The pump, yes. You would need pressure gauges and need to access the plug for testing the pump pressure. If you have no pressure, then it could be either one as the torque converter turns the front pump.
Line Pressure Check
* J-21867 - Pressure Gage
* J-21867-65 - Pressure Test Adapter (5.3 Only)
For equivalent regional tools, refer to Special Tools (See: Automatic Transmission/Transaxle > Electrical / Mechanical Repair).
* Before performing a line pressure check, verify that the pressure control (PC) solenoid valve is receiving the correct electrical signal from the PCM.
* Some conditions may be intermittent, therefore this test should be performed at least 3 times.
1. Install a scan tool.
Keep the brakes applied at all times in order to prevent unexpected vehicle motion. Personal injury may result if the vehicle moves unexpectedly.
2. Start the engine and set the parking brake.
3. Check for a stored Diagnostic Trouble Code (DTC).
4. Repair the vehicle, if necessary.
5. Check the fluid level. Refer to the Transmission Fluid Check (See: Fluid - A/T > Component Tests and General Diagnostics > Transmission Fluid Checking Procedure).
6. Check the manual linkage for proper adjustment.
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7. Turn the engine Off.
8. Loosen Exhaust cross-over pipe to allow attachment of J-21867-65 - Pressure Test Adapter (5.3 Only).
9. Remove the oil pressure test hole plug and install the J-21867 - Pressure Gage and the J-21867-65 - Adapter if used.
10. Put the gear selector in PARK range and set the parking brake.
11. Start the engine and allow the engine to warm up at idle.
Caution: The total test running time should not be longer than 2 minutes. Running the test longer than 2 minutes may damage the transaxle.
12. Access the PC solenoid valve control test on the scan tool.
13. Increase the PC solenoid actual current from 0 to 1 amps in 0.1 amp increments. Allow the pressure to stabilize for five seconds after each pressure change. Read the corresponding line pressure on the J-21867 - gage.
14. Refer to the Line Pressure (See: Automatic Transmission/Transaxle > Pressure, Vacuum and Temperature > Line Pressure) specification table. Compare the data to the table.
15. If pressure readings differ greatly from the table, refer to Incorrect Line Pressure (See: Automatic Transmission/Transaxle > Symptom Related Diagnostic Procedures > Incorrect Line Pressure).
16. Shut the engine OFF. Remove the J-21867 - gage and J-21867-65 - adapter if used.
17. Apply sealant GM P/N 12345382 (Canadian P/N 1095348) to the oil pressure test hole plug.
Caution: Refer to Fastener Caution (See: Vehicle > Vehicle Damage Warnings > Fastener Caution).
18. Install the oil pressure test hole plug and tighten to 12 Nm (106 lb in).
19. Re-tighten the exhaust cross-over pipe (5.3 only).
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Wednesday, March 17th, 2021 AT 3:57 PM