Circuit/System Testing

WARNING: This page is about a different car, the 2010 GMC Sierra and 2010 Chevrolet Silverado. However, it is still accessible from the selected car via links, so may be relevant.

Crank the engine while observing the scan tool Vehicle DTC Information.
- If any of the following DTCs are set, diagnose these first: DTC P0117, P0118, P0122, P0123, P0201-P0208, P0222, P0223, P0335, P0336, P0351-P0358, P0513, P0562, P0563, P0601-P0604, P0606, P0607, P062F, P0633, P0685, P0690, P1516, P1631, P1682, or P2610. Refer to Diagnostic Trouble Code (DTC) List - Vehicle .
With the ignition ON and the engine OFF, test the fuses that are supplied ignition 1 voltage by the powertrain relay. The test lamp should illuminate ON for each test point of the fuses.
- If the test lamp does not illuminate on, for at least one test point of each fuse, refer to DTC P0685, P0689, or P0690 .
Crank the engine while observing the scan tool engine speed parameter.
- If engine RPM is not indicated, refer to DTC P0335 or DTC P0336 .
Install a spark plug tester onto one ignition module/coil assembly, on each bank of the engine.

NOTE: An erratic or weak spark is considered a no spark condition.

Crank the engine while observing both spark plug testers. Both spark plug testers should spark.
- If spark is not observed, is inconsistent, or weak on either spark plug tester, refer to Electronic Ignition System Diagnosis .
With the ignition ON and the engine OFF, command the fuel pump ON and OFF with the scan tool. The fuel pump should energize when commanded ON, and de-energize when commanded OFF.
- If the fuel pump does not turn ON and OFF, refer to Fuel System Diagnosis (Without FPCM) or Fuel System Diagnosis (FPCM) .
Turn OFF the ignition.
Install the J 34730-1A Fuel Pressure Gauge. With the ignition ON and the engine OFF, command the fuel pump ON several times with the scan tool. Refer to Fuel System Diagnosis for the fuel pressure specification.
Inspect for the following conditions:
- Compare the actual engine coolant temperature to the ECT parameter
- Filter and air intake system for restrictions and obstructions
- Test the fuel for contamination-Refer to Alcohol/Contaminants-in-Fuel Diagnosis (Without Special Tool) or Alcohol/Contaminants-in-Fuel Diagnosis (Special Tool) .
- Inspect the spark plugs-Refer to Spark Plug Inspection .
- Test the exhaust system for restrictions-Refer to Restricted Exhaust .
- Engine mechanical conditions, such as worn timing chain, sprocket gears, low compression, etc-Refer to Symptoms - Engine Mechanical .