With Manufacturer's Scan Tool

Camshaft Position (CMP) Sensor -G40-, Checking

Special tools and equipment







- VAG1526A
- VAG1527B
- VAG1594A
- VAG1598/31

The Camshaft Position (CMP) sensor -G40- indicates ignition position for cylinder 1.

If Camshaft Position (CMP) sensor -G40- fails to function, the knock recognition control is switched off and ignition timing is retarded slightly because signals can no longer be assigned to cylinders. Furthermore, the charge pressure of turbocharger is lowered.

Engine will continue to run without Camshaft Position (CMP) sensor -G40-, and can also be restarted.

- When a malfunction is recognized, 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 injection quality. Instead of occurring with intake valves open, injected fuel 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 back rubber boot on connector for Camshaft Position (CMP) sensor, but leave connector connected.







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

NOTE: Connector socket numbers are shown on rear side of 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 ECM, but rather continue to glow a little and then get significantly brighter during activation.

If LED does not blink:

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







- Connect multimeter for voltage measurement as follows:

Harness connector Measure to
Terminal
1 Engine Ground (GND)

- Switch ignition on.
- Specification: about 5 V

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

Harness connector Measure to
Terminal
2 Engine Ground (GND)

- Switch ignition on.
- Specification: approx. battery voltage

Checking Ground (GND) wire







- Check for open circuit, short to positive, or short to ground in following wiring connections:

Harness connector Measure to
Terminal
3 Engine Ground (GND)

- Repair any open/short circuit as necessary.

If specified values are all obtained and LED does not blink with connector connected (measured between terminals 1 and 2 with engine turning or when engine is being cranked by starter):
- Replace Camshaft Position (CMP) sensor.

If specified values are not obtained:

Checking wire connections between Camshaft Position (CMP) sensor and Engine Control Module (ECM)
- Connect VAG1598/31 test box at wiring harness to ECM, do not connect ECM. Electrical Testing Using VAG1598/31 Test Box







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

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

- Repair open circuit or short circuit if necessary.
- If, after erasing DTC memory for the sake of the test, a DTC relating to the Camshaft Position (CMP) sensor (hall sensor) is indicated again, even though all previous tests were OK, the following malfunction is possible:
- Shutter wheel for Camshaft Position (CMP) sensor is not aligned properly.
- Unscrew Camshaft Position (CMP) sensor and check whether shutter wheel is mounted properly at camshaft (if mounted improperly, locking tab will get squished when mounting bolt is tightened).
- If position of shutter wheel is OK, check orientation of crankshaft to camshaft.