Possible Causes & Corrections

Check the following items:

• Check coolant level. Check cooling system thermostat for proper operation and application.
• Check for restricted airflow to radiator or restricted coolant flow through radiator.
• Check for loose water pump belt.
• Check Engine Coolant Temperature (ECT) sensor, reading should be within 5°F of ambient air temperature on a cold engine.
• Inspect the Fuel Rail Pressure (FRP) sensor. Use the scan tool to observe FRP with ignition on and engine off. FRP should be 1.1-1.4 MPa. If FRP is not within this range, check for high resistance in the low reference or 5-volt reference circuits or the sensor, or a faulty sensor.
• Inspect for an intermittent Crankshaft Position (CKP) sensor signal.
• Inspect CKP sensor reluctor wheel. Remove CKP sensor and attempt to move the reluctor wheel front to back or side to side with a probe. If there is any movement the reluctor wheel retaining bolts are loose.
• Check fuel injection pump and timing. See appropriate ON-VEHICLE ADJUSTMENTS article.
• Check injector nozzles. See appropriate SYSTEM & COMPONENT TESTING article.
• Inspect fuel delivery system. Check for no fuel to injection pump or air in fuel system. See BASIC FUEL SYSTEM CHECKS (DIESEL) in appropriate BASIC DIAGNOSTIC PROCEDURES article.
• Check for incorrect basic engine parts such as camshaft, cylinder heads and pistons.
• Check for excessive blow-by.