Diagnosis Fourth Gear

1. Turn on the ignition. Make sure 12 volts are present at the center terminal (dark blue wire) of the transmission connector. If not, check fuses, fusible links, A/C clutch relay, ignition switch, etc.

2. With 12 volts applied to the center wire of the transmission connector, connect a jumper wire from ground to the front terminal.

3. If fourth gear does not work, the solenoid may be bad or the problem is hydraulic or mechanical.

4. If fourth gear operates, the problem is electrical or computer related. See appropriate test under Computer Test.

COMPUTER TEST

TYPE I, turn on the ignition. Insure that the overdrive cancel switch is off. Check for five volts at the orange/white (pin 38). If no voltage is present, check the overdrive cancel module. See Component Tests. If five volts are present, check the operation of the TPS, coolant temperature sensor, vehicle speed sensor and park/neutral switch. See Component Tests.

Type II, turn on the ignition. Ensure that the overdrive cancel switch is off. Back-probe (tap into wire if necessary) orange/white wire (pin 44) at the 60-pin PCM connector. There should be zero volts. Turn on the overdrive cancel switch. Pin 44 should now have five volts (12 volts on some models). If the circuit does not work as described, check the overdrive cancel module. See Component Tests. If the circuit operates, but the overdrive solenoid does not work, check the operation of the TPS, coolant temperature sensor, vehicle speed sensor or park/neutral switch. See Component Tests.

Type III and 1992 Dakota, turn on the ignition. Ensure that the overdrive cancel switch is off. Back-probe the PCM terminals 55 and 37. There should be 12 volts present at both terminals. If there is no voltage at terminal 55, check the circuit between the PCM and the overdrive cancel switch or overdrive cancel module. See Component Tests.

Back-probe the PCM at terminal 10. Check for 12 volts with the overdrive cancel switch off and zero volts with the overdrive cancel switch on. If the voltage at terminal 10 does not work as described, check the overdrive cancel switch or overdrive cancel module.

If the voltage works as described, but the overdrive does not work, check the TPS, engine coolant temperature sensor, vehicle speed sensor and park/neutral switch. See Component Tests.