Diagnostic Instructions
Circuit/System Description
This Engine Cranks but Does Not Run diagnostic is an organized approach to identify a condition which causes the engine to crank but not start. This diagnostic directs the technician to the appropriate system diagnosis.
Diagnostic Aids
Inspect for any of the following conditions:
• | The engine control module (ECM) uses the camshaft position (CMP) sensors to determine engine speed and position when there is a crankshaft position (CKP) sensor condition. |
• | The engine will operate with a CKP sensor condition only if the ECM has stored the learned reference position of the camshafts in memory. With a CKP sensor condition in the signal circuit, the engine will go into a limp home mode after a restart.
The ECM then calculates engine speed from one of the CMP sensors. |
• | The fuel pump flow control module (FPCM) controls and monitors the operation of the in-tank fuel pump. If the FPCM detects a fault, a DTC sets in the FPCM. The FPCM will then send a serial data message to the engine control module (ECM) requesting
the illumination of the malfunction indicator lamp (MIL). |
• | Insufficient fuel can cause a no start condition. Thoroughly inspect the fuel delivery system for sufficient fuel volume to the fuel injectors. Inspect the fuel supply components for partial blockage or restrictions. |
• | Fuel injectors with partially blocked and restricted nozzles, or a malfunctioning solenoid, can cause a no start condition. Refer to
Fuel Injector Solenoid Coil Test. |
• | There may be fuel spray at the fuel injectors and the indicated fuel pressure may be correct, yet there may not be enough fuel to start the engine. If the fuel injectors and the injector circuit are OK, and fuel spray is detected, the fuel injector
ON time may be inadequate. If the engine control module (ECM) receives incorrect inputs from the various information sensors, the fuel delivered by the fuel injectors may be inadequate to start the engine. Check all the engine data parameters with a scan tool
and compare the values indicated with the expected values or the values from a known good vehicle. |
• | Inspect the engine for good secure electrical grounds. |
• | Water or foreign material in the fuel can cause a no start or engine will not stay running condition. During freezing weather water can freeze inside the fuel system. The engine may start after 30 minutes in a heated repair shop. The malfunction
may not recur until parked overnight in freezing temperatures. Extreme weather conditions can cause contaminated fuel to prevent the vehicle from starting. |
• | A vehicle that starts and runs after being brought to the repair shop for a no start condition, may have an ignition system that is susceptible to moisture. Spray water on the ignition system components and the wiring in order to check for an engine
starting or will not stay running concern. |
Reference Information
Schematic Reference
Engine Controls Schematics
Electrical Information Reference
Scan Tool Reference
Control Module References for scan tool information
Special Tools
• | CH 48027 Digital Pressure Gage
|
Circuit/System Verification
Note: This diagnostic assumes the following:
• | There is adequate fuel in the fuel tank. |
- Crank or start the engine. Observe the DTC information with a scan tool. Verify that DTCs P0116, P0118, P0119, P0335, P0336, P0338, P0351-P0356, P0601, P0602, P0604, P0606, P062B, P069E, P167D, P1629, P1631, P1632, P2105 or U0109 does not set.
- Ignition ON, observe the Theft Deterrent parameter with a scan tool. The parameter should display Disabled.
- Test the ignition system for spark. Refer to
Electronic Ignition (EI) System Diagnosis.
- Ignition ON, command the in-tank fuel pump ON with a scan tool. You should hear the fuel pump turn ON.
- Ignition OFF, install the
CH-48027 Gage
. Refer to
Fuel Pressure Gage Installation and Removal.
- Ignition ON, command an increase in the fuel line pressure with a scan tool. The fuel line pressure should increase to greater than 410 kPa (60 psi) as commanded.
- Verify that the following conditions do not exist:
• | Disconnect the MAF sensor. The engine control module (ECM) will ignore the MAF sensor and default to the calculated air flow. |
• | Collapsed air intake duct to the throttle body |
• | Restricted air filter element |
⇒ | If you find any of the above conditions, repair as necessary. |
Repair Instructions
Perform the
Diagnostic Repair Verification after completing the diagnostic procedure.