Gasboy Fuel Point Vehicle Module - Manual (Page 23)

MDE-4524A Vehicle Module Programming Manual· May 2006 Page 4-9
Odometer Ratio (Enter ODO RATIO) Preparation for Programming
Therefore, the typical odometer ratio for a domestic vehicle is 8000 pulses/mile and for a
foreign vehicle it is 7200 pulses/mile. Use these values for the VM odometer ratio if you are
not sure of the exact values.
Electronic Odometer
On new vehicles, the odometer signal to the VM is tapped off an existing sensor or
speedometer signal from an electronic circuit. Several ways to figure the electronic odometer
ratio are shown below:
• Match working vehicle. If a previously equipped vehicle has accurate odometer data in
the VM, use the same ratio for all other vehicles in the fleet with the same specs.
• Use published ratio. If the VM odometer input is a conditioned signal coming from the
vehicle's computer module or cruise control, the manufacturer's wiring diagram may show
the number of pulses per mile it is generating. These values are typically round numbers
such as 10,000, 20,000, or 40,000.
Figure 4-1
ELECTRONIC CONTROL MODULE (ECM)
VEHICLE
SPEED
INPUT VEHICLE
SPEED
INPUT
VEHICLE
SPEED
INPUT
4000 PULSES
PER MILE 2000 PULSES
PER MILE
IGNITION
INSTRUMENT
CONTROL
CRUISE
MODULE
SPEED
VEHICLE
SENSOR
MAGNET
PERMANENT
GENERATOR
CLUSTER
4000 PULSES
PER MILE
Sample Wiring Diagram. Notice Pulses Per Mile.
• Use engine computer ratio. Today’s over-the-road trucks have smart engines allowing
you to view and adjust many performance parameters through the diagnostic port. If the
VM odometer signal is tapped off from the same signal source as the dashboard
speedometer, you can use the speedometer ratio stored in the engine computer for the VM
odometer ratio.
• Calculate from vehicle specs. If the VM odometer receives input directly from the
speedometer sensor mounted in the transmission, you may be able to calculate the correct
ratio using specs from the vehicle manufacturer.