Mopar Electronic Speed Control System Test Procedure (K, E, G, L, M Bodies, Light Truck, Van & T115)

This procedure requires the use of a volt-ohm meter capable of reading D.C. voltages of up to 15 volts and resistances up to 1000 ohms, a vacuum source such as a hand SPC test pump, a few feet of 5/32" vacuum hose, and several jumper wires.

1. CONTROL SWITCH TEST

A. First, test pin #9 (yellow wire) for ignition voltage (12V).

B. Remove the cruise control module from its mounting position such that it is accessible and still connected to its wiring harness. In this test the wires will be referred to by their position in the white plastic wiring connector, starting with the black ground wires as pin #1 and counting to the other end which is pin #9.

C. Set the V.O.M. (Volt-Ohm-Meter) to read 15 Volts, D.C., near the center of the meter scale. Ground the negative lead of the V.O.M. to the vehicle chassis. Connect the positive lead of the V.O.M. to the cruise module pin #2 accessible at the wire end of the white plastic wiring connector. With the OFF/ON/RESUME switch in the "OFF" position, the V.O.M. should read zero. Slide the "SET" switch on the control handle to the "SET" position. The V.O.M. should indicate IGN. voltage (12V) as long as the "SET" position is held. Next, release the "SET" switch and slide the OFF/ON/RESUME switch to the "RESUME" position. Again, the V.O.M. should read IGN. voltage as long as the "RESUME" position is held.

D. Connect the positive lead of the V.O.M. to pin #3 of the white plastic module connector. With the OFF/ON/RESUME switch in the "OFF" position, the V.O.M. should read zero. Slide the OFF/ON/RESUME switch to the "ON" position. The V.O.M. should read IGN. voltage and should also read IGN. voltage (12V) in the "RESUME" position. With the OFF/ON/RESUME switch in the "ON" position, depressing the "SET" button should cause the V.O.M. to read zero.

E. Connect the positive lead of the V.O.M. to pin #5 of the white plastic module connector. With the OFF/ON/RESUME switch in the "OFF" position, the V.O.M. should read zero. With the OFF/ON/RESUME switch in the "ON" or "RESUME" positions, the V.O.M. should read IGN. voltage.

F. If the switch fails any of the above tests, test for continuity of electrical connectors and, if the connections are good, replace the switch.


2. BRAKE SAFETY SWITCH CHECK

A. Set the V.O.M. as above and connect the negative lead to a good chassis ground. Turn the ignition switch to "ON" position. Place the speed control "OFF/ON/RESUME" switch to the "ON" position.

B. With the positive lead of the V.O.M., check the connection at the wire end of the 4-pin brake switch connector on the connection to the white/red and white wires. Both should have IG N. voltage. If only one terminal has IGN. voltage operate the brake pedal to check that the switch is adjusted so that a click is heard just before the brake pedal arm comes back to the return stop. If adjustment is required, refer to the vehicle technical service manual for correct adjustment procedure. Also check to see that the connectors are plugged in fully. If adjustment cannot be accomplished to get the results in step 2, replace the brake switch. If there is no voltage on either of the two wires, check speed control fuse.

C. On the same connector, check the connections to the dark blue/red and dark blue wires. There should be 0 to 1/2 volt on each of these wires. When the pedal is depressed, the connection to the dark blue wire should be +6 volts, the dark blue/red should stay at zero.

3. CLUTCH SAFETY SWITCH (Manual Transmission Only)

A. Turn the ignition switch to the "ON" position and the speed control "OFF/ON/RESUME" switch to the "ON" position. Connect the negative lead of the V.O.M. to a good chassis ground.

B. With both the brake and clutch pedals in the returned position, both leads on the clutch switch should read zero with the V.O.M. Connect the positive lead of the V.O.M. to the pin with the dark blue/red wire on the clutch switch connector. With the clutch pedal depressed this pin should read +6 volts.

