sensor VOLKSWAGEN CORRADO 1990 Manual Online

F - BASIC TESTING
Article Text (p. 13)
1990 Volkswagen Corrado
For Volkswagen Technical Site: http://vw.belcom.ru
Copyright © 1998 Mitchell Repair Information Company, LLC
Thursday, March 23, 2000 09:44PM
DISTRIBUTOR
HALL EFFECT SENDER
1) Remove coil secondary and attach to ground. Disconnect
Hall Effect sender wire at the distributor. Using a LED Test Light (US
1115), check for voltage between outer terminals of connector. See
Fig. 5 or 8. With ignition on, light should be on. If not, check
wiring for short or open circuit. If wiring is okay, replace Digifant
control unit.
2) If light came on in step 1), reconnect Hall Effect sender
harness connector. Pull back Hall Effect sender boot to expose contact
terminals. Apply LED Test Light (US 1115) probe to center contact and
battery positive terminal. See Fig. 5. Observe test light while
cranking engine. If test light blinks, Hall Effect sender is okay. If
not, replace Hall Effect-sender.
IDLE SPEED, CO LEVEL & IGNITION TIMING
Ensure idle speed, CO level and base ignition timing are set
to specification. If necessary, see ON-VEHICLE ADJUSTMENTS article.
IDLE SPEED & CO LEVEL TABLEÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄApplication Idle RPM CO Level %
All Models ............ 800-1000 .............. 0.3-1.2%
ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄIGNITION TIMING TABLE (Degrees BTDC @ RPM)
ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄApplication Checking Adjusting
1.8L ............... 4-8 @ 2250-2350 . 5-7 @ 2250-2350
2.0L ................ 4-8 @ 770-830 ...... 5-7 @ 770-830
2.1L (1) ........... 4-8 @ 2250-2350 . 5-7 @ 2250-2350
(1) - With coolant temperature sensor disconnected.
ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ SUMMARY
If no faults were found while performing F - BASIC TESTING,
proceed to H - TESTS W/CODES article for diagnosis by symptom (i.e.,
ROUGH IDLE, NO START, etc.) or intermittent diagnostic procedures.
END OF ARTICLE

FUSES & CIRCUIT BREAKERS
Article Text (p. 2)
1990 Volkswagen Corrado
For Volkswagen Technical Site: http://vw.belcom.ru
Copyright © 1998 Mitchell Repair Information Company, LLC
Thursday, March 23, 2000 09:45PM
Right Tail & Side Lights
8 - 10 Amp
Left Tail & Side Lights
9 - 20 Amp
Rear Window & Mirror Heating
10 - 15 Amp
Foglights
11 - 10 Amp
Left High Beam, High Beam Indicator
12 - 10 Amp
Right High Beam
13 - 10 Amp
Horn, Radiator Fan
14 - 15 Amp
Back-Up Lights, Electric Mirrors, Heated Windshield Washer
Jets
15 - 10 Amp
Engine Electronic
16 - 15 Amp
Warning/Indicator Lights, Multi-Function Indicator, Glove Box
Light, Cassette Storage Light, Rear Spoiler
17 - 10 Amp
Turn Signals
18 - 20 Amp
Fuel Pump, Oxygen Sensor
19 - 30 Amp
Radiator Fan, Air Conditioner
20 - 10 Amp
Brakelights, Cruise Control
21 - 15 Amp
Dome & Luggage Compartment Lights, Cigarette Lighter, Central
Locking System, Multi-Function Indicator
22 - 10 Amp
Radio
CAUTIONS & WARNINGS
ELECTRICAL SHOCK
WARNING: Contact with live components of ignition system while
engine is running could lead to a fatal electric shock.
RADIATOR FAN
Keep hands away from radiator fan. Fan is controlled by a
thermostatic switch which may come on or run for up to 15 minutes even
after engine is turned off.
RADIATOR CAP
CAUTION: Always disconnect the fan motor when working near the
radiator fan. The fan is temperature controlled and could

