NOTE: This test will confirm or deny proper operation of J1850 communication network or ISO 9141 communication link. Perform following procedure with ignition switch in RUN position.

Connect New Generation Star (NGS) scan tester to the Data Link Connector (DLC) and perform proper hook-up procedure. See EQUIPMENT HOOK-UP under COMMUNICATION NETWORK DIAGNOSTICS.
Turn ignition on. Rotate dial on scan tester to menu item DIAGNOSTIC DATA LINK and press trigger. A test will be performed on the J1850 network bus circuits No. 914 (Tan/Orange wire) and No. 915 (Pink/Light Blue wire) and the ISO 9141 communication link circuit No. 70 (Light Blue/White wire).
If scan tester displays CKT 914 (+) = SYSTEM PASSED and CKT 915 (-) = SYSTEM PASSED, the J1850 module communications network is okay. If scan tester displays CKT 70 = SYSTEM PASSED, ISO 9141 communication link is operating properly.
If scan tester does not display the above message (SYSTEM PASSED), proceed testing for J1850 module communication network failure or ISO 9141 communication link failure. See DIAGNOSTIC PROCEDURE SEQUENCE under COMMUNICATION NETWORK DIAGNOSTICS .

When to See a Mechanic

Stop DIY work and contact a certified mechanic immediately if any of the following apply:

• You smell fuel, burning insulation, or see smoke.

• Brakes feel soft, pull hard to one side, or make grinding noises.

• The engine overheats, stalls repeatedly, or misfires under load.

• You are missing required tools, torque specs, or safe lifting equipment.

• You are not confident in the next step or safety outcome.

Safety Warning

Data Link Diagnostics

Use the Manual With the Right Hardware

When to See a Mechanic

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