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Home >> Chevy Truck >> 2011 >> Tahoe 4WD V8-5.3L >> Repair and Diagnosis >> Transmission and Drivetrain >> Automatic Transmission/Transaxle >> Testing and Inspection >> Component Tests and General Diagnostics >> 2ML70 - Automatic Transmission >> Line Pressure Check

Line Pressure Check




Line Pressure Check

Special Tools
* J 21867 - Pressure Gauge
* J 45056 - Transmission Oil Pressure Gauge Adapter

For equivalent regional tools refer to Special Tools 2ML70 - Automatic Transmission.

Main Fluid Pump






Warning

Keep the brakes applied at all times in order to prevent unexpected vehicle motion. Personal injury may result if the vehicle moves unexpectedly.

1. Install a scan tool.
2. Start the engine.
3. Inspect the transmission for the proper fluid level. Refer to Transmission Fluid Level and Condition Check Transmission Fluid Level and Condition Check.
4. Use the scan tool to inspect for any active or stored diagnostic trouble codes. If there are any DTC's, refer to that DTC table first.
5. Inspect the manual linkage at the transmission for proper function.
6. Turn the engine OFF.

Warning

When the transmission is at operating temperatures, take necessary precautions when removing the auxiliary pump pressure test hole plug, to avoid being burned by the catalytic converter.

Note: You may need to remove or disconnect components in order to gain access to the transmission line pressure test hole plug.

7. Remove the line pressure test hole plug.
8. Install J 45056 - oil pressure gauge adapter fitting prior to connecting the oil pressure gauge.
9. Install the J 21867 - pressure gauge.
10. Access the Scan Tool Transmission Output Controls for the Line PC Solenoid.
11. Start the engine.

Note: In order to achieve accurate line pressure readings, the following procedure must be performed at least 3 times in order to gather uniform pressure readings. Also if you do not have the hood open the engine may go in to AutoStop.

The scan tool is only able to control the line PC solenoid in PARK and NEUTRAL with engine speeds below 1500 RPM. This protects the clutches from extreme high or low line pressures.

12. Use the scan tool to increase and decrease the Line PC Solenoid in increments of approximately 100 KPa (15 psi). The scan tool commands the increment values automatically.
13. Allow the pressure to stabilize between increments.
14. Compare your pressure readings on the scan tool to those indicated on the J 21867 - pressure gauge.
15. If the pressure readings vary greatly, refer to Main Fluid Pump Pressure High or Low Main Fluid Pump Pressure High or Low.
16. Turn the engine OFF.
17. Disconnect the J 21867 - pressure gauge and remove the J 45056 - oil pressure gauge adapter fitting.

Caution: Refer to Fastener Caution Fastener Caution.

18. Install the line pressure test hole plug. Tighten the pressure plug to 11 Nm (97 lb in).

Auxiliary Fluid Pump






Warning

Keep the brakes applied at all times in order to prevent unexpected vehicle motion. Personal injury may result if the vehicle moves unexpectedly.

1. Install a scan tool.
2. Start the engine.
3. Inspect the transmission for the proper fluid level. Refer to Transmission Fluid Level and Condition Check Transmission Fluid Level and Condition Check.
4. Use the scan tool to inspect for any active or stored diagnostic trouble codes. If there are any DTC's refer to that DTC table.
5. Inspect the manual linkage at the transmission for proper function.
6. Turn the engine OFF, connect Midtronic 165-PSC charger.

Warning

When the transmission is at operating temperatures, take necessary precautions when removing the auxiliary pump pressure test hole plug, to avoid being burned by the catalytic converter.

Note: You may need to remove or disconnect components in order to gain access to the transmission auxiliary pump pressure test hole plug.

7. Remove the auxiliary pump pressure test hole plug.
8. Install J 45056 - oil pressure gauge adapter fitting prior to connecting the oil pressure gauge.
9. Install the J 21867 - pressure gauge.
10. Access the Scan Tool Hybrid Output Controls for the Aux Trans Pump Speed.
11. Turn key to the Run Position but do not start the engine.

Note: In order to achieve accurate aux pump pressure readings, the following procedure must be performed at least 3 times in order to gather uniform pressure readings.

12. Use the scan tool to increase and decrease the Aux Pump Speed in increments of approximately 25%. The scan tool commands the increment values automatically starting with 25% going up to 75% and returning down to 25%. The pump should be allowed to run for 60 seconds at each commanded speed.
13. Allow the pressure to stabilize between increments.
14. Your pressure readings on the J 21867 - pressure gauge should slightly increase with each speed command. The J 21867 - pressure
gauge at 25% should be approximately 40-70 PSI and end up at 75% being approximately 90-120 PSI.
15. If the pressure readings vary greatly, refer to Auxiliary Fluid Pump Pressure High or Low Auxiliary Fluid Pump Pressure High or Low.
16. Turn the key OFF.
17. Disconnect the J 21867 - pressure gauge and remove the J 45056 - oil pressure gauge adapter fitting.

Caution: Refer to Fastener Caution Fastener Caution.

18. Install the auxiliary pump pressure test hole plug. Tighten the pressure plug to 11 Nm (97 lb in).

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