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Home >> Lincoln >> 2009 >> MKX FWD >> Repair and Diagnosis >> External Pages >> Different car >> Section 2148 (Information Center - Instrumentation, Message Center And Warning Chimes) >> Diagnosis And Testing >> Instrumentation, Message Center and Warning Chimes >> Pinpoint Tests >> Pinpoint Test I: Inaccurate Speedometer Indication >> Normal Operation

Normal Operation

WARNING: This page is about a different car, the 2010 Lincoln MKX and 2010 Ford Edge. However, it is still accessible from the selected car via links, so may be relevant.

The PCM calculates the vehicle speed from the transaxle Output Shaft Speed (OSS) sensor input and from the tire size and axle ratio configuration in the PCM Vehicle Identification (VID) block. The PCM provides the Instrument Cluster (IC) with the vehicle speed data over the High Speed Controller Area Network (HS-CAN) bus. The IC  monitors the vehicle speed input and commands the speedometer with a corresponding movement of the pointer.

The IC  provides a tolerance which biases the speed indication and allows the gauge to display between 3% lower and 7% higher than the actual vehicle speed. This means that with an actual vehicle speed of 96.6 km/h (60 mph), the speedometer may indicate between 93.7-103.3 km/h (58.2-64.2 mph). Other factors that can potentially affect the speedometer accuracy are incorrect tire size, tire size configuration and axle ratio configuration.

If the IC  does not receive the vehicle speed data from the PCM for 5 seconds or less, the IC  defaults the speedometer to the last setting, based upon the last known good vehicle speed message. If the IC  does not receive the vehicle speed data from the PCM for more than 5 seconds or if the data received is deemed invalid, the IC  sets DTC U0100 in continuous memory and defaults the speedometer to 0 km/h (0 mph).

NOTE: If DTC U0100 is set in the IC  , other observable symptoms may be an inoperative tachometer, temperature gauge or odometer.

This pinpoint test is intended to diagnose the following: 

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