System/component Tests Audi 90 B3

INTRODUCTION

Prior to testing separate components or systems, it is highly recommended that all procedures listed in BASIC TESTING article be performed. Since many computer controlled and monitored components will set a trouble code if they malfunction, it is also recommended that self-diagnosis be performed. See TESTS W/CODES article.

Note. Testing of individual components does not isolate possible shorts or opens in the control harness of electronically controlled systems. Use an ohmmeter to isolate shorts or opens in harness. All voltage tests should be performed with a Digital Volt Ohmmeter (DVOM) with a minimum 10-megohm input impedance, unless specifically stated different in testing procedures.

TURBOCHARGER

Note. Check the following items. If found defective, replace turbocharger assembly. If related parts are defective, repair or replace.

Vibration Or Noise

1. Inspect for defective bearings or interference of rotating parts with related objects. Consider neglect of engine oil change, sustained use with contamination in oil pipe, a restricted or broken oil filter. Check for repeated abrupt starts and stops that could cause bearing failure.
2. If no problem exists with lubricating system, an incorrectly balanced rotating section or bent shaft may be suspected. This is due to excessive wear of bearings or contamination that has caused damage to turbine or compressor wheels.
3. If any of the above mentioned conditions exist, turbocharger assembly must be replaced. Before a new turbocharger assembly is installed, carefully check intake manifold system for contamination and/or broken turbine or compressor wheel pieces.

Low Boost Pressure

1. Check air cleaner element for contamination or clogging and clean or replace element as necessary. If turbine or compressor wheels do not rotate smoothly and lightly when turned by hand, replace turbocharger assembly. Inspect for wastegate valve or relief valve which may be left open.
2. If turbocharger appears to be in good condition, but has low boost pressure, check for the following: Gas leaks in exhaust system. Deformed or clogged exhaust pipe or muffler which may cause increased exhaust resistance. Air leaks from compressor discharge side.

White Exhaust Smoke

Sustained engine operation with faulty bearings will result in failure of oil seal which can permit engine oil leakage into exhaust and intake pipes. Leakage of engine oil from turbocharger into exhaust pipe or intake pipe will result in White colored exhaust. If this occurs, inspect for clogged, crushed or deformed oil return pipe. Leakage may also be die to worn piston ring (seal ring) in turbocharger.

Boost Pressure

1. To test turbocharging system, use Pressure Gauge (VW 1397). Gauge is equipped with a valve which locks pressure measurement when closed. CAUTION: This operation requires the use of a chassis dynamometer to safely test components. If dynamometer is not available, testing can be simulated with a road test and the correct equipment arrangement.
2. Attach gauge to vacuum advance at distributor, using "T" fitting supplied with gauge. Ensure vacuum advance unit and charcoal canister purge valve are free of leaks. Use hose clamps at all connections to avoid low readings.
3. Warm engine until oil temperature is above 176°F (80°C). Accelerate engine to 4000 RPM in second gear with automatic transmission (third gear on manual transmission). Hold vehicle speed constant and close gauge shut-off valve. Record reading. NOTE: Testing should not exceed 10 seconds at full boost.
4. Boost pressure readings will vary with temperature. Compare results with readings in «BOOST PRESSURE SPECIFICATIONS»(/audi/90/b3-1987-1991/remont/testing-diagnostics/#systemcomponent-tests) table.
5. If boost pressure is incorrect, replace wastegate as a testing measure and retest. If boost pressure is still incorrect, replace turbocharger.

BOOST PRESSURE SPECIFICATIONS

Scheme 20

1. Attach dial indicator to the turbocharger. (Scheme 20) Zero dial indicator, with 1 mm preload, pointing toward turbocharger shaft. Move shaft backward and forward. Maximum end play should be.008" (.2 mm).
2. Mount dial indicator with stem on side of turbocharger shaft end nut. Zero dial indicator, with.040" (1.0 mm) preload, pointing toward hub of shaft. Push shaft toward dial indicator and return. Maximum side play should be.022" (.55 mm).

Wastegate Solenoid

1. Remove connector from multi-thermo switch and turn ignition on. Energize wastegate solenoid by momentarily brushing lead to wastegate solenoid at multi-thermo switch. Solenoid will click if operating properly.
2. Remove connector from wastegate solenoid. Check voltage at connector terminal No. 1 (Green/Purple wire). Voltage should read approximately 12 volts. Turn ignition off and remove connector from electronic control unit.
3. Using an ohmmeter, measure resistance between terminal No. 2 (Blue/Black wire) and terminal No. 19. Ohmmeter should read zero ohms. If not, check for open circuit in wiring or connectors. If circuits are functional, replace wastegate solenoid.

CIS Digital Control (ECU Voltage Supply)

1. Unplug ECU harness connector. Connect voltmeter positive test lead to pin No. 35. (Scheme 21) With ignition switch on, voltmeter should indicate 12 volts with negative test lead touching either No. 18 and No. 9. If not, repair ignition circuit 15 or battery to ignition switch.
2. Turn ignition switch off. Connect positive voltmeter lead to terminal No. 32 and negative lead to No. 9. With ignition switch on, ensure 12 volts are present when brake pedal is depressed. If not, check wiring for open or check brake light switch. Turn ignition switch off. Reconnect ECU harness connector.

Scheme 21

CIS-E III

Manufacturer's information is not available.

