Tip & How-To about Mercedes-Benz E-Class

CMP - Cam shaft Position Sensor

3.2) CMP - Cam shaft Position (sensor)



What is it? This electrical device is very similar in concept to the crank position sensor (above) in that it detects the position of the rotation of a shaft, in this instance the cam shaft. It is the cam shaft signal that indicates to the ECU that cylinder one is at top dead centre at compression and in the process provides the ECU with the timing reference for fuel injection. The cam shaft sensor provides extra information, to that of the crank sensor, to fine tune timed events such as injection and spark delivery.


Where is it located? The location of this device depends on the design and age of engine. On many modern overhead cam shaft engines the cam shaft sensor is located either on the end, or to the side of the end, of the cam shaft housing. On older pushrod engines the cam sensor is found where the distributor would once have been located. This type sensor assembly makes use of the distributor shaft meshing directly, at its bottom end, with a gear on the cam within the engine block. In this respect the distributor shaft is just an extension of the cam shaft. On the top end of this distributor shaft is a magnetic armature. The cam shaft sensor, that measures the movement of this armature, is located in the cover and uses either magnetic or 'Hall effect' pickup modules.


How does it work? The sensor detects the position of a magnet or set of teeth on the gear on the end of the cam. An electrical waveform output signal is sent to the ECU as the cam turns. The cam sensor tells the ECU that cylinder 1 is at TDC on its compression stroke prior to ignition. The cam sensor ensures the correct timing of the fuel injection cycle. If the timing belt ever jumps a tooth on the cam the lack of agreement between the respective signals from the cam and crank sensors is indicated as an error condition by the ECU.


Symptoms of faulty cam sensor

Associated OBD2 error codes DTCs: P0341 - P0349; P1345


  • Hesitant acceleration - miss-timing of fuel injection due to a faulty CMP can cause intermittent loss of power.
  • Starting difficulty/failure. If the faulty CMP timing problems are severe they may cause the engine not fire at all, or to fire and then stall, or stall at some random time without warning.
  • Hot engine stall and failure to restart - Sometimes the fault of the CSS only manifests itself when the engine is hot. Over time thermal stress can cause cracking and can weaken electrical junctions within the CMP. The CMP may work well at cold start up but can then cause a hot running engine to stop with little chance of restart whilst the engine is still hot; once cooled the down the engine may readily restart and again run for a limited period until hot.

Note The cam sensor body often protrudes into the cam shaft gallery and when it's 'o' ring seal becomes age hardened, engine oil may leak back into the sensor electrical socket plug connector causing errors due to interruption of signal.


How to check? It is not technically easy to determine that the CMP is at fault and, like the crank sensor, may require the use of an oscilloscope. If it is part of a sophisticated on board diagnostics system its failure may be logged as a specific error code in the ECU. Due to the variability problems with engine running are often experienced well before any error codes are set by the ECU.


2 pin socket (magnetic - sine wave output). One pin is 'ground' the other is 'signal'. A voltmeter set to 2 volts AC should measure a signal in the 0.2 to 2 volts range on the 'signal' pin.

3 pin socket (Hall effect, magneto - square wave form output). One pin is 'reference' (5volts), one pin is 'ground' and the third pin is 'signal'. A DC voltage should be detectable in the 0.5 to 1.5 volt range from the 'signal' pin.

It is important that the voltage measurement take place at start up when the engine is cold and again, 20 minutes later, when the engine has fully warmed up to operating temperature. Often the voltage output from faulty sensors declines with temperature rise.


How to fix? If the CMP failure is due oil leakage into the electrical connector then a thorough clean and a renewal of the oil seal on the CMP may correct the situation. It can be a wise precaution to change the connecting cable as oil migration beneath the insulation may possibly contaminate components at some distance to the CMP.

If the CMP has an internal fault then it must be replaced.

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where is cam shaft sensor located on a 08 saturn aura


Which engine ? This vehicle had option of six different engines , 2.4 , 3.5 , 2.8 , 3.0 , 3.2 , 3.6 And are you picking on the right part ? What code > DTC P0010: Intake Camshaft Position (CMP) Actuator Solenoid Control Circuit

DTC P0013: Exhaust Camshaft Position (CMP) Actuator Solenoid Control Circuit
It may not even be a cam sensor problem !
DTC P0340: Intake CMP Sensor Circuit

DTC P0365: Exhaust Camshaft Position (CMP) Sensor Circuit
DTC P0341: Intake Camshaft Position (CMP) Sensor Performance

DTC P0366: Exhaust Camshaft Position (CMP) Sensor Performance
Camshaft Position (CMP) Actuator System
The camshaft position (CMP) actuator system is an electro-hydraulic operated device used for a variety of engine performance and operational enhancements. These enhancements include lower emission output through exhaust gas dilution of the intake charge in the combustion chamber, a broader engine torque range, and improved fuel economy. The CMP actuator system accomplishes this by changing the angle or timing of the camshaft relative to the crankshaft position. The CMP actuator simply allows earlier or later intake and exhaust valve opening during the four stroke engine cycle. The CMP actuator cannot vary the duration of valve opening, or the valve lift.
During engine OFF, engine idling conditions, and engine shutdown, the camshaft actuator is held in the Park position. Internal to the CMP actuator assembly is a return spring and a locking pin. During non-phasing modes of the camshaft, the return spring rotates the camshaft back to the Park position, and the locking pin retains the CMP actuator sprocket to the camshaft


