GM Service Manual Online
For 1990-2009 cars only

Diagnostic Instructions

    • Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure.
    • Review Strategy Based Diagnosis for an overview of the diagnostic approach.
    •  Diagnostic Procedure Instructions provide an overview of each diagnostic category.

DTC Descriptors

DTC P0341: Camshaft Position (CMP) Sensor Performance

Diagnostic Fault Information

Circuit

Short to Ground

Open/High Resistance

Short to Voltage

Signal Performance

5-Volt Reference Circuit

P0641, P0452

P0340

P0533, P0641

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CMP Sensor Signal Circuit

P0340

P0340

P0340

P0341

Low Reference Circuit

--

P0340

--

--

Circuit/System Description

The 4X camshaft position (CMP) sensor circuits consist of an engine control module (ECM) supplied 5-volt reference circuit, low reference circuit, and an output signal circuit. The CMP sensor is an internally magnetic biased digital output integrated circuit sensing device. The sensor detects magnetic flux changes of the teeth and slots of a 4-tooth reluctor wheel attached to the camshaft. As each reluctor wheel tooth rotates past the CMP sensor, the resulting change in the magnetic field is used by the sensor electronics to produce a digital output pulse. The sensor returns a digital ON/OFF DC voltage pulse of varying frequency, with 4 varying width output pulses per camshaft revolution that represent an image of the camshaft reluctor wheel. The frequency of the CMP sensor output depends on the velocity of the camshaft. The ECM decodes the narrow and wide tooth pattern to identify camshaft position. This information is then used to determine the optimum ignition and injection points of the engine. The ECM also uses CMP sensor output information to determine the camshaft relative position to the crankshaft, to control camshaft phasing, and for limp-home operation.

Conditions for Running the DTC

    • DTC P0641 or P0651 is not set.
    • The engine is cranking or running.
    • The DTCs run continuously when the above conditions are met.

Conditions for Setting the DTC

       Important: The ECM detects engine movement by sensing the airflow through the mass air flow (MAF) sensor is more than 3 g/s, or by sensing crankshaft position (CKP) sensor pulses.

    • The ECM detects that the engine has started, but has received either of the following during the first engine revolution:
       - Less than or more than 4 CMP sensor pulses, if equipped with an automatic transmission
       - less than 4 or more than 6 CMP sensor pulses, if equipped with a manual transmission
       - OR
    • The ECM detects that the engine is running, but receives less than 397 CMP or more than 403 CMP sensor pulses per 100 engine cycles in 800 of 1000 engine cycles.

Action Taken When the DTC Sets

DTC P0341 is a Type B DTC.

Conditions for Clearing the MIL/DTC

DTC P0341 is a Type B DTC.

Diagnostic Aids

Inspect the 10-way engine harness to fuel injector harness connector, the CMP sensor connector, and the ECM connector for corrosion.

Reference Information

Schematic Reference

Engine Controls Schematics

Connector End View Reference

Component Connector End Views

Electrical Information Reference

    •  Circuit Testing
    •  Connector Repairs
    •  Testing for Intermittent Conditions and Poor Connections
    •  Wiring Repairs

DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions

Scan Tool Reference

Control Module References for scan tool information

Circuit/System Verification

  1. Ignition OFF, inspect the engine wiring harness carrying the CMP sensor circuits for the following conditions:
  2. • Close routing of aftermarket electrical equipment
    • Close to solenoids, motors, and relays
         ⇒Correct any wire harness routing or component placement conditions, if it is determined to be a possible source of electrical interference.
  3. Start the engine. Using the Live Plot function on the scan tool, select the CMP parameter. Change the minimum spec to 400 RPM and the maximum spec to 4,000 RPM. Select the CKP sensor parameter. Change the minimum spec to 600 RPM, and the maximum spec to 3,300 RPM.
  4. Observe the scan tool.
  5. Quickly accelerate and release the accelerator pedal several times. Do not accelerate past 3,200 RPM. The graphed lines on the Live Plot display should track together across the screen.
  6. If the vehicle passes the Circuit/System Verification test, operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that are captured in the Freeze Frame/Failure Records data list.

Circuit/System Testing

  1. Ignition OFF, inspect the CMP sensor for correct installation.
  2. If the CMP sensor is loose, inspect the sensor and the O-ring for damage. Replace as necessary.
  3. Inspect the engine for the following conditions:
  4. • Engine oil for debris
    • Camshaft reluctor wheel for damage
    • The timing chain, timing chain tensioner, and sprockets for wear or damage
         ⇒If debris is found in the engine oil, inspect the internal engine components to determine the root cause. Repair or replace any worn or damaged components.

Component Testing

Important: You must perform the Circuit/System Testing before proceeding with Component Testing.

  1. Inspect the CMP sensor for correct installation. Remove the CMP sensor from the engine and inspect the sensor O-ring for damage.
  2. If the sensor is loose, incorrectly installed, or damaged, replace the CMP sensor.
  3. Connect the CMP sensor harness connector to the CMP sensor.
  4. Ignition ON, engine OFF, observe the CMP Active counter parameter on the scan tool.
  5. Pass a flat steel object across the tip of the sensor repeatedly. The CMP Active counter parameter should increment with each pass of the steel object.
  6. If the parameter does not increment, replace the CMP sensor.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

    •  Camshaft Position Sensor Replacement
    •  Control Module References for ECM replacement, setup, and programming