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For 1990-2009 cars only
Makes 🢒 Cadillac 🢒 1999 🢒 Catera 🢒 DTC 🢒 DTC P0340 Camshaft Position (CMP) Sensor Circuit

Object Number: 414201 Size: MF
Handling ESD Sensitive Parts Notice
Engine Controls Components
Cell 20: Engine Data Sensors
OBD II Symbol Description Notice

Circuit Description

The camshaft position (CMP) sensor works in conjunction with a single tooth reluctor wheel on the Bank 2 Intake camshaft. The ECM pulls up the CMP sensor signal circuit to 5 volts and monitors this voltage. As the reluctor wheel tooth rotates past the sensor, the sensor's internal circuitry pulls the signal circuit to ground, creating a square wave signal that is used by the ECM. The reluctor wheel tooth covers 180 degrees of the camshaft circumference. This causes the CMP signal voltage to transition once per crankshaft revolution. This signal, when combined with the CKP sensor signal, enables the ECM to determine exactly which cylinder is on a firing stroke. The ECM can then properly synchronize the ignition system, the fuel injectors and the knock control. Note that as long as the CKP signal is available, the engine can start even if there is no CMP sensor signal. The ECM will default to a non-sequential fuel injector operation.

Conditions for Running the DTC

The engine speed is greater than 20 RPM.

Conditions for Setting the DTC

The CMP signal is incorrect for at least 5 cycles.

Action Taken When the DTC Sets
    • The ECM illuminates the malfunction indicator lamp (MIL) and records the operating conditions in the Freeze Frame on the second consecutive drive trip that the diagnostic runs and fails.
    • The ECM will use a calculated spark retard value in order to minimize a knock during conditions when a knock is likely to occur. The calculated value will vary based on the engine speed and load.

Conditions for Clearing the MIL/DTC
    • The ECM turns OFF the MIL after three consecutive drive trips that the diagnostic runs and passes.
    • A History DTC clears after forty consecutive warm-up cycles in which no failures are reported by this diagnostic or any other emission related diagnostic.
    • The ECM battery voltage is interrupted.
    • The scan tool clears the MIL/DTC.

Diagnostic Aids

Notice: Using the J 35616-A Connector Test Adapter Kit will prevent damage to the harness connector terminals.

Use the J 35616 Connector Test Adapter Kit for any test that requires probing the ECM harness connector or a component harness connector.

Check for the following conditions:

    • Poor connections at the ECM or at the component--Inspect the harness connectors for any backed out terminals, improper mating, broken locks, improperly formed or damaged terminals, and poor terminal to wire connection. Refer to Wiring Repairs , or Engine Control Module Diagnosis , Checking Terminal Contact for the proper procedure.
    • Misrouted harness--Inspect the harness in order to ensure that the harness is not routed too close to any high voltage wires such as spark plug leads, or too close to any high current devices such as the alternator, the motors, the solenoids, etc.
    • Damaged harness--Inspect the wiring harness for any damage. If the harness appears to be OK, observe the scan tool while moving the related connectors and the wiring harnesses. A change in the display may help in order to locate the fault.
        If the sensor signal is only affected when the harness is moved at a component, and there is no problem with the harness or the connections, the component may be damaged.
    •  Check the sensor for a proper installation. A sensor that is loose or not fully seated (causing an excessive air gap between the sensor and the reluctor wheel) may cause this DTC to set.

Refer to Symptoms for the intermittents.

Test Description

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

  1. This step checks for proper switched B+ to the sensor.

    2.

  2. This step checks for a proper ground to the sensor.

    3.

  3. This step checks for the proper ECM pull-up voltage to the sensor.

    4.

  4. This step checks if the CMP sensor can produce a signal to the ECM.

DTC P0340 - Camshaft Position (CMP) Sensor Circuit

Step

Action

Values

Yes

No

1

Did you perform the Powertrain On-Board Diagnostic (OBD) System check?

--

Go to Step 2

Go to Powertrain On Board Diagnostic (OBD) System Check

2
  1. Clear the DTCs with the scan tool.
  2. Crank the engine for 10 seconds or until it starts.
  3. Using the scan tool, inspect the DTC Information.

Does this DTC set?

--

Go to Step 3

Go to Diagnostic Aids

3

  1. Turn OFF the ignition.
  2. Disconnect the CMP sensor connector.
  3. Turn ON the ignition with the engine OFF.

    4. Important: Do not use the CMP sensor shielded ground circuit for the following test. Internal ECM damage could result.

