Scan Tool Does Not Communicate with CAN Device. Saturn VUE

For 1990-2009 cars only

Makes 🢒 Saturn 🢒 2002 🢒 VUE - FWD 🢒 Body and Accessories 🢒 Data Link Communications 🢒 Scan Tool Does Not Communicate with CAN Device

<B> Modules connected to the CAN serial data circuits monitor for serial data communications on the CAN network during normal vehicle operation. Operating information and commands are exchanged among the modules. When a module detects a bus-off condition a DTC U0001 or U2100 will be set. These DTCs can be retrieved as history only.

Diagnostic Aids

The CAN serial data buss uses two 120 ohms terminating resistors that are in parallel with the CAN High and Low circuits. One of the resistors is connected at the data link connector (DLC) end of the link and the other is at the engine management module, engine control module (ECM) or powertrain control module (PCM), end of the link. The other terminating resistor resides internally in the BCM. When testing for a short between CAN High and Low with the engine management module installed , a reading off 120 ohms is normal. However, to completely analyze the buss all modules should be temporally disconnected when testing for shorts between the CAN High and Low while also making sure that all modules and the scan tool are disconnected from the buss. Make certain to reconnect the BCM after testing, it is necessary for proper vehicle powermoding. The scan tool can not communicate directly with the CAN serial data circuit. It must use a serial data gateway module (SDGM), on this vehicle the SDGM is the ECM. A malfunction of the Keyword serial data circuit will emulate a malfunction on the CAN serial data circuit.

The engine will not start when there is a total malfunction of the CAN serial data circuits while the engine is not running. The following conditions may cause a total loss of CAN data communication:

•	A short between CAN High and CAN Low circuits

•	Any of the CAN serial data circuits shorted to ground or voltage

•	Any of the Keyword serial data circuits shorted to ground or voltage

•	A module internal malfunction that causes a short to voltage or ground on the CAN circuits

Test Description

The numbers below refer to the step numbers on the diagnostic table.

A partial malfunction in the CAN serial data circuits uses a different procedure from a total malfunction of the CAN data circuits.

Data link connector terminal 7 provides the connection to the Keyword serial data high circuit .

The communication malfunction may have prevented diagnosis of the customer complaint.

Step

Action

Yes

Schematic Reference: Data Link Connector Schematics

Connector End View Reference: Master Electrical Component List in Wiring Systems

Did you perform the Diagnostic System Check - Vehicle?

Go to Step 2

Go to Control Module References in Body Control System for the applicable diagnostic system check

Turn ON the ignition, with the engine OFF.
Perform the Vehicle DTC Information function on the scan tool, under Computer/Integrating Systems.

Does the scan tool communicate with any module on the CAN serial data circuits?

Go to Step 3

Go to Step 8

Did you record any DTCs in the range of U0100 to U0299?

Go to DTC U0100-U0299

Go to Step 4

Did you record any DTCs U2102 or U22103?

Go to DTC U2102 or U2103

Go to Step 5

Did you record any DTCs in the range of U2105 to U2108?

Go to DTC U2105-U2108

Go to Step 6

Did you record DTC U2104?

Go to DTC U2104

Go to Step 7

Did you record DTC U2100?

Go to DTC U2100

Go to Step 20

Important:: Turn ON the ignition, with the engine OFF, when testing for a short to voltage. Use the DMM MIN/MAX function to capture intermittent conditions.

Test the CAN serial data circuits for:

•	An intermittent short to ground

•	An intermittent short to voltage

•	An intermittent short between them

Refer to the following in Wiring Systems:

•	Testing for Intermittent Conditions and Poor Connections

•	Circuit Testing

•	Connector Repairs

•	Wiring Repairs

Did you find and correct the condition?

Go to Step 19

Go to Step 9

Test the following circuits of the body control module (BCM) for an open or short to ground:

•	The battery positive voltage input circuits

•	The battery positive voltage output circuits

•	The ignition mode switch input circuits

•	The switched battery positive voltage circuits

Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 19

Go to Step 10

Test the ground circuits of the BCM, ECM, EBCM, and TCM for an open. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 19

Go to Step 11

Turn OFF the ignition.
Disconnect the scan tool from the data link connector (DLC).
Inspect for poor a connection at the DLC terminal 7. . Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 19

Go to Step 12

Disconnect the farthest module from the ECM that is connected to CAN serial data circuits. Refer to Data Link Connector Schematics .
Install the scan tool.
Turn ON the ignition, with the engine OFF.
Attempt to communicate with the ECM.

Does the scan tool communicate with the ECM?

Go to Step 17

Go to Step 13

Turn OFF the ignition.
One at a time start disconnecting modules from the CAN serial data circuit, each time try to communicate with the ECM using the net two procedures below. Stop removing modules from the circuit if you establish communications. Refer to Data Link Connector Schematics .
Turn ON the ignition, with the engine OFF.
Attempt to communicate with the ECM.

Does the scan tool communicate with the ECM?

Go to Step 15

Go to Step 14

Important: There are two 120 ohms terminating resistors that connect between the High and Low CAN buss. Refer to Diagnostic Aids.

Test the CAN High and Low serial data circuits between the last disconnected modules for:

•	A short to ground

•	A short to battery

•	A short between CAN High and CAN Low--Refer to Diagnostic Aids.

Did you find and correct the condition?

Go to Step 19

Go to Step 15

Is the ECM the last module still connected to CAN data circuits?

Go to Step 16

Go to Step 13

Turn OFF the ignition.
Disconnect the ECM.
Disconnect the TCM.
Test the CAN serial data circuits between ECM and the previous disconnected module. for:

•	Short to ground

•	Short to battery

•	Short between CAN High and CAN Low--Refer to Diagnostic Aids.

•

An open

Test the Keyword serial data circuit between ECM and DLC

•	Short to ground

•	Short to battery

•

An open

Did you find and correct the condition?

Go to Step 19

Go to Step 17

Inspect for poor connections at the CAN serial data circuits of the last disconnected module and Keyword serial data circuits of the DLC, TCM and ECM.. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 19

Go to Step 18

Important: Perform the module setup procedure if required.

Replace the last disconnected module. Refer to Control Module References in Body Control System for the appropriate repair instructions.

Did you complete the replacement?

Go to Step 19

Reconnect all of the disconnected modules.
Install a scan tool.
Turn ON the ignition, with the engine OFF.
Wait for 10 seconds.

The scan tool may require a power up reset before communication will occur due to a short on the CAN serial data circuits. Turn OFF or disconnect the scan tool prior to performing this test.

Select the Display DTCs function for each module.
Record all of the displayed DTCs and the DTC status.

Did you record any DTCs which begin with a "U" and with a current status?

Go to Diagnostic Starting Point - Data Link Communications

Go to Step 18

Did you record any DTCs which do not begin with a "U"?

Go to Diagnostic Starting Point - Body Control Systemin Body Control System

Go to Step 21

Did you diagnose all of the DTCs?

Go to Step 22

Go to Step 20

Use the scan tool in order to clear the DTCs.

Did you complete the action?

System OK