Scan Tool Does Not Communicate with Low Speed GMLAN Device. Saturn VUE

For 1990-2009 cars only

Makes 🢒 Saturn 🢒 2008 🢒 VUE - FWD 🢒 Power and Signal Distribution 🢒 Data Communications 🢒 Scan Tool Does Not Communicate with Low Speed GMLAN Device

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.

Diagnostic Fault Information

Circuit	Short to Ground	Open/High Resistance	Short to Voltage	Signal Performance
Low Speed GMLAN Serial Data	1	2*	1	--
Ground (DLC, Terminal 5)	--	1	--	--
* An open between the data link connector (DLC) and X 200, or DLC ground terminal 5 will only effect the communication with the scan tool. The vehicle modules will still communicate. 1. No communication on any low speed GMLAN module 2. No communication on a specific low speed GMLAN module

Circuit

Short to Ground

Open/High Resistance

Short to Voltage

Signal Performance

Low Speed GMLAN Serial Data

Ground (DLC, Terminal 5)

* An open between the data link connector (DLC) and X 200, or DLC ground terminal 5 will only effect the communication with the scan tool. The vehicle modules will still communicate.

1. No communication on any low speed GMLAN module

2. No communication on a specific low speed GMLAN module

Modules connected to the low speed GMLAN serial data circuit monitor for serial data communications during normal vehicle operation. Operating information and commands are exchanged among the modules when the ignition switch is in any position other than OFF. The low speed GMLAN serial data circuit must be operational for the vehicle to start so the theft deterrent module (TDM) and body control module (BCM) can communicate. The low speed GMLAN serial data circuit uses JX 200 and JX 209 (splice pack combs) as a common connection between some modules and the DLC.

Diagnostic Aids

•	Use the Data Link References to identify the low speed GMLAN serial data modules.

•	This test is used for a total low speed GMLAN communication failure. If only one module is not communicating and sets no DTC, ensure that the vehicle is equipped with the module, then use DTC U0100-U0299 for diagnostics.

•	An open in the low speed GMLAN serial data circuit between the splice pack and a module will only effect the specific module. This type of failure will set a loss of communication DTC for the module effected, and the other modules will still communicate.

•

An open in the DLC ground circuit terminal 5 will allow the scan tool to operate to set up the vehicle on the tool and then not communicate with the vehicle. When the scan tool is to the point of communicating with the vehicle, a message on the scan tool will indicate "no CANdi module detected" and will not communicate. The vehicle modules will still communicate, and the vehicle will start.

•	An open between the DLC and JX 200 will only effect the communication with the scan tool. The vehicle modules will still communicate, and the vehicle will start.

•	The engine will not start when there is a total malfunction of the low speed GMLAN serial data circuit.

The following conditions may cause a total loss of low speed GMLAN data communication:

•	The low speed GMLAN serial data circuit shorted to ground or voltage.

•	A module internal malfunction that causes a short to voltage or ground on the low speed GMLAN circuit.

Reference Information

Schematic Reference

Data Communication Schematics

Connector End View Reference

•	Component Connector End Views

•	Splice Pack Connector End Views

Description and Operation

Data Link Communications Description and Operation

Electrical Information Reference

•	Circuit Testing

•	Connector Repairs

•	Testing for Intermittent Conditions and Poor Connections

•	Wiring Repairs

Scan Tool Reference

Control Module References for scan tool information

Circuit/System Verification

Attempt to communicate with all modules on the low speed GMLAN bus.

⇒	If any low speed module communicates and any DTC beginning with a U exists, refer to Diagnostic Trouble Code (DTC) List - Vehicle for diagnostics.

Circuit/System Testing

Low Speed GMLAN Initial Test

Test for less than 1.0 ohm between the DLC ground circuit terminal 5 and ground.

⇒	If greater than the specified range, test the ground circuit for open/high resistance.

Ignition OFF, disconnect the harness connector (splice pack comb) at JX209.
Ignition ON, with a scan tool, attempt to communicate with the BCM.

⇒	If communication is available, refer to Diagnostic 2.

⇒	If communication is not available refer to Diagnostic 1.

Diagnostic 1

Ignition OFF, disconnect the harness connector (splice pack comb) at JX200.
Ignition OFF, disconnect the harness connector at the inflatable restraint passenger presence system (PPS) sensor.
Ignition ON, with a scan tool, attempt to communicate with the BCM. Communication should be available.

⇒	If no communication, test the serial data circuit between the DLC, BCM, and the PPS sensor for a short to ground and short to voltage. If the circuit tests normal, replace the BCM.

Ignition OFF, connect the harness connector at the PPS sensor.
Ignition ON, attempt to communicate with the BCM. Communication should be available.

⇒	If no communication, replace the PPS sensor.

Ignition OFF, install a 3-amp fused jumper wire to terminal H of JX200 harness side and terminal G.
Ignition ON, attempt to communicate with the IPC. Communications should be available.

⇒	If communication is not available, test the serial data circuit between the splice pack terminal H and the IPC for a short to ground or a short to voltage. If the circuit tests normal, replace the IPC.

Important: After each connection, cycle the ignition key off for 5 seconds, then ON before attempting to establish communication.

Ignition OFF, with the jumper wire still attached to terminal H, individually move the other end of the jumper wire to each of the terminals listed below and attempt to communicate with the applicable module. Communications should be available with each module listed.

•	Terminal J, radio

•	Terminal E, TDM

•	Terminal C, HVAC control module

•	Terminal D, remote control door lock receiver (RCDLR)

⇒	If any module does not communicate, test the serial data circuit between the applicable module harness connector and the JX200 splice pack connector for a short to ground or a short to voltage. If the circuit tests normal, replace the applicable module.

Diagnostic 2

Ignition OFF, disconnect the harness connector (splice pack comb) at JX200.
Ignition OFF, install a 3-amp fused jumper wire to terminal H of JX200 harness side and terminal C of JX209 splice pack harness side.
Ignition ON, attempt to communicate with the inflatable restraint vehicle roll over sensor. Communication should be available.

⇒	If communication is not available, test the serial data circuit between the JX209 splice pack terminal C and the inflatable restraint vehicle roll over sensor for a short to ground or a short to voltage. If the circuit tests normal, replace the inflatable restraint vehicle roll over sensor.