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Home >> Cadillac >> 2018 >> Escalade Base, 4WD >> Repair and Diagnosis >> External Pages >> Different car >> Section 16 (Transfer Case - Mp 3010 (NP0)) >> Diagnostic Information And Procedures >> DTC P17D4, P185F, P279A, P279B, P279C: Transfer Case (L83) >> Circuit/System Description

Circuit/System Description

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The ECM uses two ways to determine if the transfer case is in 4WD Low, 4WD High or Neutral.

  1. Compare the transmission output speed sensor (Transmission OSS) to the transfer case output speed sensor (Transfer Case OSS - parameter name inside ECM) (B115 Vehicle Speed Sensor - component code name in Schematics) in order to calculate transfer case range.
  2. Use a LAN message sent by the transfer case shift control module to the ECM.

The ECM uses this message to determine motor torque required and transmission shifting.

The internal fault detection is handled inside the control module. No external circuit diagnosis is involved.

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