8206noco.fm Page 182 Thursday, July 2, 1998 1:19 PM
SYMPTOM RELATED DIAGNOSTICS r
When checking the harness, refer to the wiring diagrams in the appropriate Electrical Manual. Check each wire that connects the component to the V-MAC II module for shorts to ground, shorts to power or continuity with other wires. Check for continuity between both ends of the harness and each wire in the harness.
For general V-MAC II troubleshooting, follow the guidelines listed below:
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All “ground check” tests should be performed with a known good ground.
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Verify that the electronic fault and engine shutdown lights work properly. When the key is turned ON, both lamps should light for 2 seconds.
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Continuity checks can not be performed if there is any current flowing. Before performing any continuity checks, make sure that:
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Check for inactive faults, or active faults if the electronic malfunction lamp was replaced. (The Pro-Link retains information from the previous vehicle. Before looking for faults, reset the Pro-Link by activating the RESTART option on the Pro-Link menu.)
INTERMITTENT PROBLEMS This section of the manual is intended to provide troubleshooting tips for intermittent problems. In some instances there may not be a diagnostic blink code or inactive fault logged in the V-MAC II module to assist in troubleshooting.
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Review the “Diagnostic Tools and Procedures” section at the front of this book.
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Start troubleshooting at the sensor, switch, or other device. Then check the harness and finally check the V-MAC II module. Eliminate all other possible faults and repeat the procedure before replacing the V-MAC II module.
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Check sensors, connectors and other components for broken pins, dirt, corrosion, loose terminals, excessive resistance, moisture and bad grounds.
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If a sensor or other component is suspected as being bad, disconnect, clean and reconnect all terminals to that component. Retest to see if the problem has been resolved.
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If a sensor or other component is suspected as being bad, try to isolate it from the system. Often, when a faulty component is removed from the system, the vehicle performance will change. If performance does not change when the component is disconnected, that component may not be the source of the problem.
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– The ignition key is in the OFF position. – The serial link jumper harness is not installed. r
Before disconnecting the harness to the V-MAC II module, the ignition key must be in the OFF position and the serial link jumper harness must not be installed. Failure to follow these instructions may result in internal electrical damage to the module.
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Before turning the ignition key to the ON position with the J1B connector disconnected, always connect the serial link jumper into the serial communication port to provide keyed 12 volts. Turning the ignition key to the ON position with the J1B connector disconnected will not energize the accessory relay and will not provide a keyed 12 volts.
Turning the ignition key to the ON position with a sensor disconnected, or with the J1A connector disconnected while the J1B connector is still connected will result in an active fault. r
If the V-MAC II module is suspected of being defective, verify that there is power from the circuit breaker to the V-MAC II module.
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Do not open the V-MAC II module or take any measurements at the V-MAC II module pins. If a module is suspected of being defective, visually inspect the pins for any repairable problems.
