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Home >> Chevrolet >> 2016 >> Spark LS, Automatic CVT Trans >> Repair and Diagnosis >> External Pages >> Different car >> Section 23 (Data Communication System) >> Diagnostic Information and Procedures >> DTC U0074: Control Module Communication Bus B Off >> Circuit/System Testing >> Testing the Serial Data Circuits for a Short to Ground
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Testing the Serial Data Circuits for a Short to Ground

WARNING: This page is about a different car, the 2015 Chevrolet Spark. However, it is still accessible from the selected car via links, so may be relevant.
  1. Ignition OFF, all access doors closed, all vehicle systems OFF and all keys at least 3 m (9.8 ft) away from vehicle. It may take up to 2 minutes for all vehicle systems to power down.
  2. Disconnect the harness connectors with the chassis high speed GMLAN serial data circuits at an easily accessible device.
  3. Test for greater than 100 Ω between each serial data circuit at the device connector that was just disconnected and ground.
    • If each serial data circuit is 100 Ω or greater 

      Replace the device that was disconnected.

    • If any serial data circuit is less than 100 Ω 
  4. Disconnect the harness connectors with the chassis high speed GMLAN serial data circuits at another device, in the direction of the circuit shorted to ground.
  5. Test for greater than 100 Ω between each serial data circuit at the device connector that was just disconnected and ground.
    • If both serial data circuits are 100 Ω or greater 

      Replace the device that was disconnected.

    • If any serial data circuit is less than 100 Ω 
  6. Repeat step  4 until one of the following conditions are isolated:
    • A short to ground on the serial data circuit between two devices or splice packs, if equipped.
    • A short to ground on the serial data circuit between a device and a terminating resistor.
    • A short to ground on the serial data circuit between the X84 Data Link Connector and the first device or splice pack.