How to Test the Crank Sensor in a 1995 Caravan

The 1995 Dodge Caravan uses a high-energy ignition with a coil and distributor. The distributor houses an ignition pickup in the form of an optical switch. This serves the same purpose as a crankshaft sensor. It has an 8-volt optical switch pulsed through the use of a rotor with vertical metal blades spaced around it; for the width of each blade there is a corresponding open space or window.

Instructions

1

Test the sync signal for an out-of-range or no signal situation. The optical switch produces two distinct signals: It uses a sync signal for cranking or engine startup, and a reference signal when the engine is operating. Locate the wiring harness connector on the distributor. It is a round connector with four wires. The wires are numbered from the top left to right as 1 and 2, and the bottom wires are numbered from left to right as 3 and 4. The number 1 wire is the sync signal; the number 2 wire is the reference signal; the number 3 wire is the powertrain control module (PCM) 8-volt input; and the number 4 wire is the PCM negative.

2

Use the voltmeter and probe -- use the pointed end of the voltmeters probe to pierce the insulation of a wire so that the probe makes contact with the underlying wire -- the number 4 wire with the red lead. Place the black lead on a good ground. Turn the ignition key to the "On" position and the voltage should be below 0.10 volt, or a tenth of a volt. If the voltage is correct, go to the next step. If it is out of parameter, replace the pickup.

3

Move the red probe to the number 1 wire. The voltage should be 8.5 to 9.0 volts. If it is correct, move on to the next step. If it is not correct, the pickup is not getting the proper voltage. This is due to a faulty wire or PCM.

4

Turn the ignition key to the "Off" position. Unplug the connector on the distributor. Probe the sync wire, (number 1) on the harness side, not the distributor, with the red probe. Turn the key on. There should be 5 volts. If the voltage is good the pickup is bad. If the voltage is off, the wiring or the PCM is bad.