8206noco.fm Page 212 Thursday, July 2, 1998 1:19 PM
SYMPTOM RELATED DIAGNOSTICS SWITCH CIRCUIT FAILURE (continued) Test 4
Test 17
Checking for stray voltage at the module
Checking for voltage to the switch
1. Turn the ignition key to the ON position.
1. Turn the ignition key to the OFF position.
2. With the switch OFF, measure the voltage from the pin at the V-MAC II module connector to a good ground.
2. Disconnect the wire leading from the switch terminal to the V-MAC II module at the switch terminal.
If the voltage is greater than 0.5 volts, proceed to Test 9.
3. Turn the ignition key to the ON position.
If the voltage is less than 0.5 volts, proceed to Test 8.
4. Measure the voltage at the switch voltage supply terminal to a good ground.
If 12 volts are present, proceed to Test 34.
Test 8 Checking switch voltage at the module 1. With the switch ON, measure the voltage from the pin at the V-MAC II module connector to a good ground.
If 12 volts are not present, there is a loss of power to the switch. Locate and repair the problem. Retest to be sure the problem has been corrected.
Test 19
If the voltage is greater than 10 volts, replace the V-MAC II module. Retest to be sure the problem has been corrected.
Checking for a short in the harness
If the voltage is less than 10 volts, proceed to Test 17.
2. Disconnect the remaining V-MAC II module connectors.
Test 9
3. Check for continuity between the switch signal pin and each of the other pins (one at a time) on the J1A, J1B and J2 connectors.
Checking for a short to voltage in the harness 1. Turn the ignition key to the OFF position. 2. Disconnect the wire supplying 12 volts to the switch at the switch terminal. 3. Turn the ignition key to the ON position. 4. Measure the voltage from the V-MAC II module connector pin to a good ground.
If 12 volts are present, proceed to Test 19. If 12 volts are not present, examine the switch for bent or damaged pins that would cause a short to voltage. Repair the pins or replace the switch. Retest to be sure the problem has been corrected.
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1. Turn the ignition key to the OFF position.
If there is continuity with another pin, locate and repair the short in the harness. Retest to be sure the problem has been corrected. If there is no continuity, there is a short to voltage somewhere else in the cab or dashboard, between the switch and the V-MAC II module. Locate and repair the short to voltage. Retest to be sure the problem has been corrected.
