Scan Tool Does Not Communicate with Class 2 Device. Saturn ION 2004

For 1990-2009 cars only

Makes 🢒 Saturn 🢒 2004 🢒 ION 🢒 Engine 🢒 Engine Electrical 🢒 Scan Tool Does Not Communicate with Class 2 Device

Circuit Description

Modules connected to the class 2 serial data circuit monitor for serial data communications during normal vehicle operation. Operating information and commands are exchanged among the modules. Connecting a scan tool to the DLC allows communication with the modules for diagnostic purposes.

Diagnostic Aids

The engine will not start when there is a total loss of class 2 serial data communication while the ignition is OFF. The serial data bus can not be used to analyze a malfunction on the class 2 serial data bus. The following conditions will cause a total loss of class 2 serial data communication:

•	A class 2 serial data circuit shorted to ground. A history U1300 will set in all modules. Refer to DTC U1300, U1301, or U1305 .

•	A class 2 serial data circuit shorted to voltage. A history U1301 will set in all modules. Refer to DTC U1300, U1301, or U1305 .

•	An internal condition within a module or connector on the class 2 serial data circuit, that causes a short to voltage or ground to the class 2 serial data circuit.

Test Description

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

A partial loss of communication in the class 2 serial data circuit uses a different procedure than a total loss of communication of the class 2 serial data circuit.

The following DTCs may be retrieved with a history status. These DTCs are not the cause of the present condition.

A State of Health DTC with a history status may be present along with a U1000 or U1255 with a current status. This indicates that the malfunction occurred when the ignition was on.

Normal class 2 serial data communication cannot take place until the power mode master (PMM) module sends the appropriate power mode message. If the PMM does not send a wake-up message, other modules on the class 2 serial data circuit may not communicate.

This step will isolate a wiring problem or a module malfunction.

An open circuit at this point will cause a loss of communication with the vehicle.

This step analyzes the specific branch circuit for a malfunction.

If there are no current DTCs that begin with the letter "U", the communication concern has been repaired.

The communication concern 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

Install a scan tool.

Does the scan tool power up?

Go to Step 2

Go to Scan Tool Does Not Power Up

Turn ON the ignition, with the engine OFF.
Attempt to communicate with each module on the class 2 serial data circuit. If using a Tech 2, obtain this information using the Class 2 Message Monitor feature.

Does the scan tool communicate with any module on the class 2 serial data circuit?

Go to Step 3

Go to Step 8

Select the Display DTCs function for each module. If using a Tech 2, use the Class 2 DTC Check feature in order to determine which modules do have DTCs set.
Record all of the displayed DTCs, the DTC status and the module which set the DTC.

Did you record any DTCs in the range of U1000 to U1305?

Go to Step 4

Go to Step 7

Are history DTCs U1300, U1301 or U1305 retrieved from any module?

Go to Step 5

Go to Step 6

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

Test the class 2 serial data circuit for an intermittent short to ground or an intermittent short to voltage. 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 18

Go to Step 6

Are U1000 or U1255 the only DTCs displayed in the previously specified range?

Go to DTC U1000 and U1255

Go to DTC U1001-U1254

Diagnose the non communicating module by using the DTC U1001 - U1254 Lost Communications with XXX procedure for the module which is not communicating. The DTC U1001 - U1254 Lost Communications with XXX procedure will determine which module is not communicating. Refer to DTC U1001-U1254 .

Did you complete the action?

Go to Control Module References in Body Control System for the applicable Diagnostic System Check

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

Did you find and correct the condition?

Go to Control Module References in Body Control System for the applicable Diagnostic System Check

Go to Step 9

Test the ground circuits of the DLC for an open or high resistance. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Control Module References in Body Control System for the applicable Diagnostic System Check

Go to Step 10

Isolate the power mode master (PMM) module from all other modules on the class 2 serial data circuit by backing out only the class 2 serial data terminals from the PMM harness connectors, except for the one class 2 serial data circuit that is routed to the DLC, pin 2. To identify which module is the PMM refer to Body Control System Description and Operation in Body Control System, also refer to Data Link Connector Schematics for the circuit ID.
Connect all of the PMM harness connectors with the extracted class 2 serial data circuit terminals.
Turn the ignition ON, with the engine OFF.
Attempt to communicate with the PMM.

