Automatic Transmission Special Testing
Automatic Transmission Special TestingEngine Idle Speed Check
See SYMPTOM TROUBLESHOOTING CHART - ENGINE DRIVEABILITY for diagnosis and testing of the engine idle speed.
Line Pressure Test
Caution:
^ Carry out line pressure test prior to carrying out stall speed test. If line pressure is low at stall, do not carry out stall speed test or further transmission damage will occur. Do not maintain wide open throttle in any gear range for more than five seconds.
Note:
^ Certain sensor failures may cause high EPC, failure mode effect management (FMEM) actions. Be sure that self-test and electrical repairs have been carried out, or test results may be incorrect.
This test verifies line pressure is within specifications.
1. Connect pressure gauge to the line pressure tap on the transmission and a tachometer to the engine.
2. Start the engine, increase and maintain 1,000 engine rpm and check line pressures. See the line pressure chart to determine if line pressure within specifications.
Line Pressure Chart
3. If line pressure is not within specifications, check EPC pressure.
Electronic Pressure Control (EPC) (Part 1):
4. Connect Pressure Gauge to EPC pressure to EPC pressure tap.
5. Start the engine, increase and maintain 1,000 engine rpm and check EPC pressure. See the line pressure chart for specification.
6. If EPC pressure is not within specification, see ELECTRONIC PRESSURE CONTROL (EPC) SOLENOID 5R44E and 5R55E ONLY to diagnose EPC operation. P1746 If EPC operation is OK, see the line pressure diagnosis chart for line pressure concern causes.
Line Pressure Diagnosis Chart
Stall Speed Test
This test checks operation of the following items:
^ Torque converter clutch
^ Forward clutch
^ Low one-way clutch (OWC) assembly
^ Driveability concerns
Warning:
^ Apply the parking brake firmly while carrying out each stall test. Failure to follow these instructions may result in personal injury.
Caution:
^ Always carry out line pressure test procedures prior to carrying out the stall speed test. If line pressure is low at stall, do not carry out stall speed test or further transmission damage will occur.
Note:
^ The stall speed test should be carried out with the engine and transmission at normal operating temperatures.
1. Connect tachometer to the engine.
Caution:
^ After testing each of the following ranges D, 2, 1, and R, move the transmission range selector lever to N (NEUTRAL) and run engine at 1, 000 rpm for about 15 seconds to allow the torque converter to cool before testing the next range.
Caution:
^ Do not maintain wide open throttle in any range for more than five (5) seconds.
Caution:
^ If the engine rpm recorded by the tachometer exceeds maximum specified rpm, release the accelerator pedal immediately. Clutch or band slippage is indicated.
Note:
^ Prolonged use of this procedure may set diagnostic trouble code (DTC) P0712 or P1783. After carrying out stall speed test run OBD test and clear DTCs from memory.
2. Press accelerator pedal to floor (WOT) in each range. Record rpm reached in each range. Stall speeds should be as follows:
Stall Speed Chart
If stall speeds were too high, see the stall speed diagnosis chart. If stall speeds were too low, first check the engine idle speed. If engine idle is OK, remove torque converter and check the torque converter clutch for slippage.
Stall Speed Diagnosis Chart
Air Pressure Tests
A no-drive condition can exist even with correct transmission fluid pressure because of inoperative clutches or bands. An erratic shift can be located through a series of checks by substituting air pressure for fluid pressure to determine the location of the malfunction.
Follow the procedure to determine the location of the inoperative clutch or band by introducing air pressure into the various test plate passages.
Note:
^ Use only dry, regulated 276 kPa (40 psi) maximum air pressure.
Apply air to the appropriate passage(s). A dull thud should be felt or heard or movement could be observed when the component applies. There should be no hissing sound when the component is fully applied.
Note:
^ Cover the vent hole in the test plate with a clean, lint-free shop towel to prevent spray when the air is applied. Plugging the vent hole during testing will result in inaccurate results.
3. Drain transmission fluid and remove the transmission fluid pan.
4. Remove the main control valve body.
5. Install transmission test plate and gasket. Tighten bolts to 11 Nm (8 lb-ft).
6. Apply air to the appropriate clutch port (see the diagram). A dull thud may be heard or movement felt when the component is applied or released. If clutch seals or check balls are leaking a hissing sound may be heard.
7. Install the main control valve body after testing is completed and any repairs have been made.
If test results find that the servos do not operate, disassemble, clean and inspect them to locate the source of the concern.
If air pressure applied to the clutch passages fails to operate a clutch, or operates another clutch simultaneously, disassemble and use air pressure to check the fluid passages in the center support and clutches to detect obstructions.