Exhaust Gas Recirculation (EGR), checking

Special tools, testers and auxiliary items required 

• Portable multimeter V.A.G 1526B
• Connector test set V.A.G 1594C
• Test box 1598/22
• Test box 1598/31

not pictured

Special tools, testers and auxiliary items required 

• Scan tool V.A.G 1551 or mobile scan tool V.A.G 1552 with cable V.A.G 1551/3C
• Wiring diagram

Test sequence 

Testing the EGR system is done in function 04 (Basic setting). This procedure activates the EGR valve every 10 seconds to make it possible to read the extreme values for EGR (Mass Air Flow MAF Sensor) in display field 3.

• Connect scan tool V.A.G 1551 or mobile scan tool V.A.G 1552 with cable V.A.G 1551/3C and select control module for engine electronics with the "address word" 01. Engine must run at idle during this: Refer to 01 ON BOARD DIAGNOSTIC (OBD) from M.Y. 99-01 or 01 ON BOARD DIAGNOSTIC (OBD) from M.Y. 2002 and on

Scan tool display:

Quick data transfer HELP Select function XX

• Press buttons 0 and 4 for the function "Initiate basic setting" and press Q button to confirm input.

Scan tool display:

Basic setting HELP Enter display group number XXX

• Press buttons 0 0 and 3 for the "Display group number 3" and press Q button to confirm input.

Scan tool display: (1 to 4 = Display fields)

System in basic setting 3 -> 900/min EGR not active 500 mg/H 0%

Display field 2 must switch between EGR active and EGR not active every 10 seconds.

Display field 3 and 4 must move in the following control range:

EGR not active

• Specified value in display field 3: 400 to 580 mg/H
• Specified value in display field 4: 0 to 5%

EGR active

• Specified value in display field 3: 150 to 340 mg/H
• Specified value in display field 4: 95 to 100%

If specifications are not obtained:

• Check mechanical EGR valve. Refer to Exhaust Gas Recirculation (EGR) valve, checking  .
• Check vacuum hoses. Refer to Vacuum hose connections, diagram  .
• Check EGR Vacuum Regulator Solenoid Valve N18 as follows:
• Press → button

• Press buttons 0 and 6 for the function "End data transfer" and press Q button to confirm input.
• Switch ignition off.

• Disconnect connector - 1  - from EGR Vacuum Regulator Solenoid Valve N18 - 2  -.
• Measure resistance at valve. Specification: 14 to 20 Ω

If specification is not obtained:

• Replace the EGR Vacuum Regulator Solenoid Valve N18.

If specification is obtained:

• Switch ignition on.

• Measure voltage supply of valve at connector - terminal 1  - and at engine Ground (GND). Specification: approx. battery voltage

If specification is not obtained:

• Switch ignition off.

Vehicles with 80-pin control module 

• Connect test box 1598/22 to control module wiring harness.

• Check for open circuits in wires between test box and harness connector according to wiring diagram. - Terminal 1 + socket 2 + 28  - and - terminal 2 + socket 29  - wiring resistance: max. 1.5 Ω
• Check wires for short circuit to each other, to vehicle Ground (GND) and to B+. Specification: ∞ Ω

Vehicles with 121-pin control module 

• Connect test box 1598/31 to control module wiring harness.

• Check for open circuits in wires between test box and connector according to wiring diagram. Terminal 1 + socket 1 and terminal 2 + socket 61 wiring resistance: max. 1.5 Ω
• Check wires for short circuit to each other, to vehicle Ground (GND) and to B+. Specification: ∞ Ω

If no malfunction is detected in the wiring:

• Replace Diesel Direct Fuel Injection (DFI) Engine Control Module (ECM) J248. Refer to 23 DIESEL FUEL INJECTION for M.Y. 99-01, or 23 DIESEL FUEL INJECTION from M.Y. 2002 and on