8206noco.fm Page 177 Thursday, July 2, 1998 1:19 PM
SYMPTOM RELATED DIAGNOSTICS BUFFERED MPH (continued) Test 2
1. Turn the ignition key to the OFF position.
Checking for 12 volts and ground to speedometer
2. Disconnect the J1B connector from the V-MAC II module. 3. Disconnect the speedometer connector. 4. Connect the serial link jumper into the serial communication port. 5. On the harness side of the speedometer connector, check for 12 volts on the supply (power) line. 6. Disconnect the serial link jumper. 7. Check for continuity from the connector ground to a good ground.
If both supply and ground are present, proceed to Test 4. If 12-volt supply or ground are not present, locate and repair the missing supply or ground. Retest to be sure the problem has been corrected.
Test 4 Checking for voltage on the buffered MPH line in the harness 1. Connect the serial link jumper into the serial communication port.
Figure 293 — Speedometer Connector
2. Measure the voltage on the buffered MPH line on the harness side of the speedometer connector.
If the voltage is greater than 0.5 volts, the buffered MPH line is shorted to voltage in the harness or connector. Repair the short and retest to be sure the problem has been corrected. If the voltage is less than 0.5 volts, proceed to Test 8.
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