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 Descriptor

DTC U1817 00: Lost Communication With Hybrid Powertrain Control Module on Bus "B"

Diagnostic Fault Information

Circuit

Short to Ground

Open/High Resistance

Short to Voltage

Signal Performance

PTLAN + (circuit 6105)

U0074*

U1817* **, U189A in HPCM, U182A in SDGM

U0074*

--

PTLAN - (circuit 6106)

U0074*

U1817* **, U189A in HPCM, U182A in SDGM

U0074*

--

* Other modules/DTCs will set with this fault.

** This DTC may set in the ECM or the SDGM.

Circuit/System Description

Modules connected to the PTLAN 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.

Conditions for Running the DTC

    • The system voltage is between 9-16 volts.
    • The vehicle power mode master requires serial data communication to occur for this specific module.

Conditions for Setting the DTC

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

Action Taken When the DTC Sets

The modules is never signaled, therefore the specific subsystems will not function.

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.

Circuit/System Verification

With a scan tool, ensure the following DTCs are not present in the modules as follows:

HPCM

U189A

SDGM

    • U182A
    • U0074

If any listed DTC is present, refer to Diagnostic Trouble Code (DTC) List - Vehicle to diagnose that DTC.