Diagnostic Fault Information
Perform the
Diagnostic System Check - Vehicle
.
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
hard restart. The ECM then calculates engine speed from one of the CMP sensors. During
a limp home mode, the following additional DTCs may set and should be ignored: |
- | DTC P0324 Knock Sensor (KS) Module Performance |
- | DTC P1011 Intake Camshaft Position Actuator Park Position Bank 1 |
• | 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. |
• | 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 |
• | Check the crankshaft position (CKP) sensor engine reference signal with
a scan tool. Observe the Engine Speed parameter while cranking the engine. The scan
tool should indicate a steady 200-300 RPM while cranking. If erratic
values, such as sudden spikes in the engine speed are displayed, the engine reference
signal is not stable enough for the engine to start and run properly |
• | Inspect the engine for good secure electrical grounds |
• | If the engine almost starts and then stalls, check for an open in the
ground circuits of the CKP sensor and the camshaft position (CMP) sensor |
• | 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
.
Connector End View Reference
Component Connector End Views
.
Electrical Information Reference
DTC Type Reference
Diagnostic Trouble Code (DTC) Type Definitions
.
Scan Tool Reference
Control Module References
.
Special Tools Required
• |
AU-465
Fuel gauge
adapter hose. |
Circuit/System Verification
Important: This diagnostic assumes the following:
• | There is adequate fuel in the fuel tank. |
- Ignition ON, observe the DTC information with a scan tool. Verify that
DTCs P0685, P0686, P0687, P0689, or P0690 are not set.
- Crank the engine for 15 seconds. Observe the DTC information with
a scan tool. Verify that DTCs P0116, P0118, P0119, P0201-P0206, P0335, P0336,
P0337, P0338, P0351-P0356, P0601, P0602, P0604, P0606, P0627, P0628, P0629,
P1629, P1630, P1631, or P2105 do 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 fuel pump ON with a scan tool. You should hear
the fuel pump turn ON.
- Ignition OFF, install the
AU-338
and the
AU-465
. Refer to
Fuel Pressure Gage Installation and Removal
.
Important:
• | The fuel pump may need to be commanded ON a few times, in order to obtain
the highest possible fuel pressure |
• | Do NOT start the engine for this test. |
- Ignition ON, command the fuel pump ON with a scan tool. The fuel pressure should
be between 380-410 kPa (55-60 psi).
- If the fuel pressure is not within range, refer to
Fuel System Diagnosis
.
- 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
.