Camshaft Position (CMP) Sensor -G40-, Checking

Camshaft Position (CMP) Sensor -G40-, Testing







Special tools and equipment
- VAG 1526 A
- VAG1527 B
- VAG 1594 A
- VAG 1598/31

The Hall sender indicates the ignition position for Cylinder 1.

If the Hall sender fails to function, the knock control is switched off and the ignition timing is retarded slightly because the signals can no longer be assigned to the cylinders. In addition the charge pressure of the turbocharger is reduced.

Even without a signal from the Hall sender the engine will continue to run and can also be re-started.

- When a malfunction is detected the engine control module produces one spark per crankshaft revolution for each cylinder.
- The fact that the injection system is one revolution out of phase does not have any noticeable effect on the fuel injection. If this happens, the fuel is injected upstream of the closed inlet valve instead of while the inlet valve is open. This has only a minor influence on the quality of the air/fuel mixture.

Checking activation
- Slide back rubber sleeve (if installed) on connector for Hall sender but leave connector plugged in.







- Connect VAG 1527 B voltage tester between contact 2 (Hall sender signal) and contact 1 (positive).

NOTE: The connector contacts are numbered on the back of the connector.

- Operate starter for a few seconds.
- LED should flash

NOTE: The LEDs on voltage testers with a low current draw continue to glow faintly between impulses from the engine control module (rather than going out completely) and become much brighter when receiving an impulse.

If the LED does not flash:

Checking voltage supply
- Unplug connector from Hall sender.







- Connect multimeter (voltage measurement range) as follows:

Connector Contact Measure against
1 Engine Ground

- Switch on ignition.

- Specification: approx. 5 V

Testing signal wire
- Connect multimeter (voltage measurement range) as follows:

Connector Contact Measure against
2 Engine Ground

- Switch on ignition.

- Specification: approx. battery voltage

Testing Ground wire







- Test for open circuit and short to positive in the following wiring connection:

Connector Contact Measure against
3 Engine Ground

- Correct any open/short circuit as necessary.

If all the readouts match the specifications but the LED does not flash (measurement taken between contacts 1 and 2 without unplugging connector and while operating starter):
- Replace the Hall sender.

If the specifications are not obtained:

Testing wiring between Hall sender and engine control module
- Connect test box VAG 1598/31 to wiring harness for engine control module. Do not connect to the engine control module itself.







- Test for open circuit and short to positive or Ground in the following wiring connections

Connector Contact Test box VAG 1598/31 Socket
1 (positive) 98
2 (signal) 86
3 (Ground) 108

- Correct any open/short circuit as necessary.
- If all the test results so far have been OK but a fault relating to the camshaft position (CMP) sensor (Hall sender) is displayed again after erasing the Diagnostic Trouble Code (DTC) memory as a test measure, the cause may be as follows:
- Rotor ring on CMP sensor out of position

- Unbolt CMP sensor, then check to ensure that the rotor ring is correctly aligned on the camshaft. If incorrectly installed, the catch will be pressed flat when the securing screw is tightened.
- If the rotor ring is correctly aligned, check the position of the camshaft in relation to the crankshaft.