Camshaft Position (CMP) Sensor, Checking

Camshaft Position (CMP) Sensor, Checking

The Camshaft Position (CMP) sensor -G40- is located on the rear of the left cylinder head. Testing and Inspection


NOTE:
- During normal engine operation the ECM, using the CMP sensor signal, recognizes the ignition point for cylinder 1 and initiates ignition for each cylinder at every second crankshaft revolution.
- The engine will start or run with a faulty or disconnected CMP sensor, since the ECM initiates ignition for each cylinder with every crankshaft revolution after recognizing the malfunction.
- For the fuel injection, being off by one crankshaft revolution has no noticeable effect. Fuel is injected against the closed intake valve, instead of taking place while the valve is open. The quality of the fuel-air mixture is not significantly affected


Checking CMP sensor signal
- Push back protective rubber boot at back of CMP sensor harness connector (CMP sensor remains connected).







- Connect VAG1527B LED voltage tester between connector terminals 1 and 2 (from the back).


NOTE: Harness connector terminals are numbered on the back side of the connector.


- Briefly operate starter motor.
LED must flash.

If LED does not flash:
- Check CMP sensor power supply.

Checking CMP sensor power supply
- Disconnect CMP sensor harness connector.
- Switch ignition on.
- Connect multimeter US 1119 (Fluke 83 or equivalent) between CMP connector terminal 1 and engine Ground.
Specified value: 4.5 - 5.5 volts

Checking CMP sensor signal wiring
- Connect multimeter US 1119 (Fluke 83 or equivalent) between CMP connector terminal 2 and engine Ground.
- Switch ignition on.
Specified values: Battery Positive Voltage (B+)
- Switch ignition off.

Checking CMP sensor Ground connection
- Connect multimeter US 1119 (Fluke 83 or equivalent) and check resistance between CMP sensor connector terminal 3 and engine Ground.
Specified value: Continuity

If there is not continuity, and the LED does not flash:
- Replace CMP sensor.
- Check readiness code. If Diagnostic Trouble Code (DTC) memory has been erased, then generate new readiness code.
Refer "Monitors, Trips and/or Drive Cycle (Readiness Code)/Checking, Readiness Code" Testing and Inspection
Refer "Monitors, Trips and/or Drive Cycle (Readiness Code)/Generating, Readiness Code" Testing and Inspection

If one of the specified values was not obtained:
- Connect VAG1598/19 test box to Engine Control Module (ECM) harness connector Refer "Scan Tool Testing/Scan Tool Connecting and Initial Checks/VAG1598/19 Test Box, Connecting" Testing and Inspection







- Check wiring for open circuit, short circuit to B+ or short to Ground between CMP sensor and ECM.

CMP sensor VAG1598/19 socket (ECM terminal)
connector terminal
1 A3 (+5 volts)
2 B2 (signal)
3 D12(Ground)







If, after erasing Diagnostic Trouble Code (DTC) memory, CMP sensor malfunctions are still stored, and all test results to this point have been OK:
- Remove CMP sensor.
- Make sure that trigger wheel is correctly installed.
(Can be damaged if mounting bolts are incorrectly torqued).

If CMP sensor trigger wheel is OK:
- Check camshaft drive belt adjustment.