes of problem identification before
illuminating the MIL.
3.3.8 DTC DESCRIPTIONS
Name of code: P0613(11, 13, 45, 94) - Internal
TCM
When monitored: Whenever the key is in the Run
or Run/Start position.
Set condition: This code is set whenever Trans-
mission Control System senses an internal error.
Theory of operation: The PCM is constantly
monitoring its internal processor. If an internal
problem is detected, this DTC will be set. This DTC
can also be set by a bad ground to the PCM and/or
Trans Control Relay.
Transmission Effects: The MIL will illuminate
(this DTC can take up to five minutes of problem
identification before illuminating the MIL) and the
transmission system will default to the Immediate
Shutdown routine.
Possible causes:
> PCM ground circuit.
> Relay ground circuit
> PCM
Name of code: P1684(12) - Battery was Discon-
nected (Informational code Only)
When monitored: Whenever the key is in the
Run/Start position.
Set condition: This code is set whenever the PCM
is disconnected from battery power (B+) or ground.
It will also be set during the DRBIIIt Battery
Disconnect procedure.
Theory of operation: A battery backed RAM
(RandomAccess Memory) is used to maintain some
learned values. When the battery B(+) is discon-
nected, the memory is lost. When the B(+) is
restored, this memory loss is detected by the PCM.
The code is set and the learned values are initial-
ized to known constants or previously learned
values from EEPROM (Electronic Erasable Pro-
grammable Read Only Memory). This results in
the reinitialization of some parameters.
Transmission Effects: Loss of trouble code data.
Immediate Limp-in mode if power is lost while
operating the vehicle. Normal operation is re-
sumed if the power is restored during the same key
start.
Possible causes:
> Battery voltage removed from PCM
> PCM disconnected
> Dead Battery
> Low battery voltage during cranking
> Battery Disconnect by DRBIIIt or MDS2
> PCM ground circuit missing.
Name of code: P0891(14) - Transmission Relay
Always On
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 PCM senses
greater than 3 volts at the Trans Relay Output
(switched battery) terminal of the PCM prior to the
PCM 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
PCM. It is referred to as the Transmission Control
Relay Output circuit or switched battery.
Transmission Effects: The MIL will illuminate
and the transmission system defaults to Logical
Limp-in mode. Logical Limp-in mode results in the
same modes of operation as Limp-in. Since the
relay is stuck “on”, the PCM can not open the relay,
and the PCM shifts to 2nd gear.
Possible causes:
> Relay failure (welded contacts)
> Short to battery in 12-volt supply and/or
Transmission Control Relay Output circuit(s)
> Short to voltage
> PCM connector problems
> PCM
6
GENERAL INFORMATION
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