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For 1990-2009 cars only
Makes 🢒 Chevrolet 🢒 2006 🢒 Impala 🢒 Vehicle Control Systems 🢒 Vehicle DTC Information 🢒 DTC U2099

DTC Descriptor

DTC U2099 00: High Speed Communication Enable Circuit

Diagnostic Fault Information

Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure.

Circuit

Short to Ground

Open/High Resistance

Short to Voltage

Signal Performance

Serial Data Communication Enable

U2099, U0100-U0299¹

U0100-U0299

U0100-U0299²

--

¹ Vehicle will not start.

² History only. If cleared the DTC will return after several ignition cycles.

Typical Scan Tool Data

HS Comm. Cmd.-BCM

Circuit

Normal Range

Short to Ground

Open

Short to Voltage

Operating Conditions: Ignition Switch in ACC or RUN

Serial Data Communication Enable

On

Off

On

On

Operating Conditions: Ignition Switch in OFF

Serial Data Communication Enable

Off

Off

Off

On

Circuit/System Description

The body control module (BCM) activates the serial data communication enable circuit, when the ignition key is in ACC, ON or START. The serial data communication enable circuit wakes up the electronic brake control module (EBCM) for buss communication.

Conditions for Running the DTC
    • The system voltage is between 9-16 volts.
    • The vehicle power mode master requires serial data communication to occur.

Conditions for Setting the DTC

The BCM senses a short to ground on the serial data communication enable circuit.

Action Taken When the DTC Sets
    • The output command is turned off while the malfunction is present.
    • The modules use a default value for the missing parameters until the next ignition cycle.
    • The module(s) is never signaled, therefore the specific subsystem(s) will not function.
    • The vehicle will not start while the circuit is shorted to ground.

Conditions for Clearing the DTC
    • A current DTC clears when the malfunction is no longer present.
    • A history DTC clears when the module ignition cycle counter reaches the reset threshold of 50, without a repeat of the malfunction.

Diagnostic Aids
    • Use the DMM MIN/MAX function to capture/locate intermittent conditions.
    • Short to ground will also set multiple history no communication codes for GMLAN high speed modules.

Reference Information

Schematic Reference

    •  Body Control System Schematics
    •  Data Link Connector Schematics

Connector End View Reference

    •  Computer/Integrating Systems Connector End Views
    •  Master Electrical Component List

Electrical Information Reference

    •  Circuit Testing
    •  Connector Repairs
    •  Testing for Intermittent Conditions and Poor Connections
    •  Wiring Repairs

Scan Tool Reference

    •  Scan Tool Data List
    •  Scan Tool Data Definitions

Circuit/System Verification

Use the scan tool to observe the HS Comm. Cmd. parameter in the BCM data list/outputs with the driver door open and key out of the ignition, and with the ignition in the RUN position. The reading should match the normal range of the typical scan tool data above.

If all parameters are correct and the DTC is current, replace the BCM.

Circuit/System Testing
  1. Ignition OFF, disconnect the harness connector at the EBCM.
  2. Retest for current DTCs. DTC U2099 should remain current.
    3. ⇒If the DTC becomes history, replace the EBCM.
  3. Ignition OFF, disconnect the harness connector at the BCM.
  4. Test for infinite resistance between the serial data communication enable circuit and ground.
    5. ⇒If less than infinite resistance, repair the enable circuit for a short to ground.
  5. If all tests normal, replace the BCM.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

Refer to Control Module References for module replacement, setup, and programming.