Hydraulic Pressure Test
Required Special Tools:
- MB992744: Vehicle communication interface-Lite (V.C.I.-Lite)
- MB992745: V.C.I.-Lite main harness A
- MB992747: V.C.I.-Lite USB cable short
- MB992748: V.C.I.-Lite USB cable long
- MB991958: Scan Tool (M.U.T.-III Sub Assembly)
- MB991824: Vehicles Communication Interface (V.C.I.)
- MB991827: M.U.T.-III USB Cable
- MB991910: M.U.T.-III Main Harness A (Vehicles with CAN communication system)
CAUTION:
This test must be performed with the transmission fluid temperature within the range of 70 to 80°C (158 to 176°F).
- Check the engine oil level, and add if necessary.
- Warm up the engine, and then perform test drive for approximately 10 minutes.
- Check the transmission fluid for leaks, level and contamination. Then top up or change if necessary.
- Operate the parking brake securely, and then chock the wheels.
- Connect the scan tool (M.U.T.-III), and then start the engine.WARNING: For safety, operators must not stand in front of and at the rear of the vehicle during this test.CAUTION: During this test, leave the brake pedal depressed fully.
- Use the scan tool (M.U.T.-III) (data list item number 20: Secondary pressure) to measure the secondary pressure (line pressure) by observing the conditions listed in the hydraulic pressure table.
- Stop the engine.
- If not within the standard value, take necessary steps according to the hydraulic pressure test diagnosis table.
HYDRAULIC PRESSURE SPECIFICATION (REFERENCE VALUE)
| TRANSMISSION RANGE | DURING ENGINE IDLING | DURING ENGINE STALL |
|---|---|---|
| "P", "N" | 0.50 MPa (72.5 psi) | - |
| "R", "D", "L" | 0.50 - 1.18 MPa (72.5 - 171.1 psi) | 4.04 - 4.54 MPa (585.9 - 658.4 psi) |
HYDRAULIC PRESSURE TEST DIAGNOSIS
| JUDGMENT RESULT | PROBABLE CASE | REMEDY | ||
|---|---|---|---|---|
| During engine idling | Low at all ranges ("P", "R", "N", "D", "L") | The hydraulic pressure delivery system or the oil pump may be faulty. | Worn oil pump | Replace the transaxle assembly |
| Damaged oil pump chain and sprocket | ||||
| Defective pressure regulator valve, or deteriorated spring | Replace the valve body assembly | |||
| Leaks in the hydraulic pressure circuit ranging from the oil strainer via the oil pump to the pressure regulator valve | Replace the transaxle assembly | |||
| The engine idling speed is low. | Check the engine system, and repair or replace if necessary. | |||
| Low at certain range(s) only. | Oil leaks may be present in the device or circuit relating to that range. | Replace the transaxle assembly | ||
| High | Sensor(s) or the pressure adjusting function may be faulty. | Malfunction of the accelerator pedal position sensor | Check the accelerator pedal position sensor, and repair or replace if necessary. | |
| Malfunction of the oil pressure sensor | Replace the valve body assembly | |||
| Malfunction of the line pressure solenoid valve (stuck off, open circuit or short circuit) | ||||
| Malfunction of the pressure regulator valve | ||||
| During engine stall | Oil pressure does not rise from that during the engine idling. | Sensor(s) or the pressure adjusting function may be faulty. | Malfunction of TCM | Check the TCM, and repair or replace if necessary. |
| Malfunction of the line pressure solenoid valve (stuck on or short circuit) | Replace the valve body assembly | |||
| Malfunction of the pressure regulator valve | ||||
| Oil pressure rises, but is not within the standard value. | The pressure supply system, sensor(s) or the pressure adjusting function may be faulty. | Worn oil pump | Replace the transaxle assembly | |
| Malfunction of the line pressure solenoid valve | Replace the valve body assembly | |||
| Malfunction of the pressure regulator valve | ||||
| Low at certain range(s) only. | Oil leaks may be present in the device or circuit relating to that range. | Replace the transaxle assembly | ||