U0111

DTC U0100-U0299 (HP2)

CIRCUIT DESCRIPTION
Modules connected to the high speed GMLAN serial data circuits monitor for serial data communications during normal vehicle operation. There are two 120 ohm resistors between the GMLAN serial data (+) and (-) circuits. One is internal to the powertrain control module (PCM) and the other is internal to the energy storage control module (ESCM). When tested between the GMLAN serial data (+) and (-) circuits at the DLC with the ignition key OFF, normal resistance is 55-65 ohms.

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. 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. When a message that indicates the availability of the transmitter module is not received, the receiver module sets a DTC.

DTC DESCRIPTORS
This diagnostic procedure supports the following DTCs:
- DTC U0111 Lost Communication With Energy Storage Control Module (ESCM)
- DTC U0120 Lost Communication With Starter/Generator Control Module (SGCM)
- DTC U0131 Lost Communication With Electro-Hydraulic Power Steering (EHPS) Module
- DTC U0293 Lost Communication With Hybrid Control Module (HCM)

CONDITIONS FOR RUNNING THE DTCs
Voltage supplied to the modules is in the normal operating voltage range.

CONDITIONS FOR SETTING THE DTC
A supervised periodic message that includes the transmitter module availability has not been received by powertrain control module (PCM) from one or more of the high speed GMLAN modules.

ACTION TAKEN WHEN THE DTC SETS
- The MIL may illuminate.
- The Hybrid Engine Idle Off feature may not operate properly.

CONDITIONS FOR CLEARING THE MIL/DTC
- The MIL clears after 3 ignition cycles when the malfunction is no longer present.
- 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, without a repeat of the malfunction.

DIAGNOSTIC AIDS
The following conditions may cause the DTC to set:
- A poor connection or terminal tension at a GMLAN module
- An intermittent open on either high speed GMLAN serial data circuit
- An open voltage or ground circuit to a module
- An internal module malfunction
- A short between the GMLAN serial data circuits
- A short to voltage or ground on either of the GMLAN serial data circuits

TEST DESCRIPTION

Step 1 - Step 6:

Step 7 - Step 13:

Step 14 - Step 16:

The number below refers to the step number on the diagnostic table.
11. A resistance out of range will indicate one of several specific faults as follows:
- A high resistance indicates an open or high resistance in either of the high speed GMLAN serial data circuits between C 206 and the modules, including all module internals, circuits between, and module terminal tension.
- A low resistance indicates a short between the high speed GMLAN serial data circuits, including module internals.
- Infinite resistance indicates an open between the DLC and C 206 in either of the high speed GMLAN serial data circuits.