Camshaft Position (CMP) Sensor -G40-, Checking

Camshaft Position (CMP) Sensor-G40-, Checking







Special tools and equipment
- VAG1526A or Fluke 83 Multimeter
- VAG1527B Voltage tester
- VAG1594A Connector test kit
- VAG1598/31 Test box

The Camshaft Position (CMP) sensor provides the ignition position for cylinder 1.

If a failure occurs, the knock control is switched off and the ignition angle is retarded slightly since a cylinder allocation is no longer possible. In addition, the boost pressure of the turbocharger is decreased.

The engine will continue to run without the Camshaft Position (CMP) sensor signal and can also be restarted:
- When a malfunction is recognized, the Engine Control Module (ECM) initiates one ignition spark per cylinder for each crankshaft rotation.
- The offset of one engine rotation will have no noticeable effect on the injection. Instead of occurring with intake valves open, injection will be "pre-loaded" (in front of closed intake valve). This has only a minor effect on the quality of the mixture preparation.

Checking activation
- If installed, slide rubber grommet on connector for Camshaft Position (CMP) sensor back, but leave connector connected.







- Connect VAG1527B voltage tester between sockets -2- (CMP sensor signal) and -1- (B+).

NOTE: Connector sockets are numbered respectively on the rear side of the connector.

- Operate starter for a few seconds.
- LED must blink

NOTE: Voltage testers do not go out completely during low current pick-up between activations by the ECM, but rather continue to glow a little and then get significantly brighter during activation.

If LED does not blink:
- Check voltage supply.

Checking voltage supply
- Disconnect connector at Camshaft Position (CMP) sensor.







- Connect multimeter for voltage measurement as follows:

Harness connector Terminal Measure to
1 Engine Ground (GND)

- Switch ignition on.
- Specified value: about 5 V

Checking signal wire
- Connect multimeter for voltage measurement as follows:

Harness connector Terminal Measure to
2 Engine Ground (GND)

- Switch ignition on.
- Specified value: approx. battery voltage

Checking Ground (GND) wire







- Check following wiring connection for open circuit and short circuit to B+:

Harness connector Terminal Measure to
3 Engine Ground (GND)

- Repair open circuit in wiring or short circuit if necessary.

If all specified values are being reached and the LED does not blink (measured between terminals -1- and -2- with starter and connector connected):
- Replace Camshaft Position (CMP) sensor.

If specified values are not obtained:
- Check wiring connections between CMP sensor and ECM:

Checking wiring connections
- Connect VAG1598/31 test box at wiring harness to Engine Control Module (ECM) but do not connect ECM. Scan Tool Testing and Procedures







- Check following wiring connections for open circuit and short circuit to Ground (GND) and B+:

Harness connector Terminal VAG1598/31 test box Socket
1 (B+) 98
2 (signal) 86
3 (Ground) 108

- Repair open circuit in wiring or short circuit if necessary.
- If, after erasing DTC memory, a DTC relating to CMP sensor is indicated again, even though all previous tests were OK, following malfunction is possible:
- Shutter wheel for CMP sensor is not aligned properly

- Unscrew CMP sensor and check whether shutter wheel is mounted properly at camshaft (if mounted improperly, locking lug will get squished when mounting bolt is tightened).
- If position of shutter wheel is OK, check application of crankshaft/camshaft.