  4. Probe the CMP sensor switch battery positive circuit in the harness connector (ECM side) with the test light J 34142-B connected to a known good ground.

Does the test light illuminate?

--

Go to Step 4

Go to Step 9

4

  1. Turn OFF the scan tool. The scan tool must be turned OFF in order to allow the ECM to power down when the ignition is turned OFF.
  2. Turn the ignition OFF.
  3. Wait 30 seconds in order to allow the ECM to power down. Inaccurate test results will occur if the ECM is not powered down.
  4. Measure the resistance between the CMP sensor shielded ground circuit and the ECM bracket ground stud using the J 39200 DMM.

Is the resistance less than the value specified?

5 ohms

Go to Step 5

Go to Step 11

5

  1. Turn the ignition ON leaving the engine OFF.
  2. Measure the voltage from the CMP sensor signal circuit to the CMP sensor shielded ground circuit using the J 39200 DMM.

Is the voltage within the specified value range?

4.8-5.2 V

Go to Step 6

Go to Step 7

6

  1. Turn OFF the ignition.
  2. Connect the CMP sensor connector.
  3. Disconnect the ECM.
  4. Jumper the Engine Controls Power Relay control circuit to ground in order to supply power to the CMP sensor.
  5. Connect the J 34142-B test light between the CMP sensor signal circuit at the ECM connector and BATTERY POSITIVE.
  6. Observe the test light while cranking the engine (the engine will not start).

Does the test light blink while the engine is cranking?

--

Go to Step 14

Go to Step 12

7

Was the voltage greater than the specified value?

5.2 V

Go to Step 10

Go to Step 8

8
  1. Turn OFF the ignition.
  2. Disconnect the ECM.
  3. Check the harness for continuity of the CMP sensor signal circuit with the J 39200 DMM between the CMP sensor connector and the ECM connector. The DMM should indicate very low resistance.
  4. Check the harness for continuity of the CMP sensor signal circuit with the J 39200 DMM between the CMP sensor connector and ground. The DMM should indicate OL.
  5. Repair the wiring as necessary. Refer to Wiring Repairs in Wiring Systems.

Was a problem found and corrected?

--

Go to Step 16

Go to Step 14

9

Repair the Switched B+ circuit. Refer to Wiring Repairs in Wiring Systems.

Is the action complete?

--

Go to Step 16

--

10

Repair the signal circuit shorted to B+. Refer to Wiring Repairs in Wiring Systems.

Is the action complete?

--

Go to Step 16

--

11
  1. Disconnect the ECM.
  2. Inspect the CMP sensor shielded ground circuit for continuity between the CMP sensor connector and the ECM connector.
  3. Repair the open/high resistance in the CMP sensor shielded ground circuit if necessary. Refer to Wiring Repairs in Wiring Systems.

Was a problem found and corrected?

--

Go to Step 16

Go to Step 14

12

Check the CMP sensor for the following conditions:

    • Check for poor connections/terminal tension at the CMP sensor harness connector. Refer to Checking Terminal Contact in Engine Control Module Diagnosis .
    • Check the sensor for proper installation. A sensor that is loose or not fully seated could cause an excessive air gap between the sensor and the reluctor wheel.

Was a problem found and corrected?

--

Go to Step 16

Go to Step 13

13

Replace the CMP sensor. Refer to Camshaft Position Sensor Replacement .

Is the action complete?

--

Go to Step 16

--

14

Check for a poor connection or poor terminal tension at the ECM harness connector. Refer to Electrical Diagnosis in Engine Electrical, and Troubleshooting Procedures for the proper procedure. Also, refer to Checking Terminal Contact in Engine Control Module Diagnosis .

Was a problem found and corrected?

--

Go to Step 16

Go to Step 15

15

Important: This vehicle is equipped with a Theft Deterrent System which interfaces with the Engine Control Module (ECM). Program the new ECM with the frequency code of the theft deterrent module that is currently on the vehicle.

Replace the ECM. Refer to Engine Control Module Replacement/Programming .

Is the action complete?

--

Go to Step 16

--

16
  1. Use a scan tool in order to clear the DTCs.
  2. Start the engine.
  3. Allow the engine to idle until the engine reaches the normal operating temperature.
  4. Select the DTC and the Specific DTC function.
  5. Enter the DTC number that was set.
  6. Operate the engine within the Conditions for Running this DTC until the scan tool indicates the diagnostic Ran.

Does the scan tool indicate the diagnostic Passed?

--

Go to Step 17

Go to Step 2

17

Does the scan tool display any additional, undiagnosed DTCs?

--

Go to the applicable DTC table

System OK