Displacement Sensor and Quantity Adjuster, Checking

Modulating Piston Displacement Sensor and Quantity Adjuster, Checking

NOTE: The N746 Quantity adjuster is an electro-magnetic swivelling positioner which is controlled by the ECM via duty cycle (on- off ratio). The eccentric shaft on the Quantity adjuster moves the modulating piston on the high pressure piston thereby regulating the quantity of fuel injected.

The Modulating piston displacement sensor informs the ECM of the position of Quantity adjuster N 146 thereby determining the quantity of fuel to inject.

Special tools, workshop equipment, testers, measuring instruments and auxiliary items required
- VAG 1551/1552 Scan Tool using VAG 1551/3 adaptor cable
- VAG 1598/22 Test Box
- Fluke 83 multimeter
- VW 1594 Adaptor kit
- Wiring diagram

Test sequence

- Connect VAG 1551/1552 Scan Tool. Testing and Inspection
- Start engine and let idle
- Press 0 and 1 buttons to select Address word 01: "Engine electronics"

Display will appear as shown

Rapid data transfer HELP
Select function XX

- Press 0 and 8 buttons to select Function 08: "Read measuring value block"
- Press Q button to enter input

Display will appear as shown

Read measuring value block HELP
Input display group number XXX

- Press 0, 0 and 1 buttons to select "Display group 1"
- Press Q button to enter input

Display will appear as shown

Read measuring value block 1 ->
840 rpm 6.5 mg/H 1.480 V 87.3 °C

- Check Engine Coolant Temperature in display zone 4.
- Specification: at least 85 °C, continue with check ONLY when specification is attained.
- Check values in display zone 3
(Voltage supply from modulating piston displacement)
- Specified value: 1.250 to 1.980 Volts

Read measuring value block 1 ->
840 rpm 6.5 mg/H 1.480 V 873 °C

If specification not obtained
- Check Modulating piston displacement sensor and Quantity adjuster as described in following steps:

Modulating piston displacement sensor G149, checking

- Press -> button.
- Press 0 and 6 buttons to select Function 06: "End transfer"
- Press Q button to enter input
- Switch OFF ignition.
- Disconnect 10-pin Fuel temperature sensor harness connector

- connection to injection pump metering control
- Measure resistance between connector terminals 1 + 2 and 2 + 3
- Specified value 4.9 to 75 Ohms

If specification not obtained
- Replace injection pump. Service and Repair
- Display Readiness code. Testing and Inspection

If DTC memory has been erased
- Create Readiness code. Testing and Inspection

If specification obtained
- Connect VAG 1598/22 Test Box to ECM wiring harness.

- Check wiring for open circuit between Test Box and harness connector using Wiring diagram.
- Terminal 1 + socket 56
- Terminal 2 + socket 57
- Terminal 3 + socket 64
- Wire resistance: max. 1.5 Ohms

- Check wires for short to one another, to vehicle Ground and to battery Plus.
- Specification: Infinity Ohms

If wiring OK
- Replace Diesel direct injection system ECM J248.
- Display Readiness code. Testing and Inspection

If DTC memory has been erased
- Create Readiness code. Testing and Inspection

Checking Quantity adjuster (N146)

- Press -> button.
- Press 0 and 6 buttons to select Function 06: "End transfer"
- Press Q button to enter input
- Switch OFF ignition.
- Disconnect connector for Quantity adjuster
(connector to injection pump Quantity adjuster).

- Measure resistance between connector terminals 5 + 6.
- Specification: 0.5 to 2.5 Ohms

If specification not obtained, replace injection pump. Service and Repair
- Display Readiness code. Testing and Inspection

If DTC memory has been erased
- Create Readiness code. Testing and Inspection

If specification obtained
- Connect VAG 1598/22 Test Box to ECM wiring harness.

- Check wiring for open circuit between Test Box and harness connector using Wiring diagram.
- Terminal 5 + sockets 2 and 28
- Terminal 6 + sockets 59,66 and 80
- Wire resistance: max. 1.5 Ohms