DTC P0300. Cadillac XLR 2005

For 1990-2009 cars only

Makes 🢒 Cadillac 🢒 2005 🢒 XLR 🢒 Engine 🢒 Engine Electrical 🢒 DTC P0300

System Description

The engine control module (ECM) uses information from the crankshaft position (CKP) sensor and the camshaft position (CMP) sensor in order to determine when an engine misfire is occurring. By monitoring variations in the crankshaft rotation speed for each cylinder, the ECM is able to detect individual misfire events. A misfire rate that is high enough can cause 3-way catalytic converter damage. The malfunction indicator lamp (MIL) will flash ON and OFF when the conditions for catalytic converter damage are present. DTCs P0301-P0308 correspond to cylinders 1-8. If the ECM is able to determine that a specific cylinder is misfiring, the DTC for that cylinder will set.

DTC Descriptor

This diagnostic procedure supports the following DTC:

DTC P0300 Engine Misfire Detected

Conditions for Running the DTC

•	DTCs P0102, P0103, P0315, P0335, P0336, P0365, P0366, or P0390 are not set.

•	The engine speed is between 500-6,496 RPM.

•	The engine load is more than 0 percent.

•	The torque management is not active.

•	The fuel level is more than 10.5 liters (3 gallons).

•	The antilock brake system (ABS) is not active.

•	The ECM is not receiving a rough road signal.

•	The ECM is not in fuel shut-off or decel mode.

•	The engine coolant temperature (ECT) is more than -7.5°C (+18.5°F).

•	DTC P0300 runs continuously once the above conditions are met.

Conditions for Setting the DTC

The ECM is detecting a crankshaft rotation speed variation indicating a misfire rate sufficient to cause emissions levels to exceed mandated standards.

Action Taken When the DTC Sets

•	The control module illuminates the malfunction indicator lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.

•

The control module records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the control module stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the control module records the operating conditions at the time of the failure. The control module writes the operating conditions to the Freeze Frame and updates the Failure Records.

Conditions for Clearing the MIL/DTC

•	The ECM turns OFF the MIL after 3 consecutive drive trips that the diagnostic runs and does not fail within the same conditions that the DTC last failed.

•	A History DTC clears after 40 consecutive warm-up cycles if no failures report by this diagnostic or any other emission related diagnostic.

•	The DTC can be cleared with a scan tool

Diagnostic Aids

•	Excessive vibration from sources other than the engine could cause DTC P0300 to set. The following are possible sources of vibration:

-	Thickness variation of the brake rotors--Refer to Symptoms - Hydraulic Brakes in Hydraulic Brakes.

-	The drive shaft not balanced--Refer to Vibration Analysis - Driveline in Vibration Diagnosis and Correction.

-	Worn or damaged accessory drive belt--Refer to Symptoms - Engine Mechanical in Engine Mechanical.

•	There may be more or less cylinders actually misfiring than indicated by the scan tool.

•	If there are multiple misfires on only one bank, inspect the fuel injector and ignition coil, power and ground circuits for that bank. Refer to Engine Controls Schematics .

Test Description

The number below refers to the step number on the diagnostic table.

If the actual CKP variation values are not within the learned values, the misfire counters may increment.

Step

Action

Values

Yes

Did you perform the Diagnostic System Check - Vehicle?

Go to Step 2

Go to Diagnostic System Check - Vehicle in Vehicle DTC Information

Important: You must perform the crankshaft position (CKP) system variation learn procedure before proceeding with this diagnostic table. Refer to Crankshaft Position System Variation Learn .

Start the engine.
Allow the engine to idle or operate within the conditions listed in the Freeze Frame/Failure Records.
Monitor all of the Misfire counters with the scan tool.

Are any of the Misfire counters incrementing?

Go to Step 3

Go to Diagnostic Aids

Are any other DTCs set?

Go to Diagnostic Trouble Code (DTC) List - Vehicle in Vehicle DTC Information

Go to Step 4

Can any abnormal engine noise be heard?

Go to Symptoms - Engine Mechanical in Engine Mechanical

Go to Step 5

Inspect the following components:

•	The vacuum hoses and seals for splits, restrictions, and improper connections

•	The throttle body and intake manifold for vacuum leaks

•	The exhaust gas recirculation (EGR) system components for vacuum leaks or excessive flow

•	The crankcase ventilation system for vacuum leaks--Refer to Crankcase Ventilation System Inspection/Diagnosis in Engine Mechanical.

•	The engine control module (ECM) grounds for corrosion and loose connections--Refer to Ground Distribution Schematics in Wiring Systems.

•	The exhaust system for restrictions--Refer to Restricted Exhaust in Engine Exhaust.

•	The fuel for contamination--Refer to Alcohol/Contaminants-in-Fuel Diagnosis .

Did you find and correct the condition?

Go to Step 16

Go to Step 6

Turn OFF the ignition.
Remove the fuel fuse.
Remove the ignition coil assembly from the affected bank cylinder. Do not disconnect any electrical connectors from the ignition coil assembly. Refer to Ignition Coil Replacement - Bank 1 or Ignition Coil Replacement - Bank 2 .
Install the J 36012-A Ignition Diagnostic Harness.
Install the J 26792 Spark Tester on one of the spark plug jumper wires of the affected cylinders.
Crank the engine with the remaining spark plug jumper wires connected.

Did the spark tester spark on all cylinders?

Go to Step 7

Go to Electronic Ignition (EI) System Diagnosis

Remove the spark plugs from the cylinders that indicated a misfire.
Inspect the spark plug. Refer to Spark Plug Inspection .

Does the spark plug appear to be OK?

Go to Step 8

Go to Step 9

Exchange the suspected spark plug with another cylinder that is operating properly. Refer to Spark Plug Replacement .
Operate the vehicle under the same conditions that the misfire occurred.

Did the misfire move with the spark plug?

Go to Step 15

Go to Step 12

Are the spark plugs oil or coolant fouled?

Go to Symptoms - Engine Mechanical in Engine Mechanical

Go to Step 10

Are the spark plugs gas fouled?

Go to Step 13

Go to Step 11

Do the spark plugs show any signs of being cracked, worn, or improperly gapped?

Go to Step 14

Go to Step 12

Perform the fuel injector coil test. Refer to Fuel Injector Solenoid Coil Test .

Did you find and correct the condition?

Go to Step 16

Go to Symptoms - Engine Mechanical in Engine Mechanical

Perform the fuel system diagnosis. Refer to Fuel System Diagnosis .

Did you find and correct the condition?

Go to Step 16

Go to Symptoms - Engine Mechanical in Engine Mechanical

Replace or gap the spark plug. Refer to Spark Plug Replacement .

Did you complete the action?

Go to Step 16

Replace the faulty spark plugs. Refer to Spark Plug Replacement .

Did you complete the replacement?

Go to Step 16

Was the customer concern the malfunction indicator lamp (MIL) flashing?

Go to Step 17

Go to Step 18

Operate the vehicle at the specified value for 4 minutes.
Operate the vehicle within the Conditions for Running the DTC P0420 or P0430 as specified in the supporting text. Refer to DTC P0420 or P0430 .

Does the DTC run and pass?

2,500 RPM

Go to Step 18

Go to DTC P0420 or P0430

Clear the DTCs with a scan tool.
Turn OFF the ignition for 30 seconds.
Start the engine.
Operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records.

Did the DTC fail this ignition?

Go to Step 2

Go to Step 19

Observe the Capture Info with a scan tool.

Are there any DTCs that have not been diagnosed?

Go to Diagnostic Trouble Code (DTC) List - Vehicle in Vehicle DTC Information

System OK