H - TESTS W/O CODES
Article Text (p. 2)
1990 Volkswagen Corrado
For Volkswagen Technical Site: http://vw.belcom.ru
Copyright © 1998 Mitchell Repair Information Company, LLC
Thursday, March 23, 2000 09:45PM
WILL NOT START OR STARTS HARD COLD (CRANKS OKAY)
* Check ignition fuse (if equipped).
* Check fuel pump fuse and fuel pump relay.
* Verify air intake system is unrestricted.
* Ensure fuel system pressure and volume are correct.
* Check cold start valve and thermo time switch operation.
* Ensure airflow sensor plate is in rest position. Adjust as
necessary.
* Test coolant temperature sensor and wiring. Repair or replace
as required.
* Check for poor ignition ground (1.8L & 2.0L 16-valve engines).
* Check for poor quality or contaminated fuel.
* Check condensation (water) in fuel tank causing fuel pump to
freeze (cold climate).
* Check exhaust system for restriction.
* Test airflow meter. Replace if faulty.
* Ensure sufficient secondary spark is available.
* Check air induction system for cracks or restriction.
* Ensure vacuum hoses are not disconnected or damaged.
* Ensure fuel system residual pressure is correct.
* Ensure fuel injector operation is correct.
* Ensure EGR valve operation is correct and valve closes
completely (if equipped).
* Check for cracks or poor connections at throttle body.
* Ensure ignition and valve timing are correct.
* Check ignition coil primary connections and wiring harness.
* Ensure ignition coil resistance is within specification.
* Check air temperature sensor operation (if equipped).
* Ensure electrical harness and connectors are not broken or loose.
* Ensure ECU or ignition control unit has correct voltage supply
and is properly grounded.
* Ensure engine has sufficient compression.
* Inspect intake air components for leaking hoses, connections or
cracks. Repair as required.
WILL NOT START OR STARTS HARD HOT (CRANKS OKAY)
* Check ignition fuse (if equipped).
* Check fuel system fuse and fuel pump relay.
* Check for poor quality or contaminated fuel.
* Check condensation (water) in fuel tank causing fuel pump to
freeze (cold climate).
* Check exhaust system for restriction.
* Check cold start valve and thermo time switch operation.
* Check fuel system and control system pressure. Replace pressure
regulator if necessary.
* Check residual fuel pressure. Replace fuel pump check valve or
fuel accumulator as necessary.
* Check oxygen sensor system operation.
* Ensure airflow sensor plate is in rest position. Adjust as

H - TESTS W/O CODES
Article Text (p. 3)
1990 Volkswagen Corrado
For Volkswagen Technical Site: http://vw.belcom.ru
Copyright © 1998 Mitchell Repair Information Company, LLC
Thursday, March 23, 2000 09:45PM
necessary.
* Ensure injector spray patterns and volume are correct. Replace
faulty injectors.
* Inspect fuel lines and connections for leaks.
* Check carbon canister solenoid valves (CIS-E Motronic).
* Test airflow meter. Replace if faulty.
* Ensure sufficient secondary spark is available.
* Check air induction system for cracks or restriction.
* Check airflow sensor plate rest position.
* Ensure vacuum hoses are not disconnected or damaged.
* Ensure EGR valve operation is correct and valve closes
completely (if equipped).
* Check for cracks or poor connections at throttle body.
* Ensure ignition and valve timing are correct.
* Check ignition coil primary connections and wiring harness.
* Ensure ignition coil resistance is within specification.
* Check air temperature sensor operation.
* Check coolant temperature sensor operation.
* Ensure electrical harness and connectors are not broken or loose.
* Ensure ECU or ignition control unit has correct voltage supply
and is properly grounded.
* Ensure engine has sufficient compression.
ENGINE STALLS OR IDLES ROUGH
* Check fuel system and control system pressure. Replace pressure
regulator if necessary.
* Check cold start valve for leaking (engine warm).
* Ensure injector spray patterns and volume are correct. Replace
faulty injectors.
* Test coolant temperature sensor and wiring. Repair or replace
as required.
* Inspect intake air components for leaking hoses, connections or
cracks. Repair as required.
* Ensure airflow sensor plate movement and rest position. Adjust
as necessary.
* Test idle switch and idle air stabilizer valve.
* Perform system electrical checks.
* Check airflow meter. Replace if faulty.
* Ensure idle RPM is correct.
* Check auxiliary air by-pass regulator.
* Check fuel injector electrical connections.
* Use stethoscope to verify fuel injectors are operating.
* Ensure sufficient secondary spark is available in all cylinders.
* Verify vacuum hose routing is correct and there are no
vacuum leaks.
* Check idle stabilizer operation.
* Check for EGR system malfunction (if equipped).
* Check O2 sensor operation.
* Check for distortion or cracks in fuel injector(s) plastic
connecting flange(s).
* Check for use of poor quality fuel containing insufficient

