Exhaust Gas Recirculation (EGR) and Mass Air Flow (MAF) sensor functions, checking: Checking

WARNING: This page is about a different car, the 1999 Volkswagen Jetta, 1998 Volkswagen Jetta, and 1997 Volkswagen Jetta. However, it is still accessible from the selected car via links, so may be relevant.

Connect VAG1551 or VAG1552 scan tool.
1. See VAG1551 SCAN TOOL (ST), CONNECTING
Start engine and let idle.
Press buttons -0- and -1- to insert "Engine Electronics" address word 01.

Indicated on display

Fig 1: Scan Tool Display - Checking Exhaust Gas Recirculation (EGR) And Mass Air Flow (MAF) Sensor Functions (1 Of 6)

Press buttons -0- and -3- to select "Output Diagnostic Test Mode" function 03.
Press -Q- button to confirm input.

Indicated on display

Fig 2: Scan Tool Display - Checking Exhaust Gas Recirculation (EGR) And Mass Air Flow (MAF) Sensor Functions (2 Of 6)

NOTE: Individual DTM components are activated for 30 seconds. Various work sequences must be carried out with the scan tool within this period as well as reading the displayed values. Read over the following work sequence first to familiarize yourself with the procedure.

Indicated on display

Fig 3: Scan Tool Display - Checking Exhaust Gas Recirculation (EGR) And Mass Air Flow (MAF) Sensor Functions (3 Of 6)

Press --> button.

Indicated on display

Fig 4: Scan Tool Display - Checking Exhaust Gas Recirculation (EGR) And Mass Air Flow (MAF) Sensor Functions (4 Of 6)

Press -C- button.
Press buttons -0- and -8- to select "Read Measuring Value Block" function 08.
Press -Q- button to confirm input.

Indicated on display

Fig 5: Scan Tool Display - Checking Exhaust Gas Recirculation (EGR) And Mass Air Flow (MAF) Sensor Functions (5 Of 6)

Press buttons -0-, -0- and -3- to input display group no. 3 (003).
Press -Q- button to confirm input.
Indicated on display

Fig 6: Scan Tool Display - Checking Exhaust Gas Recirculation (EGR) And Mass Air Flow (MAF) Sensor Functions (6 Of 6)

NOTE: The values in display fields 3 and 4 must fluctuate within the following control range:

Specification display field 3:
Lower range: 230 -310 mg/stroke
Upper range: 360 -480 mg/stroke
Specification display field 4:
Lower range: 2 to 5%
Upper range: 90 to 95%

NOTE: Due to the slow refresh rate of the VAG1551 scan tool, the displayed values can greatly vary. Ensure that the upper and lower range values in display fields 3 and 4 are obtained. Only regard the minimum or maximum values!

If specifications not obtained

Check Mass Air Flow sensor and EGR valve voltage supply as follows.
Press --> button.
Press buttons -0- and -6- to select "End Output" function 06.
Press -Q- button to confirm input.
Switch ignition off.
Disconnect harness connector -1- from Mass Air Flow sensor -2-

Fig 7: Disconnecting Harness Connector From Mass Air Flow Sensor

Switch ignition on.
Select 20 Volt measurement range

Perform voltage measurement using multimeter between following connector terminals

MASS AIRFLOW SENSOR CONNECTOR (G70) VOLTAGE SPECIFICATIONS

Connector on terminal -G70-	Specification (Ignition On)
3 and Ground	Battery voltage (approx)
3 and 5	Battery voltage (approx)
1 and Ground	Approx. 5 Volts
1 and 5	Approx. 5 Volts

Fig 8: Identifying Mass Air Flow Sensor Harness Connector Terminals

If specifications not obtained

Switch ignition off.
Connect VAG1598/18 test box to Diesel DFI ECM connector.

Fig 9: Connecting VAG1598/18 Test Box To Diesel DFI ECM Connector
Check wiring for open circuit between test box and harness connector, using wiring diagrams:
- Terminal 1 and test box socket 19
- Terminal 2 and test box socket 33
- Terminal 3 and test box socket 23
- Terminal 5 and test box socket 1
- Terminal 6 and test box socket 13
- Wire resistance: max. 1.5 ohms (ohm)
Check wiring for short circuit between connector terminals.
Specification: INFINITY ohm (no continuity)

If specifications obtained:

Check EGR vacuum regulator solenoid valve N18 as follows:
Disconnect N18 valve harness connector.
See item 2
Switch multimeter to resistance range.

Connect multimeter between valve terminals and measure resistance

Fig 10: Measuring Resistance Of EGR Vacuum Regulator Solenoid Valve

Specification: 14 to 18 ohms

If specification not obtained:

Replace EGR vacuum regulator solenoid valve -N18-
1. See item 2
Display readiness code, see READINESS CODE, DISPLAYING .

If DTC memory was erased:

Create readiness code again, see READINESS CODE, SETTING (UP TO M.Y. 1997) .

If specification obtained:

Switch ignition on.
Connect multimeter between connector terminal 1 and engine Ground using adapters from VW1594 connector test kit.
Specification: approx. battery voltage

If specification not obtained:

Switch ignition off.

Fig 11: Identifying EGR Vacuum Regulator Solenoid Valve Harness Connector Terminals

Check wiring for open circuit/short to positive or negative between test box and connector using wiring diagrams.
- Terminal 1 and test box socket 68
- Terminal 2 and test box socket 25
- Wire resistance: max. 1.5 ohms (ohm)
Check wiring for short circuit between connector terminals.
Specification: INFINITY ohm (no continuity)

If wiring is OK:

Replace Diesel DFI ECM -J248-, see item 3 .
Display readiness code, see READINESS CODE, DISPLAYING .

If DTC memory was erased:

Create readiness code again, see READINESS CODE, SETTING (UP TO M.Y. 1997) .