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Home >> GMC >> 2003 >> Safari Van Cargo, AWD >> Repair and Diagnosis >> External Pages >> Different car >> Section 73 (Automatic Transmission Diagnosis - 4L80-E (Gasoline)) >> Diagnostic Tests >> DTC P0503: Output Speed Sensor Circuit - Intermittent >> Circuit Description

Circuit Description

WARNING: This page is about a different car, the 2002 GMC Cab & Chassis Sierra and 2002 Chevrolet Cab & Chassis Silverado. However, it is still accessible from the selected car via links, so may be relevant.

The OSS, which is a permanent magnet generator, provides the vehicle speed information to the PCM. The permanent magnet generator produces a pulsing AC voltage as the transmission speed sensors rotor teeth pass through the sensor's magnetic field. The AC voltage level and the number of pulses increase as the speed of the vehicle increases. The PCM then converts the pulsing voltage to a digital signal for vehicle speed. The vehicle speed is used for engine and transmission calculations.

If the PCM detects a low vehicle speed and there is a high engine speed in a drive gear range, DTC P0503 sets. For Federal emissions, DTC P0503 is a type "C" DTC. For California emissions, DTC P0503 is a type "B" DTC.

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