H - TESTS W/O CODES
Article Text (p. 4)
1990 Volkswagen Corrado
For Volkswagen Technical Site: http://vw.belcom.ru
Copyright © 1998 Mitchell Repair Information Company, LLC
Thursday, March 23, 2000 09:45PM
cleaning additives. Prolonged use of poor quality fuel can
cause injector clogging and carbon build-up on intake system.
ENGINE MISFIRES OR HESITATES
CIS-E & CIS-E MOTRONIC
* Ensure injector spray patterns and volume are correct. Replace
faulty injectors.
* Check fuel system and control system pressure. Replace pressure
regulator if necessary.
* Check Oxygen (O2) sensor system operation.
* Check fuel lines and connections for leaks.
* Test coolant temperature sensor and wiring. Repair or replace
as required.
* Check airflow meter and throttle switch. Replace if faulty.
* Ensure vacuum hoses are not disconnected or damaged.
* Ensure electrical harness connectors and wires are not
broken or loose.
* Check cold start valve for leaking (engine warm).
DIGIFANT II
* Check airflow sensor flap and sensor resistance. Replace
if faulty.
* Inspect intake air components for leaking hoses, connections
or cracks. Repair as required.
* Test intake air preheating system. Replace faulty components
as required.
* Check fuel system and control system pressure. Replace pressure
regulator if necessary.
* Ensure vacuum hoses are not disconnected or damaged.
* Ensure electrical harness connectors and wires are not
broken or loose.
* Check cold start valve for leaking (engine warm).
* Check coolant temperature sensor operation.
* Check Oxygen (O2) sensor voltage output.
EXCESSIVE FAST IDLE
* Inspect accelerator pedal and cable for worn parts or binding.
* Test idle switch (if equipped).
* Test auxiliary air regulator and replace if necessary
(if equipped).
* Inspect throttle valve and adjust or replace as required.
* Check carbon canister solenoid valves (CIS-E Motronic).
* Test idle boost valve system operation (1.8L 8-valve engine
only). Replace faulty parts as necessary.
* Test coolant temperature sensor and wiring (Digifant II). Repair
or replace as required.
* Check throttle cable adjustment.
* Verify vacuum hose routing is correct.

H - TESTS W/O CODES
Article Text (p. 5)
1990 Volkswagen Corrado
For Volkswagen Technical Site: http://vw.belcom.ru
Copyright © 1998 Mitchell Repair Information Company, LLC
Thursday, March 23, 2000 09:45PM
* Ensure there are no vacuum leaks.
* Check idle stabilizer operation (if equipped).
* Ensure fuel system pressure and volume are correct.
* Check auxiliary air by-pass regulator.
* Check cold start valve for leaking (engine warm).
ENGINE HESITATES ON ACCELERATION
* Inspect intake air components for leaking hoses
* Check injector spray pattern. Check for faulty injectors.
* Check cold start valve for leaking (engine warm).
* Check airflow sensor plate movement. Replace fuel distributor
as necessary.
* Check airflow sensor plate position. Adjust as necessary.
* Check fuel system and control system pressure. Replace pressure
regulator if necessary.
* Test airflow sensor plate potentiometer. Adjust or replace
as necessary.
* Perform system electrical checks.
* Check idle mixture CO adjustment. Adjust as necessary.
ENGINE LACKS POWER
* Test coolant temperature sensor and wiring. Repair or
replace as required.
* Check fuel system and control system pressure. Replace pressure
regulator if necessary.
* Check throttle cable adjustment.
* Check throttle switch. Adjust or replace as necessary.
* Check airflow sensor screen for damage or incorrect installation
(if equipped).
* Check ignition timing and knock sensor control (if equipped).
Adjust as necessary.
* Check EGR system for correct operation (if equipped).
* Ensure base timing is correct and timing advance system
is functional.
* Check transmission for correct downshift (auto. trans.)
* Check fuel tank filler tube for tampering of restrictor. If
tampering has occurred, check catalytic converter for lead
contamination and exhaust system restriction.
* Check for use of poor quality fuel containing insufficient
cleaning additives. Prolonged use of poor quality fuel can
cause injector clogging and carbon build-up on intake system.
* Inspect intake air element, housing, and preheating system.
* Check airflow sensor plate movement. Replace if necessary.
POOR FUEL MILEAGE
* Ensure idle speed, base timing and timing advance are
set to specifications.
* Check cold start valve for leaking (engine warm).

