Circuit/System Testing

WARNING: This page is about a different variant/trim than selected.

Crank the engine while observing the scan tool Vehicle DTC Information.
- If any of the following DTCs are set, diagnose these DTCs first: DTC P0117, P0118, P0122, P0123, P0201-P0208, P0222, P0223, P0335, P0336, P0351-P0358, P0562, P0563, P0601-P0604, P0607, P062F, P0633, P0685, P0690, 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 or P0690 .
Crank the engine while observing the scan tool engine speed parameter.
- If engine RPM is not indicated, refer to DTC P0335 .
Disconnect the B75B mass airflow (MAF) sensor. Attempt to start the engine. The ECM will ignore MAF sensor input, default to calculated airflow, and the engine should start and run if the MAF sensor is faulted.
- If the engine starts and runs, and the MAF sensor circuits test OK, replace the B75B MAF sensor.
Install a spark plug tester onto one T8 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 .
Turn OFF the ignition.
Install the J 34730-1A: Gauge Fuel Pressure Gauge. Refer to Fuel Pressure Gauge Installation and Removal . 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.
Verify the following conditions do not exist:
- Restricted air filter element or air intake system
- Spark plugs for being gas or coolant fouled-Refer to Spark Plug Inspection
- A skewed manifold absolute pressure (MAP) sensor-Refer to DTC P0106 .
- A skewed engine coolant temperature (ECT) sensor-Refer to DTC P0116 .
- Exhaust system restricted-Refer to Restricted Exhaust .
- Fuel contamination-Refer to Alcohol/Contaminants-in-Fuel Diagnosis (with Special Tool) or Alcohol/Contaminants-in-Fuel Diagnosis (without Special Tool) .
- Engine mechanical condition, for example, worn timing chain, sprocket gears, low compression, etc.-Refer to Symptoms - Engine Mechanical and Timing Chain, Crankshaft Sprocket, Camshaft Position Actuator, and Solenoid Valve Replacement .
- If any of the above conditions exist, repair as necessary.