Testing Procedure

Perform DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS in SELF-DIAGNOSTICS - ASCENDER 4.2L article. Go to next step.
Turn ignition on, with engine off. With a scan tool, observe the DTC information. Does the scan tool display DTCs P0107, P0601, P0602, P0604, P0606, P0607, P1220, P1221, P1271, P1514, P1621, P1631, P1635, P1639, P1680, P1681, or P1683? If any of these DTC's are present, see DIAGNOSTIC TROUBLE CODE DEFINITIONS in SELF-DIAGNOSTICS - ASCENDER 4.2L article. If none of the listed DTCs are present, go to next step.
Monitor the Ignition 1 signal voltage parameter with a scan tool. If the Ignition 1 signal voltage has battery voltage go to next step. If there is no battery voltage, go to step 10 .
Command the fuel pump ON with a scan tool. If the fuel pump turns on, go to next step. If the fuel pump does not turn on, see FUEL SYSTEMS in SYSTEM & COMPONENT TESTING article.
Turn ignition off. Remove an ignition coil. Install the Spark Tester (J 26792) to the coil boot. Attempt to start the engine. If the Spark Tester sparks go to the next step. If the Spark Tester does not spark, see IGNITION SYSTEMS in SYSTEM & COMPONENT TESTING article.
Turn ignition off. Disconnect the fuel injector harness multi-way connector. Probe a fuel injector control circuit, PCM side, with a test lamp connected to battery voltage. Crank the engine. If the test lamp flashes when cranking the engine, go to the next step. If the test lamp does not flash, see FUEL SYSTEMS in SYSTEM & COMPONENT TESTING article.
Turn ignition off. Install the Fuel Pressure Gauge (J 34730-1A). Turn ignition on, with engine off. Command the fuel pump ON with a scan tool. If the fuel pressure is within 48-52 psi (334-375 kPa) while the fuel pump is operating, go to the next step. If the fuel pressure is not within 48-52 psi (334-375 kPa), see FUEL SYSTEM DIAGNOSIS .
Disconnect the crankshaft position sensor. Attempt to start the engine. If the engine starts and continues to run, go to step 11 . If the engine does not start and continue running, go to next step.
Inspect for the following conditions:
- A collapsed air intake duct.
- A restricted air filter element.
- The spark plugs for being gas or coolant fouled. If the spark plugs are fouled, determine what caused the condition.
- An engine mechanical condition (worn timing chain, gears and low compression). See SYMPTOMS in appropriate ENGINE MECHANICAL article.
- A restricted exhaust system.
- The engine coolant temperature (ECT) sensor is NOT close to the actual engine temperature. See DTC P0117: ECT SENSOR CIRCUIT - LOW VOLTAGE or DTC P0118: ECT SENSOR CIRCUIT - HIGH VOLTAGE in SELF-DIAGNOSTICS - ASCENDER 4.2L article.
- Compare MAP/BARO parameters to another vehicle. The parameters should be close in value. See DTC P0105: MAP SENSOR CIRCUIT - INSUFFICIENT in SELF-DIAGNOSTICS - ASCENDER 4.2L article.
- The TP sensor for being stuck in range. See DTC P1221: THROTTLE POSITION SENSORS 1 & 2 CORRELATION in SELF-DIAGNOSTICS - ASCENDER 4.2L article.
When the check is complete go to step 12 .
Repair the ignition 1 signal voltage circuit for an open of a short to ground. See ENGINE PERFORMANCE in appropriate SYSTEM WIRING DIAGRAMS article in ELECTRICAL. Replace the fuse if necessary. When repair is complete, go to next step.
Replace the CKP sensor. See CRANKSHAFT POSITION SENSOR in REMOVAL & INSTALLATION article. Did you complete the replacement? If yes, go to the next step. If no, go to step 2 .
Clear the DTCs with a scan tool. Turn OFF the ignition for 30 seconds. Attempt to start the engine. If the engine starts and continues to run go to the next step. If the engine does not start and continue to run, go to step 2 .
Allow the engine to reach operating temperature. Observe the DTC information with a scan tool. If there are any DTCs that have not been diagnosed, go to DIAGNOSTIC TROUBLE CODE DEFINITIONS in SELF-DIAGNOSTICS - ASCENDER 4.2L article. If there are no DTCs system is okay.