Operation CHARM: Car repair manuals for everyone.

Principles and Operation

NOTE:
^ The Distance To Empty (DTE) display may be inaccurate if the vehicle is started while parked on an incline.
^ Fuel fills of less than 22.7 liters (6 gallons) may not be detected by the message center.
^ The instantaneous (INST) fuel economy feature is only available on early production vehicles.

The message center uses inputs from the fuel level sensor and pump, the compass sensor module and the Powertrain Control Module (PCM). The input from the PCM is the vehicle speed signal. The PCM gets the vehicle speed signal from the Output Shaft Speed (OSS) sensor.

From those inputs, the message center displays:
^ compass direction.
^ DTE.
^ average (AVG) fuel economy.
^ INST fuel economy (if equipped).

Average (AVG) Fuel Economy - Resetting

NOTE: Only the AVG fuel economy can be reset. DTE and INST displays cannot be reset.

The AVG fuel economy display is resettable. To reset, the ignition switch must be in the RUN position (with or without the engine running) and the message center must be in the AVG fuel economy display mode. Press and release the MODE and E/M buttons simultaneously.

If the vehicle is parked while resetting, the AVG fuel economy will display 0.0 (English mode) or 99.9 (metric mode). If the vehicle is in motion, the AVG fuel economy will display the current INST fuel economy (English mode or metric mode).