SYMPTOM RELATED DIAGNOSTICS

ENGINE BRAKE VERBAL COMPLAINT (continued)

If the relay shows continuity to ground through pin 85 or pin 86, but not both, repeat the test with all remaining engine brake relays. If all of the relay test results lead to this step, proceed to Test 16.

If neither pin 85 or 86 show continuity to ground, proceed to Test 17.

Test 10

Checking for an open pressure switch

If the vehicle is not equipped with an inlet manifold pressure switch, proceed to Test 80.

1.Disconnect the inlet manifold pressure switch from the harness.

2.With the ignition key in the OFF position, check for continuity across the switch terminals.

If there is continuity, proceed to Test 20.

If there is no continuity, replace the switch. Retest to be sure the problem has been corrected.

Test 16

Checking for a short to other wires

3.Check for continuity between J1B connector pin P3 (the engine brake relay control line) and each of the other pins (one at a time) on the J1A, J1B and J2 connectors.

If there is no continuity, proceed to Test 32.

If pin P3 is shorted to any other pin in the harness, find and repair the short. Retest to be sure the problem has been corrected.

Test 17

Checking for an open dash switch

1.Remove the dashboard switch to expose the switch terminals.

2.Locate the switch terminals leading to the relay which showed no continuity to ground in the previous test.

3.With the engine brake dash switch in the ON position, check for continuity across the switch terminals.

If there is no continuity, replace the switch. Retest to be sure the problem has been corrected.

If there is continuity, proceed to Test 34.

Test 20

Checking for a short to ground in the pressure switch

1.Check for continuity from either of the pressure switch leads to a good ground.

If there is continuity, repair or replace the switch. Retest to be sure the problem has been corrected.

If there is no continuity, proceed to Test 40.

1.Turn the engine brake switch on the dashboard to the OFF position.

2.Disconnect the J1A and J2 connectors from the V-MAC II module.