Vehicle: 2003 Jeep Grand Cherokee, 4WD, V8-4.7L, Automatic Transmission
Problem: The owner was concerned that the transmission had developed a harsh bang when shifting into gear and while shifting between gears on acceleration. In addition to the noise, the malfunction indicator light (MIL) was on.
Details: The technician connected a scan tool and retrieved the following diagnostic trouble codes (DTCs):
P0932 - Line Pressure Sensor Circuit Fault
P0935 - Line Pressure Sensor High
Not having a lot of experience with Jeep transmissions, the technician called ALLDATA Tech-Assist for some advice. The Tech-Assist consultant suggested to first check the reference voltage and ground supplies for the line pressure sensor and the signal return wire between the solenoid and the PCM.
If the line pressure sensor voltage, grounds and signal circuits tested good, the next step would be to measure the line pressure solenoid’s resistance. If the resistance test results were much higher or lower than 10 Ohms (or open), the solenoid was bad. (NOTE: Although the manufacturer did not supply that specification, 10 Ohms would be a typical reading.)
After the line pressure solenoid circuits tested good, the technician checked the solenoid’s resistance and found that it was open.
Confirmed Repair: He replaced the line pressure solenoid, cleared the DTCs and went for a test drive. The transmission shifted quietly and normally, the MIL remained off and DTCs did not return. Fixed!