Skip to content
Tahoe / Yukon Service Manual

Engine Cranks Slowly

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. Reference Information Schematic Reference Starting and Charging Schematics Connector End View Reference Master Electrical Component List Description and Operation Starting System 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 Testing

  1. Ignition OFF, measure and record the C1 Battery voltage at the terminals.
  2. Verify the measured voltage is between 12.0–15.0 V. ⇒ If voltage is less than 12.0 V or greater than 15.0 V Refer to Battery Inspection/Test. ⇓ If voltage is between 12.0–15.0 V
  3. Test for less than 0.5 V between the positive battery terminal and positive terminal at the X50B Battery Distribution Engine Compartment Fuse Block with the Engine Cranking. ⇒ If 0.5 V or greater Replace the positive battery cable. ⇓ If less than 0.5 V
  4. Test for less than 0.5 V between the positive battery cable at the X50B Battery Distribution Engine Compartment Fuse Block and terminal 1 X2 or A X2 at the M64 Starter Motor with the with the Engine Cranking. ⇒ If 0.5 V or greater Replace the positive battery cable. ⇓ If less than 0.5 V
  5. Test for less than 0.5 V between the negative battery cable and the M64 Starter Motor case with the with the Engine Cranking. ⇒ If 0.5 V or greater Replace the negative battery cable. ⇓ If less than 0.5 V
  6. Remove the drive belts. Refer to: . Accessory Drive Primary Belt Replacement 3.0L (LM2) Accessory Drive Primary Belt Replacement 5.3L (L83, L84, L8B), 6.2L (L86 L87 LT1 LT2 LT4) Accessory Drive Auxiliary Belt Replacement 5.3L (L83, L84, L8B), 6.2L (L86 L87 LT1 LT2 LT4)
  7. Verify the engine cranks slowly when attempting to start the vehicle. ⇒ If the engine cranks at normal speed Inspect the engine and belt drive system for mechanical binding, seized generator etc. ⇓ If the engine cranks slowly
  8. Replace the M64 Starter Motor. Repair Instructions Perform the Diagnostic Repair Verification after completing the repair. Battery Positive and Negative Cable Strap Replacement Starter Solenoid Cable Replacement Engine Wiring Harness Junction Block Replacement Starter Replacement