Engine Cranks, But Will Not Run

Diagnostic Chart:

Wiring Diagram:

CIRCUIT DESCRIPTION

This engine is equipped with a distributorless ignition system called the Electronic Ignition (EI) system. The primary circuit of the EI system consists of two separate ignition coils, an electronic Ignition Control Module (ICM) and Crankshaft Position (CKP) sensor as well as the related connecting wires and the ignition control portion of the PCM. Each secondary circuit consists of the secondary winding of the coil, two connecting metal strips are molded into the coil housing, the spark plug boot/connector assemblies and spark plugs.

DIAGNOSTIC AIDS

A small amount of resistance in the battery positive voltage circuit to the PCM may cause a no start with a functioning Malfunction Indicator Lamp (MIL). Check the battery positive voltage circuit for excessive resistance or corrosion.

^ Check the Throttle Position (TP) sensor for binding or sticking or for being intermittently shorted or open.

^ If the THEFT SYSTEM telltale is flashing on the Instrument Panel Cluster (IPC), the theft deterrent system has been activated, refer to the DTC P1629 Theft Deterrent Crank Signal Malfunction for further diagnosis.
P1629

^ Check for water or foreign material in the fuel system.

^ Check for a basic engine problem (low compression).

^ Verify that only resistor spark plugs are used.

^ A scan tool can be used to energize the fuel pump ON to check the fuel pump operation and for ignition voltage at the fuel injector harness.

TEST DESCRIPTION

Number(s) below refer to the step number(s) on the Diagnostic Table.

1. The Powertrain OBD System Check prompts the technician to complete some basic checks and store the freeze frame and failure records data on the scan tool if applicable. This creates an electronic copy of the data taken when the malfunction occurred. The information is then stored in the scan tool for later reference.

2. Diagnosis of the DTCs that may be set could lead to the cause of the Cranks But Will Not Run condition.

3. The PCM grounds will only cause a problem if all the grounds are not making a good connection. If a PCM ground problem is suspected, the most probable place to check is where all the grounds meet at the engine block.

7. Locate and repair any shorts that may have caused the fuse to open before replacing the fuse.

8. A TP sensor that reads too high may cause an incorrect fueling condition.

9. An engine that has not been started should display Engine Coolant Temperature (ECT) and Intake Air Temperature (IAT) temperatures that are relatively close to each other. During the warmer weather, the IAT readings maybe slightly higher than the ECT readings.

10. This step looks for a normal barometer reading and a change in Manifold Absolute Pressure (MAP) sensor values while cranking the engine. This step verifies the MAP sensor can detect the change in the manifold pressure that occurs while cranking the engine. Compare any questionable barometer readings with readings from another vehicle.

11. While cranking the engine, the CKP Activity (7X reference) should increment to 255, then rollover to 0.

12. If the scan tool loses serial data only while cranking the engine, then the ignition switch is not sending voltage to the PCM while in the crank position.

13. Check for possible voltage loss to the PCM including the ignition switch itself.

14. The ignition positive voltage should be available at the ignition feed terminal (L) of the ICM 11 pin harness electrical connector, and the ground terminal (K) should be a good ground.

17. The CKP sensor core is a magnet and should be magnetized.

18. The CKP sensor should output a Idle Air Control (IAC) voltage near 110-1300 mV as the crankshaft turns. It is possible to trigger the ICM with a voltage as low as 200 mV. If no voltage is produced, a poor CKP sensor electrical connection or a malfunctioning CKP sensor is indicated.

19. The test light connected to B+ simulates a reference signal to the PCM. A fuel injector test light can be installed and will blink for every other touch of the test light if the CKP Activity (7X reference) circuit, the PCM and the fuel injector driver circuits are all functioning properly.

23. If the test light illuminates while probing the CKP Activity (7X reference) circuit, then the CKP Activity (7X reference) circuit is shorted to ground. If the test light remains OFF and the CKP Activity Counter does not increment, then the CKP Activity (7X reference) circuit is open. If the CKP Activity Counter increment several counts, when the reference low (terminal H) is probed, then the CKP Activity (7X reference) is shorted to voltage.

25. Replacement PCMs must be reprogrammed and the crankshaft position system variation learn procedure must be performed. Refer to the latest Techline information for PCM programming and the CKP System Variation Learn Procedure for the Crankshaft Position System Variation Procedure.

26. Battery voltage should be available at the fuel injector ignition feed circuit whenever the fuel pump power feed circuit is switched ON and when the PCM is receiving ignition pulses, during engine cranking or when running. The ignition switch must be turned OFF for at least 10 seconds to assure that the PCM powers down and will then switch the fuel pump back ON for 2-3 seconds when the ignition switch is turned back ON.

27. By installing the spark plug jumper leads and testing for spark on all 4 plug wire leads (one at a time), each ignition coil's ability to produced at least 25,000 volts is verified.

28. The fuel pump is turned ON by the PCM for 2-3 seconds after ignition switch is first turned ON. This step checks to see if the fuel pump and fuel pump relay are operating correctly and if the fuel pressure is within the proper range. Refer to the Fuel System Diagnosis for fuel pressure gauge installation procedure.
System Diagnosis - Fuel System

30. The ignition voltage is supplied to the fuel injectors and fuel pump for the first two seconds when the ignition switch is turned ON and continuously when the engine is cranked. If the fuel pump runs but the fuel injector test light did not blink, then the fuel injector ignition feed circuit is open between the fuel injector and the splice from the ignition feed circuit.

32. This step verifies that the PCM is sending a signal to the Ignition Control Module (ICM) to fire the ignition coils. If the test light blinks, then the signal is OK to this point and the no spark condition lies in the ignition coil electrical harness or the ignition coil that did not produce spark.

33. The ignition coil electrical harness can easily be checked by performing the previous step with the ignition coil electrical harness connected to the ICM. Check for a voltage and ground signal to the ignition coils at the coil electrical connector.