Engine Cranks But Does Not Run
Engine Cranks but Does Not Run
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 2 separate ignition coils, an electronic ignition control module (ICM) and a crankshaft position (CKP) sensor as well as the related connecting wires and the ignition control (IC) portion of the PCM. Each secondary circuit consists of the secondary winding of the coil, spark plug wires, and the spark plugs.
IMPORTANT: The camshaft position (CMP) sensor is only used for misfire detection and is not part of the ignition system.
Diagnostic Aids
An intermittent DTC can also be the result of a defective reluctor wheel. Remove the crankshaft sensor and inspect the reluctor wheel through the crankshaft sensor mount hole. Check the porosity and the condition of the reluctor wheel.
Perform the Fuel Injector Balance Test.
Steps 1 - 2:
Steps 3 - 8:
Steps 9 - 13:
Steps 14 - 16:
Steps 17 - 21:
Steps 22 - 26:
Steps 27 - 31:
Steps 32 - 36:
Steps 37 - 39:
Test Description
The numbers below refer to the step numbers 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.
6. Locate and repair any shorts that may have caused the fuse to open before replacing the fuse.
7. A TP sensor that reads too high may cause an incorrect fueling condition.
8. An engine that has not been started should display ECT and IAT temperatures that are relatively close to each other. During the warmer weather, the IAT readings maybe slightly higher than the ECT readings.
9. 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.
10. This step looks for a normal barometer reading and a change in 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.
16. By testing for spark on all 4 plug wire leads using a spark tester, each ignition coils ability to produced at least 25,000 volts is verified.
19. The CKP sensor should output a voltage near 1100 - 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 malfunctioning CKP sensor is indicated.
22. The test lamp connected to B+ simulates a reference signal to the PCM. An fuel injector test lamp can be installed and will blink for every other touch of the test lamp if the CKP Activity (7X reference) circuit, the PCM and the fuel injector driver are all functioning properly.
32. The replacement PCM must be programmed and the crankshaft position system variation procedure must be performed. Refer to the latest Techline procedures for PCM programming.
34. The fuel pump is turned ON by the PCM for 2 - 3 seconds after the ignition 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 the fuel pressure gage installation procedure.
35. Battery voltage should be available at the fuel injector ignition positive voltage circuit whenever the fuel pump power supply circuit is switched ON and when the PCM is receiving ignition pulses, during engine cranking or when the engine is running. The ignition 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 is turned back ON.