Manifold Pressure/Vacuum Sensor: Testing and Inspection
NOTE: The altitude or BAROmetric pressure sensor is located in the Diesel direct injection system ECM. The Manifold Absolute Pressure sensor is a separate component and is located together with the Intake Air Temperature sensor in a housing on the air intake pipe.
Special tools, workshop equipment, testers, measuring instruments and auxiliary items required
- VAG 1551/1552 Scan Tool using VAG 1551/3 adaptor cable
Test sequence
- Connect VAG 1551/1552 Scan Tool. Testing and Inspection
- Ensure that ignition is switched ON
- 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
Rapid measuring value block HELP
Input display group number xxx
- Press 0, 1 and 0 buttons to select "Display group 10"
- Press Q button to enter input
- Compare display zone 2 (BARO sensor F96) with display zone 3 (Manifold Absolute Pressure sensor G71)
Read measuring value block 10
0 mg/H 1027 mbar 1013 mbar 0.0%
- Specification: both pressures must be the same (tolerance ± 30 mbar)
NOTE: Use the VAG 1397A turbocharger test tool to establish an independent reference value. Set the tool to test range 1 (absolute pressure). NOTE that an accurately calibrated barometer can also be used.
If value in display zone 3 deviates:
- Press -> button.
- Press 0 and 6 buttons to select Function 06: "End transfer"
- Press Q button to enter input
- Switch OFF ignition.
- 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
If value in display zone 3 deviates:
- Press -> button.
- Press 0 and 6 buttons to select Function 06: "End transfer"
- Press Q button to enter input
- Start engine
- Press 0 and 8 buttons to select Function 08: "Read measuring value block"
- Press Q button to enter input
- Press 0,1 and 0 buttons to select "Display group 10"
- Press Q button to enter input
- Disconnect Engine speed sensor harness connector. Service and Repair
- Observe the value in display field 3
(Manifold Absolute Pressure sensor)
- Value must drop consistently and then equate to the BARO sensor displayed value (display field 21)
Read measuring value block 10 ->
515 mg/H 1009mbar 1009 mbar 0.0 %
If specification obtained
- Replace Manifold Absolute Pressure sensor assembly which also includes the Intake Air Temperature sensor
- Display Readiness code. Testing and Inspection
If DTC memory has been erased
- Create Readiness code. Testing and Inspection
If specification not obtained
- Press -> button.
- Press 0 and 6 buttons to select Function 06: "End transfer"
- Press Q button to enter input
- Switch OFF ignition.
- 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 33
- Terminal 2 + socket 17
- Wire resistance: max. 1.5 Ohms
- Check wires for short to one another, to vehicle Ground and 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