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Home >> Chevrolet >> 2002 >> Blazer 4D Utility, 4WD, Part Time >> Repair and Diagnosis >> External Pages >> Different car >> Section 1327 (Automatic Transmission - Mu4 (Introduction, Service & Replacement)) >> Diagnostic Information and Procedures >> DTC P0770 >> Test Description

Test Description

WARNING: This page is about a different car, the 2004 Pontiac Vibe. 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. 1:  The Powertrain OBD System Check prompts the technician to complete some basic checks and store the freeze frame data on the scan tool if applicable. This creates an electronic copy of the data taken when the fault occurred. The information is then stored in the scan tool for later reference.
  2. 4:  This step checks for proper shift points.
  3. 5:  This step checks for a stuck closed lock-up solenoid.
  4. 6:  This step checks for a leaky lock-up solenoid.
  5. 7:  This step checks the condition of the valve body assembly.
  6. 8:  This step checks for a faulty PCM.
DTC P0770

Step Action Yes No
1  Was the On-Board Diagnostic (OBD) System Check performed? Go to Step 2  Go to Powertrain On Board Diagnostic (OBD) System Check - Automatic Transmission 
2 Does the scan tool display any other DTCs? Go to applicable DTC table Go to Step 3 
3
  1. Install a scan tool.
  2. Turn the ignition to ON, leaving the engine OFF.
  3. Perform the scan tool Clear DTC Information function.
  4. Operate the vehicle with the scan tool connected.
Did DTC P0770 reset?		 Go to Step 4  Go to Diagnostic Aids
4  Perform the Upshifts and Torque Converter Clutch Apply Procedure in Road Test Procedure  in order to diagnose the mechanical condition of the transaxle.
Was a mechanical failure detected?		 Go to Step 11  Go to Step 5 
5 
  1. Apply 12 V to the shift lock-up solenoid - positive to wire, negative to case.
  2. Apply 490 kPa (71 psi) of compressed air into shift solenoid inlet.
Did the lock-up solenoid outlet port open and did air escape?		 Go to Step 10  Go to Step 6 
6 
  1. Remove the lock-up solenoid.
  2. Apply 490 kPa (71 psi) of compressed air into the lock-up solenoid inlet port.
Did the lock-up solenoid outlet port stay closed and did no air leak?		 Go to Step 10  Go to Step 7 
7  Remove valve body and inspect its passages for any obstructions/restrictions. Refer to Solenoids and Wiring Harness Replacement .
Is the valve body in good condition?		 Go to Step 8  Go to Step 9 
8 
  1. Install a known good PCM. Refer to Powertrain Control Module (PCM) Replacement in Engine Controls.
  2. Perform the DTC Confirmation Procedure.
Does this DTC reset?		 Go to Step 11  Go to Step 12 
9 Repair or overhaul valve body assembly.
Is the action complete?		 Go to Step 13  -
10 Replace the lock-up solenoid.
Is the action complete?		 Go to Step 13  -
11 Refer to Road Test Procedure  for further diagnosis of the transaxle's performance. Repair as necessary.
Is the action complete?		 Go to Step 13  -
12 Replace Powertrain Control Module (PCM). Refer to Powertrain Control Module (PCM) Replacement in Engine Controls.
Is the action complete?		 Go to Step 13  -
13 Perform the DTC Confirmation Procedure.
Are any DTCs displayed on the Scan Tool?		 Go to applicable DTC table System OK
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