Symptom Diagnosis

Certain circumstances and system limitations may result in occasional vehicle positioning errors. Some customers may think this indicates a problem with the navigation system when, in fact, the system is normal. Keep the following items in mind when interviewing customers about symptoms of the navigation system.

Self-Inertial Navigation Limitations 

The limitations of the self-inertial portion of the navigation system (the gyro and the vehicle speed signal) can cause discrepancies between the vehicle's actual position and the indicated vehicle's position (GPS vehicle position).

The following circumstances may cause vehicle positioning errors:

• Moving the vehicle with the engine stopped and the vehicle stopped, such as by ferry or tow truck, or if the vehicle is spun on a turn table.
• Tire slippage, changes in tire rolling diameters, and some driving situations may cause discrepancies in travel distances. Examples of this include;
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    Continuous tire slippage on a slippery surface

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    Driving with snow chains mounted

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    Abnormal tire pressure

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    Incorrect tire size

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    Frequent lane changes across a wide highway

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    Very bumpy roads

• Tolerances in the system and map inaccuracies sometimes limit how precisely the vehicle's position is indicated. Examples of this include;
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    Driving on roads not shown on the map (map matching is not possible)

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    Driving on a road that winds in one direction, such as a loop bridge, an interchange, or a spiral parking garage

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    Driving on a road with a series of sharp hair-pin turns

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    Driving near a gradual highway exit or transition

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    Driving on one of two close parallel roads

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    Making many 90 degree turns

Global Positioning System (GPS) Limitations 

The GPS cannot detect the vehicle's position or elevation during the following instances:

• For the first 5 to 10 minutes after reconnecting the 12 volt battery (this process can take as long as 45 minutes).
• When the satellite signals are blocked by tall buildings, mountains, tunnels, large trees, inside parking structures or large trucks.
• When the GPS antenna is blocked by metallic window tinting or by an object placed above it in the vehicle. The GPS antenna requires a clear unobstructed view of the sky.
• When there is no satellite signal output (signal output is sometimes stopped for satellite servicing).
• When the satellite signals are blocked by the operation of some electronic aftermarket accessories including, but not limited to non-OEM in-dash entertainment units (amp, CD players/changers, radar detectors, theft recovery systems, etc.) and cell phones placed near the navigation system.

The accuracy of the GPS is reduced during these instances:

• Metallic window tinting above the GPS antenna.
• When only three or fewer satellite signals are received (Four satellite signals are required for accurate positioning).
• When driving near high tension power lines.
• When the satellite signals are blocked by the operation of some electronic aftermarket accessories including, but not limited to non-OEM in-dash entertainment units (amp, CD players/changers, radar detectors, theft recovery systems, etc.) and cell phones placed near the navigation system.
• When the satellite control centers are experiencing problems.

LCD Unit Limitations 

The center display unit is touch sensitive. Touch the display directly to select items on the screen.

• Heavy gloves, fingernails or pens cannot be used on the touch panel.
• In cold temperatures, the display may stay dark for the first minute until it warms up.
• When the display is too hot because of direct summer sunlight, it remains dark until the temperature drops (you may see an error message displayed stating this fact).
• Fingerprints on the screen may be noticeable. Clean the screen with a soft, damp cloth. You may use a mild cleaner intended for eye glasses or computer screens. To avoid scratching the panel, do not rub too hard or use abrasive cleaners or shop towels.