SYMPTOM RELATED DIAGNOSTICS

ENGINE BRAKE VERBAL COMPLAINT (continued)

Test 128

Checking for signal voltage from V-MAC

If the voltage on ONE of pins 85 OR 86 is 12 volts or more (but not both) while the engine decelerates, repeat this test with all of the remaining engine brake relays. If all of the relay test results lead to this step, proceed to Test 256.

If pin 85 AND pin 86 both measure 0 volts while the engine decelerates, proceed to Test 257.

Test 256

Checking for a bad brake relay connector

1.Start the engine. Using the engine speed control ON/OFF and SET switches, set the engine speed to 1800 rpm.

2.Connect multimeter probes to pin 85 of one brake relay connector and to a good ground.

3.While measuring the voltage between pin 85 and ground, turn the Speed Control ON/OFF switch to the OFF position. Record the voltage as the engine decelerates.

4.Repeat this procedure for pin 86 of the same engine brake relay connector.

1.Turn the ignition key to the OFF position.

2.Visually inspect each engine brake relay connector terminals for corrosion, shorts to other terminals, bent terminals or signs of poor contact.

If there are visible problems, repair or replace the relay connector and test the engine brake operation.

If there are no visible problems, reinstall the relay(s) and test the engine brake.

If the engine brake works properly, the procedure has corrected the problem. Check all connections.

If the engine brake still does not work properly, proceed to Test 512.