H - TESTS W/O CODES
Article Text (p. 6)
1990 Volkswagen Corrado
For Volkswagen Technical Site: http://vw.belcom.ru
Copyright © 1998 Mitchell Repair Information Company, LLC
Thursday, March 23, 2000 09:45PM
* Check fuel system and control system pressure. Replace
pressure regulator if necessary.
* Check thermo time switch operation.
* Check airflow sensor voltage output.
* Check air induction system for leaks.
* Check fuel injector operation.
* Check coolant temperature sensor operation.
* Check Oxygen (O2) sensor operation.
ENGINE DIESELING
CIS-E & CIS-E MOTRONIC
* Ensure ignition timing and timing advance are set to
specifications.
* Check for engine overheating.
* Check cold start valve for leaking (engine warm).
* Check for leaking injectors.
* Check airflow sensor plate/control plunger rest position.
Adjust as necessary.
* Check carbon canister solenoid valve.
* Verify no leaks in exhaust system.
FAILED EMISSIONS TEST
* Test lambda control system. Replace if faulty.
* Check air/fuel mixture. Adjust if necessary.
* Ensure air intake system is not restricted.
* Ensure engine is at normal operating temperature.
* Ensure fuel system pressure is correct.
* Check cold start valve for leaking (engine warm).
* Check thermo time switch operation.
* Verify base timing is correct.
* Check for correct PCV valve operation.
* Check crankcase for gasoline contamination.
* Check idle stabilizer operation.
* Check EGR system for correct operation (if equipped).
* Check vapor recovery system operation.
* Check operation of coolant temperature sensor.
* Check fuel tank filler tube for tampering of restrictor.
If tampering has occurred, check catalytic converter for
lead contamination and exhaust system restriction.
* Check for use of poor quality fuel containing insufficient
cleaning additives. Prolonged use of poor quality fuel can
cause injector clogging and carbon build-up on intake system.
INTERMITTENT PROBLEM DIAGNOSIS
Intermittent fault testing requires duplicating circuit or
component failure to identify the problem. If necessary, monitor
voltage or resistance values using a DVOM while attempting to

I - SYSTEM/COMPONENT TESTS
Article Text
1990 Volkswagen Corrado
For Volkswagen Technical Site: http://vw.belcom.ru
Copyright © 1998 Mitchell Repair Information Company, LLC
Thursday, March 23, 2000 09:46PM
ARTICLE BEGINNING
1990 ENGINE PERFORMANCE
Systems & Component Testing
Volkswagen; Cabriolet, Corrado, Fox, Golf GL/GTI,
Jetta, Vanagon
INTRODUCTION
Before testing separate components or systems, perform
procedures in F - BASIC TESTING and H - TESTS W/O CODES articles.
NOTE: Testing individual components does not isolate shorts or
opens. Perform all voltage tests with a Digital
Volt-Ohmmeter (DVOM) with a minimum 10-megohm input
impedance, unless stated otherwise in test procedure. Use
ohmmeter to isolate wiring harness shorts or opens.
AIR INDUCTION SYSTEMS (SUPERCHARGER)
BOOST PRESSURE
1) Before checking supercharger boost pressure, ensure engine
idle speed is correct. See D - ADJUSTMENTS article. Ensure engine oil
temperature is 176øF (80øC). Check knock sensor operation. See KNOCK
SENSOR under IDLE CONTROL SYSTEM in this article.
2) Connect Pressure Gauge (VW1397) or equivalent to the
pressure regulator hose using adapter "T". Open pressure gauge check
valve to position "A" and start engine.
3) Remove harness connector from CO potentiometer and Blue
connector from temperature sensor (in front flange on cylinder head).
Accelerate to full throttle. Engine speed must increase periodically
then drop (surge). Watch pressure gauge, boost pressure must reach 8.7
psi (0.6 kg/cm
ý). If boost does not reach specification, check for
leaks in air system and correct by-pass valve setting. Check
supercharger.
COMPUTERIZED ENGINE CONTROLS
NOTE: For fuel system used on model being tested, see FUEL SYSTEM
APPLICATION table.
FUEL SYSTEM APPLICATION
ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄApplication Fuel System
Cabriolet, Corrado, Golf GL/GTI,
Jetta & Vanagon .................................. AFC-Digifant II
Fox .......................................................... CIS-E
Jetta GLi ............................................. CIS-Motronic

