GM Service Manual Online
For 1990-2009 cars only

Diagnostic Instructions

    • Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure.
    • Review Strategy Based Diagnosis for an overview of the diagnostic approach.
    •  Diagnostic Procedure Instructions provides an overview of each diagnostic category.

DTC Descriptors

DTC U0100 00: Lost Communication With Engine/Powertrain Control Module (ECM/PCM)

DTC U0101 00: Lost Communication With Transmission Control Module (TCM)

DTC U0102 00: Lost Communication With Transfer Case Control Module

DTC U0104 00: Lost Communication With Cruise Control Module

DTC U0121 00: Lost Communication With Electronic Brake Control Module (EBCM)

DTC U0140 00: Lost Communication With Body Control Module (BCM)

DTC U0151 00: Lost Communication With Sensing and Diagnostic Module (SDM)

DTC U0151 71: Lost Communication With Restraints Control Module Invalid Serial Data Received

DTC U0151 7F: Lost Communication With Restraints Control Module Erratic

DTC U0155 00: Lost Communication With Instrument Panel Cluster (IPC) Control Module

DTC U0164 00: Lost Communication With HVAC Control Module

DTC U0168 00: Lost Communication With Vehicle Theft Deterrent (VTD) Control Module

DTC U0170 00: Lost Communication With Passenger Presence System (PPS)

DTC U0184 00: Lost Communication With Radio

DTC U0194 00: Lost Communication With Digital Radio Receiver (DRR)

DTC U0198 00: Lost Communication With Communication Interface Module (OnStar®)

DTC U0209 00: Lost Communication With Heated Seat Module (HSM)

DTC U0214 00: Lost Communication With Remote Function Actuator (RFA)

DTC U2105 00: Lost Communication

Diagnostic Fault Information

Circuit

Short to Ground

Open/High Resistance

Short to Voltage

Signal Performance

Low speed GMLAN serial data

1

U0140-U0214

1

--

Battery positive voltage circuits

U0100- U0214

U0100- U0214

--

--

Ignition voltage circuits

U0100- U0214

U0100- U0214

--

--

Module ground circuits

--

U0100- U0214

--

--

Accessory Wakeup serial Data

U1814

U0100, U0101

--

--

Serial Data Communication Enable

U2099

U0121

--

--

1. Scan Tool Does Not Communicate with Low Speed GMLAN Device

Circuit/System Description

Modules connected to the high and low speed GMLAN serial data circuits monitor for serial data communications during normal vehicle operation. Operating information and commands are exchanged among the modules. The modules have prerecorded information about what messages are needed to be exchanged on the serial data circuits, for each virtual network. The messages are supervised and also, some periodic messages are used by the receiver module as an availability indication of the transmitter module. Each message contains the identification number of the transmitter module.

The body control module (BCM) activates the serial data communication enable and the accessory wakeup serial data circuits by applying voltage 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 and the accessory wakeup serial data circuit wakes up the engine control module (ECM) and transmission control module (TCM)

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

A supervised periodic message that includes the transmitter module availability has not been received.

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.

Reference Information

Schematic Reference

    •  Data Communication Schematics
    •  Control Module References

Connector End View Reference

Data Communication Connector End Views

Electrical Information Reference

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