Diagnostic Aids

Inspect for any of the conditions listed below:

• An open Ignition/Injector fuse may prevent the engine from starting and/or continuing to run. This engine application uses 2 fuses, one for each cylinder bank, to supply ignition 1 voltage to the ignition module/coil assemblies and also to the fuel injectors. If either fuse is open, ignition spark and fuel injection spray will be lost for the entire cylinder bank affected.
• Fuel injectors with partially blocked and restricted nozzles, or a malfunctioning solenoid, can cause a no start condition.
• There may be fuel spray at the fuel injectors and the indicated fuel pressure may be correct, yet there may not be enough fuel to start the engine. If the fuel injectors and the injector circuit are OK and fuel spray is detected, the fuel injector ON time may be inadequate. If the engine control module (ECM) receives incorrect inputs from the various information sensors, the fuel delivered by the fuel injectors may be inadequate to start the engine. Observe all the engine data parameters with a scan tool and compare the values indicated with the expected values or the values from a known good vehicle.
• Observe the Engine Speed parameter while cranking the engine. The scan tool should indicate a steady 200 - 300 RPM while cranking. If erratic values such as sudden spikes in the engine speed are displayed, the engine reference signal is not stable enough for the engine to start and run properly.
• Inspect the engine for good secure electrical grounds.
• If the engine almost starts and then stalls, inspect for an open in the ground circuits of the crankshaft position sensor and the camshaft position sensor.
• An engine that starts and runs after being brought to the repair shop for a no start condition may have an ignition system that is susceptible to moisture. Spray water on the ignition system components and the wiring in order to verify for an engine starting or will not stay running concern.
• When disconnecting electrical connectors or removing fuses and relays, always inspect electrical terminals for corrosion and for adequate terminal tension.