Diagnosis & Repair
- Check valve timing. Rotate crankshaft clockwise until No. 1 piston is at TDC of compression stroke. The No. 1 piston is front cylinder on left side when viewed from rear of engine. Ensure timing mark on crankshaft pulley aligns with "0" mark on No. 1 timing cover.
- Ensure timing marks on camshaft sprockets align with timing marks on timing belt rear plates. If timing marks do not align, timing belt is loose or timing belt has damaged teeth. If valve timing is okay, replace ECM and retest. If valve timing is incorrect, adjust belt tension or replace timing belt. See the 4.0L article in the ENGINE MECHANICAL section.