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For 1990-2009 cars only

Circuit Description

Trim B solenoid is used to control oncoming, off-going, and holding pressure in any one of five clutches. This solenoid is referred to as a pressure proportional to current (PPC) solenoid since the output hydraulic pressure supplied by this solenoid is proportional to the controlled current command.

The transmission control module (TCM) uses information from the turbine and output speed sensors to detect if a clutch is slipping. The clutch being controlled by B solenoid will vary depending on the shift that was being completed.

DTC P0776 is a type A DTC.

Conditions for Running the DTC

    • The components are powered and ignition voltage is greater than 9.0 volts and less than 18 volts.
    • Turbine speed is greater than 60 RPM.
    • Output speed is greater than 125 RPM.
    • The transmission is at normal operating temperature.

Conditions for Setting the DTC

DTC P0776 sets when the TCM detects an incorrect oncoming ratio, during a forward range shift, for an accumulated number of occurrences.

Action Taken When the DTC Sets

    • The TCM illuminates the malfunction indicator lamp (MIL)
    • When failure occurs in a forward range, the transmission will go to the previous range. If failure occurs in NEUTRAL or REVERSE, the transmission will lock in NEUTRAL while diagnostic response is active.
    • If the shift selector is moved to NEUTRAL, the transmission will shift to NEUTRAL and in some cases, may lock in NEUTRAL.
    • If the shift selector is moved to REVERSE, the transmission will shift to REVERSE or NEUTRAL.
    • If the shift selector is returned to a forward range and the transmission is compromised by over speeding or direction change, the transmission will shift to NEUTRAL.
    • DTC P0776 will be stored in TCM history.
    • The TCM freezes shift adapts (DNA).
    • The TCM inhibits torque converter clutch (TCC) engagement.

Conditions for Clearing the DTC

A scan tool can clear the code from TCM history. The TCM automatically clears the DTC from TCM history if the vehicle completes 40 warm-up cycles without failure.

Diagnostic Aids

    • Inspect the wiring for poor electrical connections at the TCM. Inspect for the following conditions:
       - A bent terminal
       - A backed-out terminal
       - A damaged terminal
       - Poor terminal tension
       - A chafed wire
       - A broken wire inside the insulation
    • When diagnosing for an intermittent short or open, massage the wiring harness while watching the test equipment for a change.
    • You may have to drive the vehicle in order to experience a condition.
    • This DTC indicates the oncoming clutch, being controlled by B solenoid, is not applied or applied too slowly. This could indicate a leak or obstruction in a specific clutch apply circuit. Observe scan tool failure record data for previous or current range information when the DTC was set, to determine specific shift when the DTC was set. Refer to Solenoid and Clutch Chart to determine which clutch circuit is suspect.

       Important: Clutch failure due to installation of an engine power upgrade is not covered under the transmission manufacturers warranty.

    • Inspect for the presence of an add-on engine power package. When engine horsepower or torque is increased over factory rating, a shift flare condition may occur.

Test Description

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

  1. This step tests for proper ignition voltage.

  2. This step tests for erratic speed sensor readings.

  3. This step tests for internal hydraulic leakage.

  4. This step tests for clutch capacity.

Step

Action

Value

Yes

No

Schematic Reference: Automatic Transmission Controls Schematics

1

Did you perform the Diagnostic System Check - Automatic Transmission?

--

Go to Step 2

Go to Diagnostic System Check - Automatic Transmission

2

Measure the transmission fluid level. Refer to Transmission Fluid Check .

Is the transmission fluid level correct?

--

Go to Step 3

Go to Transmission Fluid Check

3

  1. Install the scan tool.
  2. Start the engine.
  3. Important: Before clearing the DTC, use the scan tool in order to record the Freeze Frame and Failure Records for reference. The Clear Info function will erase the data.

  4. Record the DTC Freeze Frame and Failure Records.
  5. Clear the DTC.
  6. Using the scan tool, measure ignition voltage.

Is the voltage within the specified range?

9-18 V

Go to Step 4

Go to DTC P0562 for low voltage or DTC P0563 for high voltage

4

  1. Start the engine.
  2. Drive the vehicle under normal operating conditions.
  3. Using the scan tool, monitor engine, turbine and output speed sensor readings.

Is speed sensor data erratic?

--

Go to the appropriate speed sensor DTC

Go to Step 5

5

  1. Connect a 2,000 kPa (300 psi) pressure gage to the line pressure tap. Refer to Line Pressure Check .
  2. Use the scan tool, in Clutch Test Mode, to cycle through all transmission ranges with the engine at idle and vehicle brakes applied. Record line pressure in each range.

Was the line pressure low in a specific range or in ranges where the same clutch was applied?

--

Go to Low Main Line Pressure in All Ranges

Go to Step 6

6

Notice: Refer to Transmission Stall Test Notice in the Preface section.

Conduct a clutch test for all forward ranges. Refer to Clutch Test .

Did turbine speed remain at zero in all ranges?

--

Go to Diagnostic Aids

Go to Step 7

7

  1. Remove the transmission oil pan. Refer to Automatic Transmission Fluid and Filter Replacement .
  2. Inspect for signs of clutch failure.

Are there signs of clutch failure?

--

Go to Step 8

Go to Step 9

8

Remove the transmission for overhaul or replacement. Refer to Transmission Replacement .

Did you complete the repair or replacement?

--

Go to Step 11

--

9

Inspect for a stuck or sticking B trim valve. Refer to Control Valve Body Cleaning and Inspection .

Did you find and correct a condition?

--

Go to Step 11

Go to Step 10

10

Replace B solenoid. Refer to Control Valve Solenoid Replacement .

Did you complete the replacement?

--

Go to Step 11

--

11

Perform the following procedure in order to verify the repair:

  1. Clear the DTC.
  2. Start the engine.
  3. Use the scan tool to reset adaptive values for all shifts.
  4. Operate the vehicle in all ranges under normal driving conditions.
  5. Select Specific DTC.
  6. Enter DTC P0776.

Has test run and passed?

--

System OK

Go to Step 1