Scan Tool Tech 2 Diagnostic Scan Tool

Important: Cranking speed is critical for a diesel engine to start, whether the engine is hot or cold. The only approved method of testing cranking speed is to use a Tech 2 Diagnostic Scan Tool.

1. Ensure that the vehicle's batteries are in good condition, and fully charged. Refer to Battery Not Operating Properly in Engine Electrical.
2. Remove the fuel solenoid fuse. Refer to Engine Controls Component Views (L57) or Engine Controls Component Views (L65) in Engine Controls.
3. Connect the Scan Tool Tech 2 Diagnostic Scan Tool.
4. Crank the engine for 2 to 4 seconds. This will allow the starter to reach it's maximum performance.
5. Observe the engine RPM reading on the Tech 2 Diagnostic Scan Tool. Refer to Engine Mechanical Specifications in Engine Mechanical. The actual cranking speed needed for starting will vary depending on the condition of the engine mechanical components (compression), and the condition of the fuel system components (fuel injection pump operating pressure, and fuel injection nozzles cracking pressure and spray pattern).
6. If the engine fails to meet the minimum specified cranking speed, repair or replace damaged or malfunctioning components and retest.
7. Disconnect the Tech 2 Diagnostic Scan Tool.
8. Install the fuel solenoid fuse.