Volkswagen New Beetle. Manual - part 1786

Possible Effects

Possible effects are no glow plug operation and/or engine runs rough when cold.

Test Requirements

Fuses must be okay. Ensure battery voltage is at least 11.5 volts, glow plug fuse strip is okay, glow plug relay is
operating properly. A/C and all electrical accessories must be switched off. Alternator must be okay. Engine
must be cold.

Test Procedures

1. Check glow plug relay using Output Diagnostic Test Mode. See OUTPUT DIAGNOSTIC TEST

MODE and COMPONENT LOCATIONS .

2. If glow plug relay is okay, go to next step. If glow plug relay is not okay, replace as necessary. Erase

DTC memory. See CLEARING DIAGNOSTIC TROUBLE CODES (FUNCTION 05) under SELF
DIAGNOSTIC SYSTEM. Verify repair. Test is complete. Perform ECM relearn procedure. See TEST
DRIVE RELEARN PROCEDURE .

Disconnect engine coolant temperature sensor harness connector. Disconnect glow plug harness
connectors. Turn ignition on. Measure voltage between ground and each glow plug harness connector.
Voltage should be at least 11.5 volts for approximately 20 seconds after ignition switch is turned on. If
voltage is as specified, go to next step. If voltage is not as specified, repair open or short in wiring
between glow plugs and glow plug relay. After repairs, erase DTC memory. See CLEARING
DIAGNOSTIC TROUBLE CODES (FUNCTION 05) under SELF DIAGNOSTIC SYSTEM. Verify
repair. Test is complete. Perform ECM relearn procedure. See TEST DRIVE RELEARN
PROCEDURE .

4. Turn ignition off. Using a test light connected to positive battery terminal, touch each glow plug terminal

(component side). If test light illuminates, problem is intermittent. If test light does not illuminate, replace
appropriate glow plug(s).

5. After repairs, erase DTC memory. See CLEARING DIAGNOSTIC TROUBLE CODES

(FUNCTION 05) under SELF DIAGNOSTIC SYSTEM. Verify repair. Test is complete. Perform ECM
relearn procedure. See TEST DRIVE RELEARN PROCEDURE .

NOTE:

For connector terminal wire colors, see appropriate WIRING DIAGRAM under
ENGINE PERFORMANCE in SYSTEM WIRING DIAGRAMS. For component
locations, see COMPONENT LOCATIONS .

NOTE:

Before replacing any component, ensure all connectors at component and ECM
are clean and tight. After making any repairs, disconnect ECM harness
connector for 10 seconds, connect ECM harness connector and retest system.
It is necessary to generate an ECM readiness code if ECM memory is cleared,
battery voltage is disconnected or ECM is disconnected.

NOTE:

Disconnecting engine coolant temperature sensor simulates cold engine.

2003 Volkswagen New Beetle GLS

2002-2004 ENGINE PERFORMANCE Self-Diagnostics - 1.9L Turbo Diesel - Beetle, Golf & Jetta (Engine Code ALH)

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DTC P0401/16785, DTC P0402/16786, DTC P1402/17810 & DTC P1441/17849

Code Definition

DTC P0401/16785
EGR Vacuum Regulator Solenoid Valve (N18) - Gas Flow Too Low - Short To B+

DTC P0402/16786
EGR Vacuum Regulator Solenoid Valve (N18) - Gas Flow Too High - Short To B+

DTC P1402/17810
EGR Vacuum Regulator Solenoid Valve (N18) - Short To B+

DTC P1441/17849
EGR Vacuum Regulator Solenoid Valve (N18) - Open Circuit/Short To Ground

Possible Effects

Possible effects are poor idle black smoke and/or EGR system malfunction.

Test Procedures

1. Use Output Diagnostic Test Mode to check Exhaust Gas Regulator Valve (N18). See OUTPUT

DIAGNOSTIC TEST MODE .

2. If valve does not click, go to next step. If valve clicks, erase DTC memory. See CLEARING

DIAGNOSTIC TROUBLE CODES (FUNCTION 05) under SELF DIAGNOSTIC SYSTEM. Perform
ECM relearn procedure. See TEST DRIVE RELEARN PROCEDURE . If no DTC resets, test is
complete.

NOTE:

For connector terminal wire colors, see appropriate WIRING DIAGRAM under
ENGINE PERFORMANCE in SYSTEM WIRING DIAGRAMS. For component
locations, see COMPONENT LOCATIONS .

NOTE:

EGR Vacuum Regulator Solenoid Valve (N18), with condition short to ground
may give to much EGR; open circuit or short to B+ will not.

NOTE:

When using scan tool in Output Diagnostic Test Mode (DTM) to activate engine
components, some components may be barely audible. Check component by
touch or use mechanics stethoscope if necessary.

2003 Volkswagen New Beetle GLS

2002-2004 ENGINE PERFORMANCE Self-Diagnostics - 1.9L Turbo Diesel - Beetle, Golf & Jetta (Engine Code ALH)

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3. Turn ignition off. Disconnect EGR vacuum regulator solenoid valve harness connector. See

COMPONENT LOCATIONS .

4. Measure resistance between terminals No. 1 and 2 at EGR vacuum regulator solenoid valve (component

side). Resistance should be 14-20 ohms. If resistance is as specified, go to next step. If resistance is not as
specified, replace EGR vacuum regulator solenoid valve. After repairs, erase DTC memory. See
CLEARING DIAGNOSTIC TROUBLE CODES (FUNCTION 05) under SELF DIAGNOSTIC
SYSTEM. Verify repair. Test is complete. Perform ECM relearn procedure. See TEST DRIVE
RELEARN PROCEDURE .

