A/T - High or Low Line Pressure
Date: 1996Technical Bulletin # 342
^ Transmission:
RE4 Series
^ Subject:
High or low line pressure
^ Application:
Nissan, Infiniti, Mazda, Subaru
RE4 Series
High or Low Line Pressure
Line pressure that is higher or lower than normal can be caused by an internal or external malfunction. An internal or external malfunction can be determined by measuring the voltage to the line pressure solenoid. The system that is used to control voltage to the line pressure solenoid of an RE4 series transmission is unique. There are two circuits used to control the voltage: one positive, one negative. The unique part is that both leads are connected to a single wire to the solenoid (figure 1).
The easiest way to check the voltage to the line pressure solenoid is to measure it at the dropping resistor (figures 2, 3, and 4).
NOTE:
Always confirm that there are no stored fault codes before performing any of the following electrical tests. If the computer offers a code for the line pressure solenoid, it can be checked at the dropping resistor. Normal resistance is 2.5-5.0 ohms.
Normal voltage to the line pressure solenoid is approximately .5-2.5v at an idle. As the throttle is opened, voltage will drop until it reaches its lowest value of approximately .2-.5v at full throttle (figure 5).
NOTE:
This voltage test can be done with the key on, engine off.
If voltage to the line pressure solenoid is correct, the problem is internal (line pressure solenoid, pilot valve, pressure modifier valve (some models), stuck slide, etc.).
If the voltage to the line pressure solenoid is not correct, check the voltage on the feed side of the dropping resistor (figure 4).
Voltage should be close to battery voltage at an idle and drop as the throttle is opened (figure 6).
NOTE:
This test can be done with the key on, engine off.
If the feed voltage is not correct check the resistance of the dropping resistor. Normal resistance is 11-i 3 ohms. If the resistor is out of specification, it will need to be replaced. The Nissan part number is 31037-31011. If the dropping resistor is within specifications, other model-specific electrical tests will need to be performed. Consult the factory repair manual for further testing.