Diagnosis

* Automatic transmission malfunctions may be caused by five general causes: poor engine performance, incorrect adjustment, a fault in the hydraulic system, a mechanical fault, or a fault in the computer or its signal system.

* Always begin diagnosis of these problems by checking the following easily corrected items: check the automatic transmission fluid level and condition (see Subsection 2.7.5), and check the adjustment of the transmission linkage and throttle cable. Then road test the vehicle and check whether the problem has been corrected or whether further diagnosis is required.

* If the problem is not corrected after preliminary checks and adjustments, further transmission diagnosis should be left to specialists. See Subsection 1.5.36 for information on causes of transmission malfunctions.

Preliminary Checks

PROCEDURE
1. Drive the vehicle to bring the transmission to normal operating temperature.
2. Check the automatic transmission fluid level.
3. If the fluid level is low, add fluid to the specified level, then check the transmission for leaks (see below).
4. If the fluid level is high, drain off the excess, then check the drained fluid for engine coolant. Engine coolant in the automatic transmission fluid indicates that the internal radiator walls separating coolant and transmission fluid have leaked (see Subsection 2.3).
5. If the transmission fluid is foaming, drain the transmission completely and refill with new fluid, then check the old fluid for engine coolant and check whether the transmission fluid level rises in the transmission.
6. Check the engine idle speed.

* If the engine is faulty, do not perform preliminary checks until it has been repaired and is operating normally.

7. Check the throttle cable adjustment. Adjust it if necessary (see Subsection 7.2.4).

* Throttle cable adjustment may be correct when the engine is off and cold, but may not be correct when the engine is hot. Check the cable adjustment both when the engine is cold and when it has reached normal operating temperature.

8. Inspect the transmission shift cables. Make sure they are properly adjusted and move freely (refer to Subsection 7.2.5).

Leak Check

Most transmission fluid leaks are easy to detect visually. Repair usually consists of replacing a seal or gasket. If the leak is difficult to locate, proceed as follows.

PROCEDURE
1. Identify the leaking fluid. Make sure it is transmission fluid and not engine oil or brake fluid (automatic transmission fluid is red).
2. Try to locate the leak source. Drive the vehicle several kilometers, then park it over a large sheet of paper or cardboard. After one to two minutes, you should be able to see where the fluid is dripping onto the cardboard.
3. Carefully inspect the suspected leak points and the area around them. Pay particular attention to joints that use gaskets. Use a mirror to inspect hard-to-reach areas.
4. If you still cannot find the leak, thoroughly clean the suspected area with degreaser or solvent, then wipe it dry.
5. Drive the vehicle several kilometers at various speeds with the transmission at normal operating temperature. Then inspect the suspected area again.
6. Once the leak is located, determine its cause. If you replace a gasket but the mating surfaces are bent, the new gasket will not stop the leak. Bent flanges must be straightened.
7. Before repairing the leak, make sure the following possible causes have been eliminated, as they may cause the leak to return.

* Some of these causes can only be corrected with special equipment and appropriate experience. If you find such faults, consult a qualified specialist.

Gasket Leaks

Check the oil pan periodically. Make sure the bolts are securely tightened, none are missing, the gasket is in good condition, and the pan is not bent (dents in the pan may indicate damage to the valve body inside).
If the pan gasket leaks, the fluid level or fluid pressure may be too high, the vent may be blocked, the pan mounting bolts may be overtightened, the pan flanges may be bent, the transmission case mating surface may be damaged, the gasket may be damaged, or the transmission case may be cracked or porous. If sealant was used instead of a gasket between the transmission case and the pan, the wrong sealant may have been used.

Seal Leaks

If any transmission seal leaks, the fluid level or fluid pressure may be too high, the vent may be blocked, the seal bore may be damaged, the seal itself may be damaged or incorrectly installed, the shaft surface passing through the seal may be damaged or worn, or a worn and loose bearing may allow excessive free movement of the shaft. Make sure the seal on the transmission fluid level dipstick tube is properly installed. Periodically check the area around the speedometer drive or vehicle speed sensor for signs of leakage. If present, inspect the O-ring for damage.

Case Leaks

If the case itself leaks, the case walls are porous and it must be repaired or replaced.
Make sure the coolant hose connections are securely tightened and in good condition.
Fluid leaking from the vent tube or the fluid filler tube
This indicates that the transmission fluid level is too high, coolant is mixing with transmission fluid, the case walls are porous, the dipstick is incorrectly inserted, or the vent or drain passages are blocked.