Symptom Diagnosis Description

Symptom Diagnosis Description
Certain circumstances and system limitations will produce 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 navigation system symptoms.

Self-Inertial Navigation Limitations
The limitations of the self-inertial portion of the navigation system (the yaw rate sensor and the vehicle speed sensor) can cause some discrepancies between the actual vehicle position and the indicated vehicle position. If there is a large discrepancy, and the system is receiving GPS signals, the system will adjust the indicated vehicle position to the GPS vehicle position. However, if GPS signals cannot be received, you must tune the vehicle position manually.

The following circumstances may cause vehicle positioning errors until the system can adjust to the GPS.

* Moving the vehicle with the engine 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:
- Continuous tire slippage on a slippery surface.
- Driving with snow chains mounted.
- Abnormal tire pressures.
- Different diameter tires.
- Frequent lanes changes across a wide highway.
- Continuous driving on a straight or gently curving highway.

Tolerances in the system and map accuracy sometimes limit how precisely the vehicle position is indicated.

Examples of this include:
- Driving on roads not shown on the map (map matching is not possible).
- Driving on a road that winds in one direction, such as a loop bridge, an interchange, or a spiral parking garage.
- Driving on a road with a series of sharp hair-pin turns.
- Driving on one of two close parallel roads.
- After making many 90 degree turns.

Global Positioning System (GPS) Limitations
The GPS cannot detect the vehicle position in these instances:
- For the first five to ten minutes after reconnecting the battery.
- When the satellite signals are blocked by tall building, mountains, tunnels, large trees, or large trucks.
- When the GPS antenna is blocked by something on the package shelf.
- When there is no satellite signal output. (Signal output is sometimes stopped for satellite servicing.)

The precision of the GPS is reduced in these instances:
- When only two satellite signals can be received. (Three satellite signals are required for accurate positioning.)
- When the satellite control center purposely lowers the signal precision.

LCD Display Unit Limitations
In cold temperatures, the display may stay dark for the first two or three minutes until it warms up.

When the display is too hot because of direct summer sunlight, it will remain dark until the temperature drops.

When the humidity is high and the interior temperature is low, the display may appear cloudy. The display will clear after some use.

Fingerprints on the touch panel may sometimes be noticeable because of the panel's low-reflection coating. When cleaning the panel, wipe it gently with a soft cloth. To avoid scratching the panel, do not rub too hard.

The touch panel is an infrared system, so there is no need to press hard. If a touch switch does not function immediately, shift your finger slightly on the switch, and touch it again.

Symptom Duplication
When the symptom can be duplicated, follow the self-diagnostic procedures (picture diagnosis mode) and the appropriate troubleshooting procedures.

When the symptom does not reappear or only reappears intermittently, ask the customer about the conditions when the symptom occurred.
- Try to establish if outside interference may have been the cause.
- Try to duplicate the symptom under the same conditions the customer was experiencing.
- Vibration, temperature extremes, and moisture (dew, humidity) may be factors that are difficult to duplicate.