Engine Cranks But Does Not Run. Generic Unit Repair 2003

For 1990-2009 cars only

Makes 🢒 Generic 🢒 2003 🢒 Unit Repair 🢒 Engine 🢒 Engine Controls - 4.8L, 5.3L, and 6.0L 🢒 Engine Cranks But Does Not Run

Description

The Engine Cranks but Does Not Run diagnostic table is an organized approach to identifying a condition that causes an engine to not start. The diagnostic table directs the service technician to the appropriate system diagnosis. The diagnostic table assumes the following conditions are met:

•	The battery is completely charged.

•	The engine cranking speed is acceptable.

•	There is adequate fuel in the fuel tank.

Diagnostic Aids

Inspect for the following conditions:

•

The mass air flow (MAF) is compared to a calculated MAF based upon the manifold absolute pressure (MAP), the throttle position (TP), and the engine RPM. A skewed or unresponsive MAP sensor at key ON will cause the predicted air flow value to be inaccurate. Compare the MAP and TP readings to that of a known good vehicle.

•	Inspect for a faulty engine coolant temperature (ECT) sensor. Use a scan tool in order to compare the ECT with the intake air temperature (IAT) on a completely cooled engine. The ECT should be within 3°C (5°F) of the IAT.

•	For an intermittent condition, refer to Intermittent Conditions .

Step

Action

Values

Yes

Schematic Reference: Engine Controls Schematics

Did you perform the Diagnostic System Check-Engine Controls?

Go to Step 2

Go to Diagnostic System Check - Engine Controls

Crank the engine for the specified amount of time.

Does the scan tool display any DTCs that failed this ignition?

15 seconds

Go to Diagnostic Trouble Code (DTC) List

Go to Step 3

Does the scan tool display any body control module (BCM) vehicle theft deterrent (VTD) DTCs?

Go to DTC List in Theft Deterrent

Go to Step 4

Observe the engine speed parameter with a scan tool, while cranking the engine.

Is the engine RPM indicated on the scan tool?

Go to Step 5

Go to Electronic Ignition (EI) System Diagnosis

Turn ON the ignition, with the engine OFF.
Probe both sides of the PCM 1 fuse located in the underhood electrical center with a test lamp connected to a good ground.

Does the test lamp illuminate on at least on side of the fuse?

Go to Step 6

Go to Ignition Relay Diagnosis

Monitor the ignition 1 signal parameter with a scan tool.

Is the ignition 1 signal parameter at the specified value?

B+

Go to Step 7

Go to Step 10

Command the fuel pump ON with a scan tool.

Does the fuel pump operate?

Go to Step 8

Go to Fuel Pump Electrical Circuit Diagnosis

Turn OFF the ignition.
Install a fuel pressure gauge. Refer to Fuel System Diagnosis .

Important: The fuel pump operates for about 2 seconds when the ignition is turned ON. The fuel pressure must be observed when the fuel pump is operating.

Turn ON the ignition, with the engine OFF.
Observe the fuel pressure while the fuel pump is operating.

Is the fuel pressure within the specified range?

385-425 kPa (55-62 psi)

Go to Step 9

Go to Fuel System Diagnosis

Inspect for the following conditions:

•	The engine coolant temperature (ECT) sensor is not close to the actual engine temperature. Refer to DTC P0125 .

•	The duct work between the MAF sensor and the throttle body for air leaks

•	A restricted exhaust system.

•

A malfunctioning MAF sensor may cause a no start or a stall after a start. If you suspect this, disconnect the MAF sensor. The PCM will default to the speed density in order to calculate the engine load and the intake air flow. If disconnecting the MAF sensor corrects the condition and the connections are OK. Refer to DTC P0102 .

•	The spark plugs for being gas fouled--Refer to Spark Plug Inspection .

•	An engine mechanical failure that causes an engine not to start such as timing chain, low compression--Refer to Engine Compression Test in Engine Mechanical 4.8L, 5.3L, 6.0L.

•	Compare the MAP/BARO parameters to another vehicle. The parameter values should be close to each other.

Did you complete the action?

Go to Step 13

Test the ignition 1 signal voltage circuit for an open or for a short to ground. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.
Replace the fuse if necessary.

Did you find and correct the condition?

Go to Step 13

Go to Step 11

Inspect for poor connections at the harness connector of the PCM. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 13

Go to Step 12

Replace the PCM. Refer to Powertrain Control Module Replacement .

Did you complete the replacement?

Go to Step 13