It may

Jul 06, 2016 | 2008 Saturn Aura

1 Answer

03 Chevy 2500HD 6.0 Gas I have no power to the 10A fuse for the crank with the key on or off truck does start. A P0342 code keep coming up


code p0342 refers to cam shaft position (CMP) sensor A bank 1 --low input===causes--wiring short to ground---CMP sensor---ECM
Check for wiring shorting out on the engine /body, replace the cam sensor on bank 1

Jan 31, 2015 | Cars & Trucks

1 Answer

Where does the cam position sencer located at


It's officially called a CMP Syncronizer.
There are stern warnings on the page associated with this.
CAMSHAFT POSITION (CMP) SENSOR Removal & Installation
CMP sensor is located on rear of engine, behind intake manifold. Before removing, note position of electrical connector on CMP sensor. Remove upper intake manifold. See UPPER INTAKE MANIFOLD . Disconnect CMP sensor. Remove CMP sensor screws and CMP sensor. To install, reverse removal procedure. Ensure CMP sensor electrical connector is pointing in original direction. Tighten CMP sensor to specification.
2 . Failure to use synchro positioner during installation will cause fuel injection to be out of time and may cause engine damage.
CAUTION: DO NOT rotate crankshaft when Synchro Positioner (T95T-12200-A) is positioned on CMP synchronizer. Armature tab will be damaged and synchronizer timing may be shifted. Removal
1. Position crankshaft to TDC of cylinder No. 1, on compression stroke. Note position of electrical connector on CMP sensor. 2. Disconnect negative battery cable. Unplug harness connector from CMP sensor. Remove CMP sensor screws and CMP sensor from positioner. Remove synchronizer hold-down bolt and CMP synchronizer.
Fig. 2: Exploded View Of CMP Synchronizer Assembly (Typical) Courtesy of FORD MOTOR CO.
CAUTION: DO NOT rotate crankshaft while synchronizer is removed from engine. Installation
1. Install Synchro Positioner (T95T-12200-A) on synchronizer housing. See Fig. 3 . Rotate synchronizer shaft until vane on shaft aligns with slot on synchro positioner. Rotate synchro positioner until engaged into notch in housing. Dip drive gear in engine oil.
Fig. 3: Installing Synchro Positioner On Synchronizer Assembly (Typical) Courtesy of FORD MOTOR CO.
Fig. 4: Positioning Synchronizer For Installation Courtesy of FORD MOTOR CO. 2. Rotate sychronizer assembly so that synchro positioner is 60 degrees counterclockwise of crankshaft centerline before inserting synchronizer assembly into engine. See Fig. 4 . 3. As synchronizer is inserted into engine, synchronizer will rotate. When seated, synchronizer electrical connector should be located in original position.
CAUTION: If CMP sensor electrical connector is not positioned correctly, DO NOT reposition connector by rotating synchronizer. This may cause fuel system to be out of time with the engine, causing possible engine damage or an engine misfire. Remove synchronizer and reinstall. See step 3 . 4. Install hold-down clamp and tighten bolt to specification. See TORQUE SPECIFICATIONS . Install CMP sensor to synchronizer and tighten to specification. Ensure CMP sensor electrical connector is in original position. Reconnect wiring to CMP sensor. Connect negative battery cable.
fig2explodedviewofcmpsy.gif

May 03, 2011 | 1995 Ford Explorer

2 Answers

Toyota ipsum 2002 check light comes on with code P1346.


Definition of Diagnostic Trouble Code P1346 Audi: Ignition Coil Power Output Stage 3 Short to B+ BMW: Misfire During Start Cylinder 3 Buick: Intake Camshaft Position [CMP] Sensor System Performance Cadillac: Intake Camshaft Position [CMP] Sensor System Performance Chevrolet: Intake Camshaft Position [CMP] Sensor System Performance Ford: Fuel Level Sensor B Circuit GMC: Intake Camshaft Position [CMP] Sensor System Performance Lexus: VVT Sensor Rang/Performance Problem (Bank 1) Lincoln: Fuel Level Sensor B Circuit Mazda: Fuel Level Sensor B Circuit Mercury: Fuel Level Sensor B Circuit Oldsmobile: Intake Camshaft Position [CMP] Sensor System Performance Pontiac: Intake Camshaft Position [CMP] Sensor System Performance Saturn: Intake Camshaft Position [CMP] Sensor System Performance Toyota: VVT Sensor /Camshaft Position Sensor Circuit Range/ Performance Problem (Bank 1) Volkswagen: Ignition Coil Power Output Stage 3 Short to B+

Mar 12, 2010 | 2001 Toyota Sienna

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