FILTER ELEMENT AS-AIR 2525001 - Caterpillar

System Operation Description:The ECM uses vehicle speed information for the following features:
Cruise control
PTO operation
Fuel economyAn incorrect "Vehicle Speed Calibration" will cause fuel economy data that is stored in the ECM to be incorrect. An incorrect "Vehicle Speed Calibration" will cause fuel economy data that is calculated by using an ECM driven speedometer to be incorrect.The ECM calculates vehicle speed by converting the vehicle speed signal to kilometers per hour (km/h) or to miles per hour (mph). The conversion factor is customer programmable and the conversion factor is stored in pulses per km (PPKM) or pulses per mile (PPM).Note: The ECM speedometer signal is set to 18,600 pulses per km (PPKM) or 30,000 pulses per mile (PPM). This setting cannot be changed. All speedometers that are driven by the ECM must be set to 30,000 PPM for proper operation.Test Step 1. Calculating Pulses Per Kilometer (Mile) When all the Variables are Known.
Calculate pulses per kilometer (PPKM) or pulses per mile (PPM). PPKM = K X Ra X N.PPM = M X Ra X N.K - This symbol represents the tire revolutions per kilometer. This is a constant that is divided by the tire static loaded radius.M - This symbol represents the tire revolutions per mile. This is a constant that is divided by the tire static loaded radius.Ra - This symbol represents the rear axle ratio. The rear axle ratio can typically be found on the housing of the rear axle, or the rear axle ratio can typically be found on the specification sheet for the vehicle.N - This symbol represents the number of chopper teeth on the transmission drive shaft. The magnetic pickup sensor is mounted here. The number of chopper teeth is usually 16. Some transmissions have 11 tooth chopper wheels.
Use the electronic service tool to enter pulses per km (PPKM) or pulses per mile (PPM) into the ECM.Expected Result:This value is within the valid range of the ECM.Results:
OK - Once the value is entered, verify that the ECM is accurately measuring vehicle speed. Proceed to Test Step 2.
Not OK - Recalculate the value and re-enter the correct value into the ECM. Stop.Test Step 2. Inspect the Speedometer Calibration.Determine the speedometer's vehicle speed calibration setting.Expected Result:The speedometer must be calibrated to 18,600 pulses per kilometer (30,000 pulses per mile).The ECM can only provide the signal that is listed above. Results:
OK - The speedometer is correctly calibrated. Stop.
Not OK - Repair: Perform the following diagnostic procedure:Reprogram the speedometer to the correct setting for the pulses per kilometer (mile). Stop.