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Home >> Chevrolet >> 2002 >> Blazer 4D Utility, 4WD, Part Time >> Repair and Diagnosis >> External Pages >> Different car >> Section 1508 (Automatic Transmission, 4L60-E/4L65-E Diagnosis (DTC P0218 To DTC P2761)) >> Diagnosis >> DTC P0785 >> Test Description

Test Description

WARNING: This page is about a different car, the 2004 Chevrolet Corvette. However, it is still accessible from the selected car via links, so may be relevant.

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

  1. 4:  This step tests the ability of the PCM to control the solenoid.
  2. 5:  This step tests for power to the 3-2 SS valve assembly.
  3. 6:  This step tests the ability of the PCM and wiring to control the ground circuit.
  4. 8:  This step measures resistance of the automatic transmission (AT) 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
2
  1. Install a scan tool.
  2. Turn ON the ignition, with the engine OFF.
    3. 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.
  3. Record the DTC Freeze Frame and Failure Records.
  4. Clear the DTC.
Are any of the following DTCs also set?
  • P0740
  • P0753
  • P0758
  • P2761
 - Go to Step 3  Go to Step 4 
3 Inspect the ENG IGN 1 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 Go to Step 5 
5 
  1. Turn OFF the ignition.
  2. Disconnect the AT inline 20-way connector, additional DTCs may set.
  3. Install the J 44152  Jumper Harness (20 pins) on the engine side of the AT inline 20-way connector.
  4. Turn ON the ignition, with the engine OFF.
  5. Using the J 35616  GM Terminal Test Kit, connect a test lamp from terminal E of the J 44152  to ground.

    Refer to Automatic Transmission Inline 20-Way Connector End View .

Does the test lamp illuminate?		 - Go to Step 6  Go to Step 15 
6 
  1. Connect a test lamp between terminal E and terminal S of the J 44152  .

    Refer to Automatic Transmission Inline 20-Way Connector End View .

  2. Use the scan tool in order to command the 3-2 SS valve assembly ON and OFF three times.
Does the test lamp turn ON and OFF with each command?		 - Go to Step 8  Go to Step 7 
7 Is the test lamp always ON? - Go to Step 16  Go to Step 17 
8 
  1. Install the J 44152  on the transmission side of the AT inline 20-way connector.
  2. Using the DMM and the J 35616  , measure the resistance between the terminal E and terminal S of the J 44152  .

    Refer to Automatic Transmission Inline 20-Way Connector End View .

Does the resistance measure within the specified range?		 20-32 Ω Go to Step 9  Go to Step 10 
9
  1. Measure the resistance from terminal S to ground.
  2. Measure the resistance from terminal E to ground.
Do both readings measure greater than the specified value?		 250 K Ω Go to Intermittent Conditions in Engine Controls Go to Step 11 
10
  1. Disconnect the AT wiring harness assembly from the 3-2 SS valve assembly.
  2. Measure the resistance of the 3-2 SS valve assembly.
Does the resistance measure within the specified range?		 20-32 Ω Go to Step 18  Go to Step 19 
11
  1. Disconnect the AT wiring harness assembly from the 3-2 SS valve assembly.
  2. Measure the resistance from the component's terminals to ground.
Do both readings measure greater than the specified value?		 250 K Ω Go to Step 18  Go to Step 19 
12
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 ignition circuit of the 3-2 SS valve assembly for a short to ground between the underhood electrical center and the AT inline 20-way connector.Refer to Testing for Short to Ground and Wiring Repairs in Wiring Systems.Did you find and correct the condition?		 - Go to Step 21  Go to Step 13 
13
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 ignition circuit 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 Testing for Short to Ground in Wiring Systems.Did you find a short to ground condition?		 - Go to Step 18  Go to Step 14 
14
  1. Test each solenoid for a short to ground.
  2. Replace the faulty solenoid as necessary.
Did you complete the replacement?		 - Go to Step 21  -
15
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 ignition circuit of the 3-2 SS valve assembly for an open.Refer to Testing for Continuity and Wiring Repairs in Wiring Systems.Did you find and correct the condition?		 - Go to Step 21  -
16 Test the control circuit of the 3-2 SS valve assembly for a short to ground between the PCM connector C1 and the AT inline 20-way connector.
Refer to Testing for Short to Ground and Wiring Repairs in Wiring Systems.
Did you find and correct the condition?		 - Go to Step 21  Go to Step 20 
17 Test the control circuit of the 3-2 SS valve assembly for an open or short to power between the PCM connector C1 and the AT inline 20-way connector.
Refer to Testing for a Short to Voltage and Wiring Repairs in Wiring Systems.
Did you find and correct the condition?		 - Go to Step 21  Go to Step 20 
18 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?		 - Go to Step 21  -
19 Replace the 3-2 SS valve assembly.
Refer to Control and Shift Solenoids Replacement .
Did you complete the replacement?		 - Go to Step 21  -
20 Replace the PCM.
Refer to Powertrain Control Module (PCM) Replacement in Engine Controls.
Did you complete the replacement?		 - Go to Step 21  -
21 Perform the following procedure in order to verify the repair:
  1. Select DTC.
  2. Select Clear Info.
  3. Drive the vehicle in D3 or D4 and perform a 3-2 downshift. Ensure the following conditions are met:
    • The PCM commands the 3-2 SS valve assembly ON and the voltage feedback drops to zero.
    • The PCM commands the 3-2 SS valve assembly OFF and the voltage feedback increases to B+.
    • All conditions are met for 5 seconds.
  4. Select Specific DTC.
  5. Enter DTC P0785.

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 System OK
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