5. Turn ignition on. Measure voltage between ground and terminal No. 1 at EGR valve harness connector,

see COMPONENT LOCATIONS and Fig. 30 . Voltage should be at least 11.5 volts. If voltage is as
specified, go to next step. If voltage is not as specified, repair open in wiring between EGR vacuum
regulator solenoid valve and fuse box. After repairs, erase DTC memory. See CLEARING
DIAGNOSTIC TROUBLE CODES (FUNCTION 05) under SELF DIAGNOSTIC SYSTEM. Verify
repair. Test is complete. Perform ECM relearn procedure. See TEST DRIVE RELEARN
PROCEDURE .

6. Turn ignition off. Disconnect ECM harness connector. Connect VAG 1598/31 test box to ECM harness

connector. See CONNECTING VAG TEST BOX (leave ECM disconnected).

Measure resistance between terminal No. 1 at EGR valve harness connector and socket No. 1 at test box.
See Fig. 30 . Measure resistance between terminal No. 1 at EGR valve harness connector and socket No.
2 at test box. Measure resistance between terminal No. 2 at EGR valve harness connector and socket No.
61 at test box. Resistance should be less than 1.5 ohms for each reading. If resistance is as specified, go to
next step. If any resistance is not as specified, repair open in wiring between 2 pin EGR valve harness
connector and ECM. After repairs, erase DTC memory. See CLEARING DIAGNOSTIC TROUBLE
CODES (FUNCTION 05) under SELF DIAGNOSTIC SYSTEM. Verify repair. Test is complete.
Perform ECM relearn procedure. See TEST DRIVE RELEARN PROCEDURE .

8. Check 2 pin EGR valve harness connector terminals No. 1 and 2 short to one and other. Check terminals

No. 1 and 2 for short to B+. Check terminals No. 1 and 2 for short to ground. If wiring is okay, go to next
step. If wiring is not okay, repair short circuit(s) as necessary. After repairs, erase DTC memory. See
CLEARING DIAGNOSTIC TROUBLE CODES (FUNCTION 05) under SELF DIAGNOSTIC
SYSTEM. Verify repair. Test is complete. Perform ECM relearn procedure. See TEST DRIVE
RELEARN PROCEDURE .

9. If all wiring is okay and voltage is okay at 2 pin EGR valve harness connector terminal No. 1. See 5 .

Replace faulty ECM. After repairs, erase DTC memory. See CLEARING DIAGNOSTIC TROUBLE
CODES (FUNCTION 05) under SELF DIAGNOSTIC SYSTEM. Verify repair. Test is complete.
Perform ECM relearn procedure. See TEST DRIVE RELEARN PROCEDURE .

DTC P0501/16885 & DTC P1540/17948

Code Definition

DTC P0501/16885
Vehicle Speed Sensor (VSS) - Implausible Signal

NOTE:

Test box socket numbers correspond to ECM pin numbers.

2003 Volkswagen New Beetle GLS

2002-2004 ENGINE PERFORMANCE Self-Diagnostics - 1.9L Turbo Diesel - Beetle, Golf & Jetta (Engine Code ALH)

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DTC P1540/17948
Vehicle Speed Signal (VSS) - Signal To High

Possible Effects

Possible effects are speedometer does not operate, cruise control system does not operate, vehicle bucks during
shifting and A/C system may not operate.

Test Procedures

1. Check speedometer operation. If speedometer operates properly, go to next step. If speedometer does not

operate properly, repair speedometer as necessary.

2. Turn ignition off. Disconnect Engine Control Module (ECM) harness connector. Connect VAG 1598/31

test box to ECM harness connector. Leave ECM disconnected. See CONNECTING VAG TEST BOX .

Raise and support left front of vehicle. Connect a diode test light between sockets No. 4 and 20 at test
box. See Fig. 25 and Fig. 26 .

4. Turn ignition on, with engine off. Rotate left front wheel while observing test light. If test light blinks,

VSS signal is okay. If test light does not blink, check wiring from VSS and between instrument cluster
and ECM for open or short circuits. If wiring is okay go to next step. If wiring is not okay. Repair as
necessary. After repairs, erase DTC memory. See CLEARING DIAGNOSTIC TROUBLE CODES
(FUNCTION 05) under SELF DIAGNOSTIC SYSTEM. Verify repair. Test is complete. Perform ECM
relearn procedure. See TEST DRIVE RELEARN PROCEDURE .

5. Check VSS. Replace if faulty. After repairs, erase DTC memory. See CLEARING DIAGNOSTIC

TROUBLE CODES (FUNCTION 05) under SELF DIAGNOSTIC SYSTEM. Verify repair. Test is
complete. Perform ECM relearn procedure. See TEST DRIVE RELEARN PROCEDURE .

NOTE:

For connector terminal wire colors, see appropriate WIRING DIAGRAM under
ENGINE PERFORMANCE in SYSTEM WIRING DIAGRAMS. For component
locations, see COMPONENT LOCATIONS .

NOTE:

Test box socket numbers correspond to ECM pin numbers.

2003 Volkswagen New Beetle GLS

2002-2004 ENGINE PERFORMANCE Self-Diagnostics - 1.9L Turbo Diesel - Beetle, Golf & Jetta (Engine Code ALH)

Helpmelearn Repair Manuals

Wednesday, December 14, 2005 8:48:22 AM

Page 59

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