I - SYSTEM/COMPONENT TESTS
Article Text (p. 3)
1990 Volkswagen Corrado
For Volkswagen Technical Site: http://vw.belcom.ru
Copyright © 1998 Mitchell Repair Information Company, LLC
Thursday, March 23, 2000 09:46PM
circuits to ECU. The ECU engine ground is near ignition distributor.
Remove ECU connector. Check resistance to ground on terminal No. 35.
Resistance should be zero ohms. If resistance is not zero ohms, repair
open or short in wiring.
POWER CIRCUITS
Turn ignition off. Disconnect ECU connector. Using a
voltmeter, check terminals No. 12, 14, 19 and 34 for battery voltage.
If battery voltage is not present. Check fuses No. 15, 18 and 24. If
fuses are okay, check for open in wiring between ECU and fuse box. See
L - WIRING DIAGRAMS for terminal identification and wire colors.
ENGINE SENSORS & SWITCHES
AIRFLOW SENSOR (FOX & JETTA GLI)
1) Start engine to pressurized fuel system. Turn engine off
and remove intake boot from top of airflow sensor. Disconnect coil
secondary wire from coil and jumper to ground.
2) Check sensor play by slowly moving sensor plate through
travel range with a magnet. See Fig. 1. Resistance should be felt.
Move plate back to the rest position. There should be no resistance.
If binding is felt, loosen sensor plate hold-down bolt and adjust
plate to center of venturi.
3) If resistance is uneven, remove airflow sensor from
housing to clean and lubricate lever assembly. If resistance is caused
by control plunger, remove and clean control plunger assembly. If
binding continues, replace fuel distributor.
4) Check position of airflow sensor plate. Airflow sensor
plate edge must be within .075" (1.9 mm) below the narrowest section
of the venturi. If not, bend sensor spring until correct specification
is obtained. Ensure a small gap exists between sensor lever and
control plunger.Fig. 1: Identifying Airflow Sensor Components (Fox & Jetta GLi)
Courtesy of Volkswagen United States, Inc.
AIRFLOW SENSOR (GOLF & JETTA)
1) Start engine to pressurized fuel system. Turn engine off

I - SYSTEM/COMPONENT TESTS
Article Text (p. 4)
1990 Volkswagen Corrado
For Volkswagen Technical Site: http://vw.belcom.ru
Copyright © 1998 Mitchell Repair Information Company, LLC
Thursday, March 23, 2000 09:46PM
and remove intake boot from top of airflow sensor. Check sensor plate
by lifting plate through travel cycle with magnet or pliers.
2) Continuous resistance should be felt. Move plate back to
rest position. There should be no resistance. If resistance is felt,
replace airflow sensor. If sensor plate lever is difficult to move
upward but moves freely downward, check sensor plate for correct
centering.
3) Sensor plate should be evenly centered in the housing with
plate edge at the narrowest section of the venturi while at rest
position. If sensor plate adjustment is correct, check control plunger
for sticking. If control plunger is sticking, replace fuel distributor
assembly.
AIRFLOW SENSOR (VANAGON)
1) Turn ignition off. Remove Electronic Control Unit (ECU)
connector. Attach ohmmeter to ECU connector. See Fig. 3. Resistance
should correspond to ECU PIN CHECK in AFC-DIGIFANT II AIRFLOW SENSOR
RESISTANCE table.
2) With ignition off, unplug connector from airflow sensor.
Attach ohmmeter to airflow sensor terminal. See Fig. 2. Resistance
should correspond to AIRFLOW SENSOR PIN CHECK in AFC-DIGIFANT II
AIRFLOW SENSOR RESISTANCE table.
AFC-DIGIFANT II AIRFLOW SENSOR RESISTANCEÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄTerminal Ohms
ECU Pin Check
No. 6 & No. 17 .......................................... 500-1000
No. 17 & No. 21 .............................................. (1)
Airflow Sensor Pin Check
No. 3 & No. 4 ........................................... 500-1000
No. 2 & No. 3 ................................................ (1)
(1) - Resistance should fluctuate as sensor door is moved.
ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄFig. 2: Identifying AFC-Digifant II Airflow Sensor & Terminals
Courtesy of Volkswagen United States, Inc.