Does the scan tool communicate with the PMM?

Go to Step 12

Go to Step 11

Test the class 2 serial data circuits between the DLC and the PMM for the following conditions. Turn ON the ignition when testing for a short to voltage:

•	High resistance

•

Open

•	Short to ground

•	Short to voltage

Test the following circuits of the PMM for an open or high resistance:

•	The battery positive voltage input circuits

•	The battery positive voltage output circuits

•	The ignition voltage input circuits

•	The ignition voltage output circuits

•	The switched battery positive voltage supply circuits

•	The ground circuits

Refer to Circuit Testing and Wiring Repairs in Wiring Systems

Did you find and correct the condition?

Go to Step 18

Go to Step Step 17

Perform the following for each class 2 serial data branch circuit, in order to determine if the concern is located within the class 2 serial data branch circuits or the modules connected to the class 2 bus:

Turn the ignition OFF.
One at a time, replace each terminal in the PMM harness connectors.
Turn the ignition ON, with the engine OFF.
Attempt to communicate with any module connected to the class 2 serial data branch circuit after reinstalling it's class 2 serial data terminal.
Record which branch of the class 2 serial data circuit causes a loss of communication if one occurs in the above items.

Does the scan tool communicate with all modules connected to the class 2 serial data circuit after all the branch circuits have been reconnected?

Go to Step 13

Go to Step 14

Inspect for poor connections and terminal tension at the harness connector of the PMM harness connector that contains the discreet class 2 serial data circuit for the DLC.

Did you complete the action?

Go to Step 18

Turn the ignition OFF.
Using the record made in step 12, identify each module on that branch of the class 2 serial data circuit and disconnect there harness connectors containing the class 2 serial data circuits.
Using the record made in step 12 again, test the branch circuits that caused a No Com with class 2 for the following. Turn the ignition ON when testing for a short to voltage:

•	Short to ground

•	Short to voltage

Did you find and correct the problem?

Go to Step 18

Go to Step 15

The concern is a malfunctioning module on the class 2 serial data branch circuit recorded in step 12.

Turn the ignition OFF.
One at a time, starting with the first module on the malfunctioning class 2 serial data branch circuit closest to the PMM, start attaching modules back onto that branch circuit.
Turn the ignition ON, with the engine OFF.
Attempt to communicate with the reinstalled modules connected to the malfunctioning branch.
Repeat items 1 through 4 attempting to lose communication. If communication is lost, record the last module reconnected proceed down the table and discontinue the repeating of items 1 through 4.

Does the scan tool communicate with all the modules connected to the class 2 serial data circuit?

Go to Step 18

Go to Step 1

Inspect for poor connections and terminal tension at the harness connector of the reconnected module that causes a loss of communication. 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 18

Go to Step 17

Important: Perform the module setup procedure if required.

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

Did you complete the replacement?

Go to Step 18

Connect all of the modules.
Connect all the connectors.
Install a scan tool.
Turn the ignition ON leaving the engine OFF.

Important: The scan tool may require a power up reset before communication will occur due to a short on the class 2 serial data circuit. Turn off or disconnect the scan tool before you display DTCs.

Wait for 10 seconds.
Select the display DTCs function for each module. If using a Tech 2, use the Class 2 DTC Check feature in order to determine which modules do have DTCs set.
Record all of the displayed DTCs and the DTC status.

Did your record any DTCs which begin with a letter U and with a current status?

Go to Step 20

Go to Step 19

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

Go to Step 20

Go to Step 22

Diagnose the DTCs as directed by the diagnostic procedures for the particular module or concern.

Did you complete the action?

Go to Step 21

Did you diagnose all of the DTCs?

Go to Step 22

Go to Step 20

Clear the DTCs using the scan tool.

Did you complete the action?

Go to Control Module References in Body Control System for the applicable Diagnostic System Check