Quote:
Originally Posted by MetroMPG
Depeding on the OBD-II protocol your vehicle uses, cutting the ignition may cause a ScanGauge to shut down and take an unacceptably long time to re-initialize after you turn the power back on again. During that time, it's not recording speed/distance, and over time will skew the SG data and become a pain in the butt.
The ISO protocol in the Metros is one like this.
The other kill switch methods stop the engine witnout interrupting power to the SG, so it continues happily factoring speed/distance into the MPG calcs while instant MPG sits at "9999" (the SG value for 0 fuel use.)
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Well, that and I wouldn't want to power cycle the ECU any more often than necessary...