Hummer H2. Manual — part 2493

DTC P0785

21

zero.

z

The PCM commands the 2-3 SS valve
OFF and the voltage feedback increases
to B+.

z

All conditions are met for 5 seconds.

4. Select Specific DTC.

5. Enter DTC P0758.

Has the test run and passed?

-

Go to Step 22

Go to Step 2

22

With the scan tool, observe the stored information,
capture info, and DTC Info.
Does the scan tool display any DTCs that you have
not diagnosed?

-

Go to Diagnostic

Trouble Code

(DTC) List in

Engine Controls -

6.0L (LQ4)

System OK

2004 Hummer H2

2004 TRANSMISSION Automatic Transmission - 4L60-E/4L65-E Diagnosis (DTC P0218 To DTC P2771) - Hummer H2

Fig. 20: 3-2 Shift Solenoid (SS) Valve Assembly Diagram
Courtesy of GENERAL MOTORS CORP.

Circuit Description

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 the Ignition 0 voltage circuit. The powertrain control module (PCM) controls the
solenoid by providing a ground path on the 3-2 shift solenoid valve control circuit. 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

2004 Hummer H2

2004 TRANSMISSION Automatic Transmission - 4L60-E/4L65-E Diagnosis (DTC P0218 To DTC P2771) - Hummer H2

z

The engine speed is greater than 450 RPM for 5 seconds.

z

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

z

The PCM illuminates the malfunction indicator lamp (MIL) during the second consecutive trip in which
the Conditions for Setting the DTC are met.

z

The PCM commands a soft landing to third gear.

z

The PCM commands maximum line pressure.

z

The PCM inhibits TCC engagement.

z

The PCM inhibits 4th gear if the transmission is in hot mode.

z

The PCM freezes transmission adapt functions.

z

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.

z

The PCM stores DTC P0785 in PCM history during the second consecutive trip in which the Conditions
for Setting the DTC are met.

Conditions for Clearing the MIL/DTC

z

The PCM turns OFF the MIL during the third consecutive trip in which the diagnostic test runs and
passes.

z

A scan tool can clear the MIL/DTC.

z

The PCM clears the DTC from PCM history if the vehicle completes 40 warm-up cycles without an
emission-related diagnostic fault occurring.

z

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.

Test Description

The item numbers below refer to the step numbers on the diagnostic table.

4: This step tests the ability of the PCM to control the solenoid.

2004 Hummer H2

2004 TRANSMISSION Automatic Transmission - 4L60-E/4L65-E Diagnosis (DTC P0218 To DTC P2771) - Hummer H2

5: This step tests for voltage to the solenoid.

6: This step tests the ability of the PCM and the wiring to control the ground circuit.

8: This step measures the resistance of the automatic transmission wiring harness assembly and the 3-2
SS valve assembly.

DTC P0785

Step

Action

Value

(s)

Yes

No

1

Did you perform the Diagnostic System Check -
Engine Controls?

-

Go to Step 2

Go to Diagnostic

System Check -

Engine Controls

in Engine

Controls - 6.0L

(LQ4)

2

1. Install a scan tool.

2. Turn ON the ignition, with the engine OFF.

3. Record the DTC Freeze Frame and Failure

Records.

4. Clear the DTC.

Are any of the following DTCs also set?

z

P0740

z

P0753

z

P0758

z

P2761

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.

-

Go to Step 3

Go to Step 4

3

Inspect the IGN 0 fuse for an open.
Refer to Circuit Protection - Fuses in Wiring
Systems.
Is the fuse open?

-

Go to Step 12

Go to Step 5

4

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

Intermittent

Conditions in

Engine Controls -

6.0L (LQ4)

Go to Step 5

2004 Hummer H2

2004 TRANSMISSION Automatic Transmission - 4L60-E/4L65-E Diagnosis (DTC P0218 To DTC P2771) - Hummer H2