Component Tests

Throttle Position Sensor:
Back-probe the TPS signal return wire at the PCM pin 22 (orange/dark blue wire). There should be .5-1.5 volts at closed throttle and 3.4-4.2 volts at W.O.T. If not, check the related circuits or replace TPS.

Coolant temperature Sensor:
Disconnect the sensor. Measure the resistance across the sensor terminals. At 70°F, resistance should be 7,000-13,000 ohms. At 200°F, resistance should be 700-1,000 ohms. If not, replace the sensor.

Oil Temperature Switch:
Switch should be open below 270°F and closed above 270°F.

Overdrive Switch:
All switches work by momentarily making contact to ground with the signal wire coming from the overdrive cancel module or PCM. See diagrams under Operation for typical switch circuits.

VSS:
Back-probe PCM pin 48 on TYPE I (or PCM pin 47 on all others). Turn on the ignition and raise the drive wheels. The voltmeter should pulse as the wheels are turned.

Overdrive Cancel Module:

On TYPE I, disconnect the overdrive cancel module. Check for battery voltage at the overdrive control module pin five (to PCM), pin six (from the overdrive solenoid) and pin seven (from the ignition fuse). If no voltage is present, check these circuits. Ensure pin four has continuity to ground. On modules with a transmission oil temperature sensor, make sure the circuit between pin seven and the sensor is not shorted to ground. If no problems are found, replace the overdrive control module.

On TYPE II, ensure that battery voltage is present at the overdrive control module pin four (from ignition fuse). If not, repair the ignition feed circuit. Make sure pin two (black wire) has continuity to ground. Back-probe pin three (orange/white wire). Turn off the overdrive cancel switch. There should be zero volts. Turn on the overdrive cancel switch. There should be 12 volts present. If the module does not work as described, test the overdrive cancel switch. See Component Tests. On models with a transmission temperature switch, make sure the circuit between pin four and the sensor is not shorted to ground. If no problems are found, replace overdrive control module.

On TYPE III, disconnect the overdrive switch. Continuity should be present between pins three and one when the button is pushed. Apply 12 volts to pin six, and ground pin one. The overdrive cancel bulb should be on. Apply 12 volts to pin four and ground pin one. The overdrive-cancel illumination bulb on the dash should come on.

On 1992 Dakota, disconnect the overdrive cancel module. Ensure that the 12 volts are present at pins six and two. Ensure that the 12 volts are present at pin three. Make sure no continuity is present when oil temperature is less than 270°F, and continuity is present when oil temperature is more than 270°F, and continuity is present when oil temperature is more than 270°F. Turn off the ignition. Make sure voltage switches from high to low as the overdrive cancel switch is pushed. If the overdrive cancel module does not work as described, replace it.