GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Cadillac 🢒 2003 🢒 CTS - RHD 🢒 Engine 🢒 Engine Controls - 2.6L and 3.2L 🢒 DTC P0301-P0306

Circuit 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 PCM 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 preset. DTCs P0301-P0306 correspond to cylinders 1-6. If the ECM is able to determine that a specific cylinder is misfiring, the DTC for that cylinder will set.

Conditions for Running the DTC
    • DTCs P0121, P0122, P0123, P0222, P0223, P0335, P0336, P0337, P0338, P0341, P0342, P0343, P0440, P0443, P0444, or P0445 are not set.
    • The engine speed is between 520-6,520 RPM.
    • The torque management is not active.
    • The anti-lock brake/traction control (ABS/TC) system is not active.
    • The ECM is not receiving a rough road signal.
    • The fuel cut-off is not active, including the traction control, the deceleration, the high speed/RPM .
    • The engine has been running for longer than 5 seconds.
    • The intake air temperature (IAT) is more than -8°C (17°F).

Conditions for Setting the DTC

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

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 three 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 forty 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

A misfire DTC could be caused by an excessive vibration from sources other than the engine. Check for the following possible sources:

    • Tire or wheel out of round or balance
    • Variable thickness brake rotor or drum
    • Drive shaft not balanced
    • Certain rough road conditions
    • Damaged accessory drive belt

Test Description

The numbers below refer to the step numbers on the diagnostic table.

  1. DTCs that may cause a misfire DTC to set may include those for injector control circuits, oxygen sensors, the EVAP system, or fuel trim.

    2.

  2. This test is to determine if there is a problem in the heated oxygen sensor (HO2S) or wiring that is causing the ECM to alter the fuel trim. When the sensors are disconnected, the fuel system should go into Open Loop.

Step

Action

Values

Yes

No

1

Did you perform the Diagnostic System Check-Engine Controls?

--

Go to Step 2

Go to Diagnostic System Check - Engine Controls

2

Are any DTCs other than DTC P0300 or P0301-P0306 set?

--

Go to Diagnostic Trouble Code (DTC) List

Go to Step 3

3
  1. Start the engine.
  2. Allow the engine to idle or operate within the conditions listed in the Freeze Frame/Failure Records.
  3. Observe the Misfire Current Counter for this cylinder with a scan tool.

Is the Misfire Current Counter incrementing?

--

Go to Step 4

Go to Diagnostic Aids

4

Does the scan tool indicate that any HO2S voltage parameters are fixed above the specified value?

200 mV

Go to DTC P0131, P0137, P0151, or P0157

Go to Step 5

5

Does the scan tool indicate that any HO2S voltage parameters are fixed below the specified value?

900 mV

Go to DTC P0132 or P0152

Go to Step 6

6

Visually/physically inspect the following items:

    • The vacuum hoses for splits, kinks and proper connections
    • The throttle body and the intake manifold for vacuum leaks
    • The crankcase ventilation valve and/or system for vacuum leaks
    • Ensure that the ECM grounds are clean and secure.

Did you find and correct the condition?

--

Go to Step 10

Go to Step 7

7
  1. Perform the injector balance test. Refer to Fuel Injector Balance Test with Special Tool and Fuel Injector Solenoid Coil Test on the affected cylinder.
  2. Repair as necessary.

Did you find and correct the condition?

--

Go to Step 10

Go to Step 8

8
  1. Perform the ignition system check. Refer to Electronic Ignition (EI) System Diagnosis .
  2. Repair as necessary.

Did you find and correct the condition?

--

Go to Step 10

Go to Step 9

9

  1. Turn OFF the ignition.
  2. Disconnect both HO2S 1 connectors.
  3. Start and idle the engine.
  4. Using the scan tool, monitor the Misfire Current Counter for this cylinder.

Is the Misfire Current Counter incrementing?

--

Go to Symptoms - Engine Mechanical in Engine Mechanical

Go to DTC P0130, P0136, P0150, or P0156

10
  1. Clear the DTCs with a scan tool.
  2. Turn OFF the ignition for 30 seconds.
  3. Start the engine.
  4. Operate the vehicle within the Conditions for Running the DTC as specified in the supporting text.

Does the DTC run and pass?

--

Go to Step 11

Go to Step 2

11

With a scan tool, observe the stored information, Capture Info.

Does the scan tool display any DTCs that you have not diagnosed?

--

Go to Diagnostic Trouble Code (DTC) List

System OK