Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
Camshaft Position (CMP) Sensors, checking
This procedure is used to check Camshaft Position (CMP) Sensors G40 and G163.
Special tools, testers and auxiliary items required
- Multimeter V.A.G 1526 A or equivalent.
- Voltage Tester VAG1527B or equivalent.
- Adapter Cable (121-Point) VAG1598/31.
- Connector Test Set VAG1594C.
Test requirements
- Ignition switched off.
Procedure
- Remove front engine cover - arrows -1- and -2 -.
- Remove rear engine cover - arrows -.
- Disconnect relevant Camshaft Position (CMP) Sensor electrical harness connector.
Cylinder bank 1 (right):
- Remove fuel hose - 1 -.
- Disconnect electrical connector - 2 - from Mass Air Flow (MAF) Sensor G70.
- Remove Mass Air Flow (MAF) Sensor G70 from air duct hose - 3 -.
- Remove upper part of air filter housing with Mass Air Flow (MAF) Sensor G70 - arrows -.
- Remove resonator - 1 - in direction of - arrow - from air duct hose.
- Disconnect brake booster vacuum hose - 1 - at bulkhead.
- Loosen clamp - 3 - and remove air duct hose - 2 -.
- Disconnect electrical harness connector - arrow - from Camshaft Position (CMP) Sensor G40 at rear of right cylinder head.
Cylinder bank 2 (left):
- Remove screw - arrow - retaining coolant reservoir.
- Disconnect electrical connector from Engine Coolant Level (ECL) Warning Switch F66 at bottom of coolant reservoir and set aside the coolant reservoir with coolant hoses - 1 - and - 2 - connected.
- Disconnect electrical harness connector - arrow - from Camshaft Position (CMP) Sensor 2 G163 at rear of the left cylinder head.
Checking activation
- Using Voltage Tester VAG1527B or equivalent, and a probe from Connector Test Set VAG1594C. Connect Camshaft position (CMP) sensor electrical harness connector terminals 1 and 2 together and check for voltage leaving Camshaft position (CMP) sensor electrical harness connector connected to Camshaft position (CMP) sensor.
- Operate starter for a few seconds.
LED must blink.
- 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.
- Switch ignition off.
If LED blinks:
- Replace faulty Camshaft Position (CMP) Sensor.
If LED does not blink:
Checking voltage supply
- Using Multimeter V.A.G 1526 A or equivalent, check the following wiring connection for voltage:
| Harness connector Terminal | Measure to |
|---|---|
| 1 | Engine Ground (GND) |
- Switch ignition on.
Specified value: about 5 V.
- Switch ignition off.
Checking signal wire
- Using Multimeter V.A.G 1526 A or equivalent, check the following wiring connection for voltage:
| Harness connector Terminal | Measure to |
|---|---|
| 2 | Engine Ground (GND) |
- Switch ignition on.
Specified value: approx. battery voltage.
- Switch ignition off.
Checking Ground (GND)
- Using Multimeter V.A.G 1526 A or equivalent, check the following wiring connection for voltage:
| Harness connector Terminal | Measure to |
|---|---|
| 3 | Battery positive (+) |
Specified value: about 10 V.
If specification is not obtained:
- Check wiring for a short circuit to Battery positive (+) or an open circuit.
- If necessary, repair the wiring connection.
If no malfunction can be found:
Checking wire connections between Camshaft Position (CMP) sensor and Engine Control Module (ECM)
- Connect Adapter Cable (121-Point) VAG1598/31 to wiring harness of Engine Control Module (ECM) J623 ; the ECM is not connected. → Diagnostic tester, connecting .
- Using Adapter Cable (121-Point) VAG1598/31 and Multimeter V.A.G 1526 A or equivalent, check the following wiring connections for an open circuit.
- Camshaft Position (CMP) Sensor G40 (bank 1).
| Harness connector Terminal | Test box Socket |
|---|---|
| 1 Battery positive (+) | 98 |
| 2 (signal) | 87 |
| 3 Ground (GND) | 108 |
- Camshaft Position (CMP) Sensor 2 G163 (bank 2).
| Harness connector Terminal | Test box Socket |
|---|---|
| 1 Battery positive (+) | 98 |
| 2 (signal) | 86 |
| 3 Ground (GND) | 108 |
Specified value: Wire resistance max 1.5 Ω.
If specification is not obtained:
- Check wiring for a short circuit to Battery positive (+) or an open circuit.
- If necessary, repair wiring connection.
If no malfunction can be found:
- Replace Engine Control Module (ECM) J623. → Engine Control Module (ECM) J623, replacing .
Assembly is performed in reverse order of removal. Note the following:
Final procedures
After repair work, the following work steps must be performed in the mentioned sequence:
- Check DTC memory..
- If necessary, erase DTC memory..
- If DTC memory was erased, generate readiness code..
- End diagnosis and switch ignition off.
NO RELATED
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.