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For 1990-2009 cars only
Makes 🢒 Chevrolet 🢒 2006 🢒 Cobalt 🢒 Vehicle Control Systems 🢒 Vehicle DTC Information 🢒 DTC P0340

Circuit Description

This ignition system does not use a conventional camshaft position (CMP) sensor that detects valve train position. The ignition control module (ICM) detects when #1 or #3 cylinder has fired on the cylinders compression stroke using sensing circuitry integrated within each coil. The sensing circuit detects the polarity and the strength of the secondary voltage output. The higher output is always at the event cylinder. The ICM sends a CMP signal to the engine control module (ECM) based on the voltage difference between the event and waste cylinder firing energy. This system is called compression sense ignition. By monitoring the CMP and crankshaft position (CKP) signals, the ECM can accurately sequence the fuel injectors. If the ECM does not receive a CMP signal from the ICM, DTC P0340 sets.

DTC Description

This diagnostic procedure supports the following DTC:

DTC P0340 Camshaft Postion (CMP) Sensor Circuit

Conditions for Running the DTC
    • The engine is running.
    • The manifold absolute pressure (MAP) is more than 30 kPa.

Conditions for Setting the DTC

The ECM does not detect any change in the CMP sensor signal for 107 crankshaft revolutions when the MAP is at 30 kPa or more.

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 control module turns OFF the malfunction indicator lamp (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail.
    • A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
    • A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
    • Clear the MIL and the DTC with a scan tool.

Diagnostic Aids
    •  An intermittent crank signal will result in an interrupted cam signal and may set this DTC.
    • The following conditions may cause this DTC to set:
       - High resistance in the #1 secondary ignition system
       - Low resistance in the #4 secondary ignition system
       - Corroded or loose #1 or #4 secondary ignition components
    • If this DTC is determined to be intermittent, refer to Intermittent Conditions .

Test Description

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

  1. If CYL #1 and/or CYL #4 Misfire Counters are incrementing there is a condition within the secondary ignition system that effects the camshaft position signal circuit.

  2. The ECM supplies 5 volts on the camshaft position signal circuit. This step determines if the ECM is supplying the correct voltage on the circuit.

Step

Action

Values

Yes

No

Schematic Reference: Engine Controls Schematics

1

Did you perform the Diagnostic System Check - Vehicle?

--

Go to Step 2

Go to Diagnostic System Check - Vehicle

2
  1. Start the engine.
  2. Observe the CMP Active Counter with a scan tool.

Does the CMP Active Counter parameter increment and then reset to 0 continuously?

--

Go to Step 3

Go to Step 4

3
  1. Observe the Freeze Frame/Failure Records for this DTC.
  2. Turn OFF the ignition for 30  seconds.
  3. Start the engine.
  4. 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 4

Go to Diagnostic Aids

4

Observe the Misfire Current CYL # 1 and CYL # 4 counters with a scan tool.

Is CYL #1 and/or CYL #4 Misfire counters counting up?

--

Go to DTC P0300

Go to Step 5

5
  1. Turn OFF the ignition.
  2. Disconnect the ignition control module (ICM).
  3. Jumper the ICM circuits except for the camshaft position signal circuit from the ICM to the ICM harness connector. Refer to Using Connector Test Adapters .
  4. Measure the DC duty cycle on the camshaft position signal circuit of the ICM with a DMM. Refer to Circuit Testing .
  5. Start the engine.

Is the Duty Cycle within the specified range?

45-55%

Go to Step 6

Go to Step 10

6

  1. Turn OFF the ignition.
  2. Remove the jumper wires from the ICM.
  3. Leave the ICM disconnected.
  4. Turn ON the ignition, with the engine OFF.
  5. Measure the voltage on the camshaft position signal circuit at the ICM harness connector with a DMM connected to ground. Refer to Circuit Testing .

Is the voltage within the specified range?

4-6 V

Go to Step 8

Go to Step 7

7

Is the voltage above the specified range?

4-6 V

Go to Step 11

Go to Step 8

8
  1. Turn OFF the ignition.
  2. Disconnect the engine control module (ECM).
  3. Measure the resistance of the camshaft position signal circuit with a DMM. Refer to Circuit Testing .

Is the resistance within the specified range?

0-5 ohms

Go to Step 9

Go to Step 12

9
  1. Leave the ECM and ICM disconnected.
  2. Measure the resistance from the camshaft position signal circuit of the ICM harness connector to a good ground with a DMM. Refer to Circuit Testing .

Is the resistance at the specified value?

OL

Go to Step 16

Go to Step 13

10
  1. Turn OFF the ignition.
  2. Remove the ICM from the ignition coil housing. Refer to Ignition Control Module Replacement .
  3. Remove the interconnect from between the ignition coil housing and the ICM.
  4. Inspect the interconnect for a poor connection at the coil housing and at the ICM. Refer to Testing for Intermittent Conditions and Poor Connections .

Did you find and correct the condition?

--

Go to Step 18

Go to Step 14

11

Test the camshaft position signal circuit for a short to voltage. Refer to Circuit Testing and Wiring Repairs .

Did you find and correct the condition?

--

Go to Step 18

Go to Step 16

12

Test the camshaft position signal circuit for an open or high resistance. Refer to Circuit Testing and Wiring Repairs .

Did you find and correct the condition?

--

Go to Step 18

Go to Step 16

13

Test the camshaft position signal circuit for a short to ground. Refer to Circuit Testing and Wiring Repairs .

Did you find and correct the condition?

--

Go to Step 18

Go to Step 16

14

Test for an intermittent and for a poor connection at the ICM. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs .

Did you find and correct the condition?

--

Go to Step 18

Go to Step 15

15

Replace the ICM. Refer to Ignition Control Module Replacement .

Did you complete the replacement?

--

Go to Step 18

--

16

Test for an intermittent and for a poor connection at the ECM. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs .

Did you find and correct the condition?

--

Go to Step 18

Go to Step 17

17

Replace the ECM. Refer to Control Module References for replacement, setup, and programming.

Did you complete the replacement?

--

Go to Step 18

--

18
  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. 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

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

System OK