C. If the above result cannot be achieved, insure that clutch switch position is adjusted so that it operates when the clutch pedal is depressed. If unable to cause this, clutch switch is defective. Replace.

4. SPEED SENSOR TEST

A. Disconnect the lower speedometer cable at the speed sensor.

B. The distance (speed) sensor should generate eight pulses per revolution. To check the sensor, use an ohmmeter on the LOWEST scale (Example: 0-2) so readings of less than 1 ohm will show clearly.

C. Disconnect the two way bullet connector and attach the ohmmeter to both terminals of the speed sensor. Rotate the speed sensor core at the transmission end.

D. Each pulse should have a value of 0.5 (1/2) ohm or less. Anything over this specification indicates too much resistance in the distance (speed) sensor reed switch contacts.

E. Reconnect the speedo cable and wiring assembly.

NOTE: Make sure ohmmeter is calibrated before performing test.

CAUTION: To avoid damage to speed sensor, do not use test lamp to check speed sensor.


5. VALVE BODY AND VACUUM MOTOR TEST

A. Turn ignition switch "ON" and speed control switch "ON". With V.O.M., set-up to measure IGN. voltage (12V), connect the negative lead of the V.O.M. to a good chassis ground.

B. Disconnect the four one-way "bullet" style connectors (bullet colors - yellow, black, red, black) going to the valve body. With the ignition switch "ON" and the OFF/ON/RESUME switch "ON", the female valve body connectors with the white/red wire should measure IGN. voltage on the V.O.M. If not, the harness is defective or there is a loose connection.

C. Re-connect the white/red wired connector to the valve body. Now the other three female valve body connectors should all measure IGN. voltage with the V.O.M. If this cannot be done, the valve body is defective, replace.

D. Disconnect the hose connection from the vacuum servo-motor to the valve body and connect the hand vacuum test pump directly to the vacuum servo motor. CAUTION: Be sure engine is OFF before completing this test as otherwise severe engine damage may result. With the hand test pump, apply at least 10 in. Hg. of vacuum to the servo and note that the throttle is fully applied. If this cannot be done, either servo or mechanical throttle linkage is defective. Replace, re-adjust as necessary.

E. Re-connect the servo hose to the valve body and connect the vacuum hand pump to the inlet side of the vacuum reservoir. Pump 10 in. Hg. into the reservoir.

F. With jumper wires connect the female valve body electrical connectors with black and yellow/white wires to ground. Momentarily connect the connector with the brown wire to ground. This should cause the servo to operate and hold. Removing the ground connection from either the black or the yellow/white wires should cause the throttle to release. Both tests should be made. If this test cannot be accomplished, the valve body is defective. Replace. NOTE: A very slow leak-down or leak-up of the
throttle servo position over the period of 2 or 3 minutes is acceptable. Any leakage rate faster than this indicates unacceptable valve body leakage.

G. Reconnect all valve body wires and reconnect vacuum hose to reservoir.


6. MODULE TEST

Electronic modules very seldom cause erratic performances and should not be replaced if speed can be maintained within +/- 5 mph of the selected speed on a level road.

A. Control switch, brake (and clutch if applicable) safety switches, speed sensor and valve body/vacuum system should be tested prior to this test.

B. Set up the V.O.M. to read IGN. voltage (12V), D.C. Connect the negative lead of the V.O.M. to a good chassis ground. Connect the positive lead to the module connector connection on pin 7.

C. Start the car and drive at a speed of from 40 to 50 mph.

D. Turn the speed control switch to "ON". The V.O.M. should indicate IGN. voltage.

E. Press the speed control switch "SET" button and release. The V.O.M. should indicate from +5 volts to +9 volts and will probably fluctuate one or two volts at a fairly rapid rate. The Speed Control System should be performing throttle control at this time to maintain the "SET" speed satisfactorily. If not, replace the electronic module.



ELECTRONIC SPEED CONTROL SYSTEM INSTALLATION DIAGRAM