No Upshift To Overdrive
- Ensure engine and transmission is normal operating temperature. Retrieve trouble codes. See RETRIEVING CODES . Repair as needed. Clear codes. See CLEARING CODES .
- Perform manual shifting test. Reconnect TCM connector. Raise and support vehicle. Using DVOM, backprobe TCM harness connector. Start and operate vehicle. Place shift selector in "D" position. Operate vehicle through all gears. Monitor voltage at the TCM harness connector terminals S1 and S2. See Figure. Refer to the SHIFT SOLENOID VOLTAGE chart.
SHIFT SOLENOID VOLTAGE
| 1st Gear |
2nd Gear |
3rd Gear |
OD |
| No. 1 Shift Solenoid |
| 10-14 Volts |
10-14 Volts |
0 Volts |
0 Volts |
| No. 2 Shift Solenoid |
| 0 Volts |
10-14 Volts |
10-14 Volts |
0 Volts |
- If all voltages measured are within specification, inspect solenoids. See SHIFT SOLENOIDS under COMPONENT TESTING. If solenoids are okay, inspect and repair circuits between TCM and shift solenoids as needed. If circuits are okay, replace TCM and retest.
- If any voltage is not within specification, repeat operating vehicle through gears. Monitor voltage at TCM harness connector terminals "L" and 2. Voltage should be zero volts through all gears.
- If voltage is not within specification, replace Park/Neutral Position (PNP) switch and retest. If voltage is zero for both circuits, measure voltage between TCM harness connector OD terminal and ground.
- Voltage should be 5 volts with OD switch in OFF position, and zero volts in ON position. If voltage is not within specification, inspect OD switch and applicable circuits. See WIRING DIAGRAMS . Repair as needed.
- If voltage is within specification, measure voltage between TCM harness connector WT terminal and ground. See Figure. Voltage should be zero volts with engine coolant temperature below 77°F (25°C), and battery voltage with engine coolant temperature above 86°F (30°C).
- If voltage is not within specification, inspect CTS sensor. See ENGINE COOLANT TEMPERATURE SENSOR under COMPONENT TESTING. If ECT sensor is okay, refer to the appropriate SELF-DIAGNOSTICS article in ENGINE PERFORMANCE for further diagnostic information.
- If voltage is within specification, measure voltage between L4 terminal and ground. Voltage should be zero volts with transfer case in 4WD position, and battery voltage in 2WD position.
- If voltage is not within specification, replace 4WD switch (located on side of transfer case). If voltage is within specification, replace TCM and retest.