DTC P0785 3-2 Shift Solenoid Circuit
Electrical 3.8L
The 3-2 shift solenoid
(SS) valve assembly is a normally-closed, 3-port, on/off device that controls
the 3-2 downshift. The solenoid attaches to the control valve body within the
transmission. The solenoid receives ignition voltage through circuit 239.
The powertrain control module (PCM) controls the
solenoid by providing a ground path on circuit 687. During a 3-2
downshift, the 2-4 band applies as the 3-4 clutch
releases. The PCM varies the timing between the 3-4 clutch release and the 2-4 band apply depending on the vehicle speed and the throttle
position.
When the PCM detects a
continuous open, short to ground or short to power in the 3-2 SS valve assembly
circuit, then DTC P0785 sets. DTC P0785 is a type B DTC.
Conditions
for Running the DTC
- The system voltage is
8-18 volts.
- The engine speed is greater than
450 RPM for 5 seconds.
- The engine is not in fuel cutoff.
Conditions
for Setting the DTC
DTC P0785 sets if
one of the following conditions occurs for 5 seconds:
Condition
1
The PCM commands the
solenoid ON and the voltage feedback remains high (B+).
Condition
2
The PCM commands the
solenoid OFF and the voltage feedback remains low (0 volts).
Action
Taken When the DTC Sets
- The PCM illuminates the malfunction
indicator lamp (MIL) during the second consecutive trip in which the
Conditions for Setting the DTC are met.
- The PCM commands a soft landing to
third gear.
- The PCM commands maximum line
pressure.
- The PCM inhibits TCC engagement.
- The PCM inhibits fourth gear if the
transmission is in hot mode.
- The PCM freezes shift adapts from
being updated.
- The PCM records the operating
conditions when the Conditions for Setting the DTC are met. The PCM stores
this information as Freeze Frame and Failure Records.
- The PCM stores DTC P0785 in the
PCM history during the second consecutive trip in which the Conditions for
Setting the DTC are met.
Conditions
for Clearing the MIL/DTC
- The PCM turns OFF the MIL during the
third consecutive trip in which the diagnostic test runs and passes.
- A scan tool can clear the MIL/DTC.
- The PCM clears the DTC from PCM
history if the vehicle completes 40 warm-up cycles without an
emission-related diagnostic fault occurring.
- The PCM cancels the DTC default
actions when the fault no longer exists and/or the ignition switch is OFF
long enough in order to power down the PCM.
- Inspect the connectors at the PCM,
the 3-2 SS valve and all other circuit connecting points for an
intermittent condition. Refer to Testing
for Intermittent and Poor Connections in Wiring Systems.
- Inspect the circuit wiring for an
intermittent condition. Refer to Testing
for Electrical Intermittents in Wiring
Systems.
The numbers below refer
to the step numbers on the diagnostic table.
|
DTC P0785 3-2 SS Circuit Electrical (3.8L) Step |
Action |
Value(s) |
Yes |
No |
|
Did
you perform the Powertrain Diagnostic System Check?
|
-- |
Go to A
Powertrain On Board Diagnostic (OBD) System Check
in Engine Controls |
||
Important: Before
clearing the DTC, use the Scan Tool in
order to record the Freeze Frame and Failure Records. Using the Clear Info
function erases the Freeze Frame and Failure Records from the PCM.
Are
any of the following DTCs also set?
|
-- |
|||
|
Inspect
the ENG C |
-- |
|||
|
Use
the Scan Tool
in order to command the 3-2 SS valve assembly ON and OFF three times,
while listening to the bottom of the transmission pan (a stethoscope may be
necessary). Does the solenoid click when commanded? |
-- |
Go to Diagnostic Aids |
||
Does
the test lamp illuminate? |
-- |
|||
Does
the test lamp turn ON and OFF with each command? |
-- |
|||
|
Is
the test lamp always ON? |
-- |
|||
Does
the resistance measure within the specified range? |
20-32 ohms |
|||
Do
both readings measure greater than the specified value? |
250 K ohms |
Go to Diagnostic Aids |
||
Does
the resistance measure within the specified range? |
20-32 ohms |
|||
Do
both readings measure greater than the specified value? |
250 K ohms |
|||
|
Important The condition that affects
this circuit may exist in other connecting branches of the circuit. Refer to Power
Distribution Schematics in Wiring Systems for complete circuit
distribution. Test
the power feed circuit (CKT 239) of the 3-2 SS valve assembly for a
short to ground between the engine wiring harness junction block 2 and
the AT inline 20-way connector. Refer to Circuit
Testing and Wiring
Repairs in Wiring Systems. Did you find and correct the condition? |
-- |
|||
|
Important The condition that affects
this circuit may exist in other connecting branches of the circuit. Refer to Power
Distribution Schematics in Wiring Systems for complete circuit
distribution. Test
the power feed circuit (CKT 839) of the 3-2 SS valve assembly for a
short to ground between the AT inline 20-way connector and the 3-2 SS
valve assembly. Refer to Circuit
Testing in Wiring Systems. Did you find a short to ground condition? |
-- |
|||
Did
you complete the replacement? |
-- |
-- |
||
|
Important The condition that affects
this circuit may exist in other connecting branches of the circuit. Refer to Power
Distribution Schematics in Wiring Systems for complete circuit
distribution. Test
the power feed circuit (CKT 239) of the 3-2 SS valve assembly for
an open. Refer to Circuit
Testing and Wiring
Repairs in Wiring Systems. Did you find and correct the condition? |
-- |
-- |
||
|
Test
the control circuit (CKT 687) of the 3-2 SS valve assembly for a
short to ground between the PCM connector C2 and the AT inline 20-way
connector. Refer to Circuit
Testing and Wiring
Repairs in Wiring Systems. Did you find and correct the condition? |
-- |
|||
|
Test
the control circuit (CKT 687) of the 3-2 SS valve assembly for an
open or short to power between the PCM connector C2 and the AT inline 20-way
connector. Refer to Circuit
Testing and Wiring
Repairs in Wiring Systems. Did you find and correct the condition? |
-- |
|||
|
Replace
the AT wiring harness assembly. Refer to Torque
Converter Clutch Pulse Width Modulation (TCC PWM) Solenoid, TCC Solenoid, and
Wiring Harness . Did you complete the replacement? |
-- |
-- |
||
|
Replace
the 3-2 SS valve assembly. Refer to Control
and Shift Solenoids Replacement . Did you complete the replacement? |
-- |
-- |
||
|
Replace
the PCM. Refer to PCM
Replacement/Programming in Engine Controls. Did you complete the
replacement? |
-- |
-- |
||
|
Perform
the following procedure in order to verify the repair:
Has
the test run and passed? |
-- |
System OK |