Circuit Description
During normal driving modes the powertrain control module (PCM) adapts line
pressure to prevent clutch slip and harsh shifts. This is accomplished by modulating
the line pressure actuator ground (1530) to raise or lower pressure. Open circuit
= high pressure, grounded circuit = low pressure. If there is too much slip in all
gears and line pressure has been commanded high, it is determined that actual line
pressure is too low.
Conditions for Setting the DTC
DTC P0745 is set when the PCM has detected the following conditions within
the same ignition cycle:
| • | The transaxle diagnostic trouble codes DTC P0731, P0732, P0733
and P0734 are detected. |
| • | Since these diagnostic trouble DTCs are set, no forward gears are available. |
Repair Verification
Monitor the DTC menu ode Status for Pass Since Code Clear and Pass This Ignition
Cycle. When both have passed, the repair is verified.
Criteria for pass:
| • | Steady state in 2nd, 3rd, and 4th with no slip for 0.4 seconds. |
| • | The engine torque is greater than 30 counts with no slip for 1.0 seconds. |
Diagnostic Aids
| • | Could be a hot or cold only condition. If condition is intermittent, try
to reproduce conditions in malfunction (MALF) table to reset DTC. |
| • | When the PCM detects a fault in the circuit, (open, ground short), the
PCM will open the circuit internally to protect the circuit. |
Test Description
The numbers below refer to the step numbers on the diagnostic table.
-
Check for DTC P0746. It must be eliminated
first as a possible cause of a DTC P0745.
-
Check actuator operation. Use actuator quick check
in test section located at the end of the code charts. The actuator quick test will
pulse width modulate (PWM) the actuators at a set rate. Listen and compare noise of
the line pressure actuator to that of other actuators. The noise of all should be
similar.
| | Important: To check actuator operation, command actuator
quick test using the scan tool.
|
| • | If noise is faint or not present, replace the line pressure actuator. Be sure
to check all connections at the actuator and connector plate before replacing the
actuator. |
| • | If noise is audible, same as other actuators, the pressure regulator valve
may be binding in the bore or there is pump damage. |
-
Check the pressure regulator valve operation. Use
pressure test in the test section at the end of the DTC charts. Make sure the pressure
increases in correct increments during the pressure test.
-
If no gears are available, a DTC P0730 will
probably be set. Make sure the pressure increases in correct increments during pressure
test. If pressure changes erratically and moves in large increments, the pressure
regulator valve is probably sticking in the bore.
-
Check for the following conditions:
| • | Pressure regulator valve stuck |
| • | Sump suction filter restricted |
| • | Internal leak, casting or pump to case seal leak |