CIS Motronic

Manufacturer's information is not available.

Air Temperature Sensor

1. Turn ignition off. Disconnect ECU harness connector. Check for about 400-700 ohms in circuit between ECU terminals No. 23 and 24. (Scheme 21) If ohms are not as specified, peel back air temperature connector boot.
2. Ensure air temperature sensor resistance is 400-700 ohms. If not, replace sensor. If required, cut sensor terminals from harness and solder new sensor to harness. If sensor is okay, check for an open or shorted circuit in wires.

Coolant Temperature Sensor

1. Disconnect wire from coolant temperature sensor. Ensure coolant temperature sensor resistance is 60-1000 ohms. If not, replace sensor. If okay, disconnect ECU harness connector.
2. Check for continuity in wire between ECU terminal No. 10 and coolant temperature sensor. (Scheme 21) If no continuity, check for an open circuit in wire.

Engine Speed Sensors

1. Remove Gray (engine RPM) and Black (ignition timing reference) connectors from bracket near ignition coil. Connect ohmmeter to each sensor connector terminals No. 1 and 2. (Scheme 22) Ohmmeter reading should be 1000 ohms.
2. If not, replace sensor(s). If reading is correct, check continuity between each sensor connector terminals No. 1 and 3, and 2 and 3. If ohmmeter reading is not infinity (4), replace sensor(s).
3. Unplug connector from ECU. Check wiring between harness side of each sensor connector and ECU. (Scheme 21)and (Scheme 22). Ensure each wire between ECU and sensor connectors has zero ohms of resistance. See ENGINE SPEED SENSOR CIRCUITS chart.

Scheme 22

Knock Sensor

If engine knocking is present, knock sensor will produce a small voltage of about 50-70 millivolts. If engine knocking continues, check fuel quality, compression pressure, knock sensor and wiring circuits. No other tests are available from the manufacturer.

A/C Compressor Clutch (On/Off Signal)

1. With ignition off, disconnect Fuel Injection Control Unit (FICU) harness connector. Connect multimeter between terminals No. 33 and No. 35 (ground). (Scheme 23) With A/C on "OFF" position, turn ignition on.
2. Multimeter should read zero volt. If reading is not as specified, repair break in wiring. With A/C in "AUTO" or "BI-LEVEL" position, turn ignition on.
3. A/C compressor clutch must cycle on and have 12 volts present at compressor clutch connector. If compressor does not cycle on or have 12 volts present at connector, repair break in wiring.

Scheme 23

Altitude Sensor (Voltage Supply)

1. With ignition off, remove altitude sensor harness connector. Connect multimeter between harness connector terminal No. 1 and engine ground. (Scheme 24)
2. Turn ignition on. Multimeter should read 5 volts. If 5 volts is not present, repair break in wiring between terminal No. 1 of altitude sensor connector and terminal No. 25 of FICU harness control.
3. With ignition off, connect multimeter between terminals No. 1 and No. 3 of altitude sensor. Connect multimeter between terminals No. 2 and No. 3. Turn ignition on. Multimeter should read 4.5-5.0 volts.
4. If no voltage is present, repair break in wiring or replace FICU. Check wiring between ICU and altitude sensor. If voltage is present and all wiring is good, replace altitude sensor.

Scheme 24

1. Ensure engine temperature is greater than 176°F (20°C). Remove harness connector from coolant temperature sensor. Connect multimeter between temperature sensor terminal No. 1 and engine ground.
2. Connect between terminal No. 2 and engine ground. For multimeter reading, see COOLANT TEMPERATURE SENSOR chart. Connect multimeter between harness connector terminal No. 1 and ground, then between terminal No. 2 and ground.
3. Turn ignition on. Multimeter should read 4.5-5.5 volts. If no voltage is present, repair break in wiring. If no voltage is present and no break in wiring is found, replace respective control unit that controls that temperature sensor.

Scheme 25

1. Connect multimeter between terminal No. 3 of throttle switch and ground. Turn ignition on. Multimeter should read battery voltage. Fasten pointer for Protractor (3084) to adjuster for accelerator cable (using a rubber band). (Scheme 25)
2. Screw protractor onto throttle shaft and unscrew throttle shaft nut (if necessary). Push throttle lever to full open (at stop limit) and zero pointer plus disc.
3. Close throttle to 30 degrees, then slowly move toward full throttle position until full throttle switch engages (zero ohms indicated). Protractor should show 6-14 degrees before contacting full throttle limit stop.
4. If degrees are not as specified, replace and adjust full throttle switch. If degrees are as specified, check wiring between throttle switch harness connector and FICU by removing FICU harness connector.
5. Turn ignition off. Using multimeter, check continuity between throttle switch connector terminal No. 1 and ICU connector terminal No. 7. (Scheme 24) Then check continuity between throttle switch connector terminal No. 3 and ICU connector terminal No. 9. Multimeter should read.2 ohm.
6. Connect multimeter and check continuity between throttle switch connector terminal No. 1 and FICU connector terminal No. 28. Then check continuity between throttle switch connector terminal No. 3 and FICU connector terminal No. 31. Multimeter should read.2 ohm. If.2 ohm is not present, repair break in wiring.

Idle & Full Throttle Switch

1. With ignition off, remove harness connector to idle and full throttle switch on throttle body. Connect Test Adapter (VW 1501) between throttle switch and harness connector. (Scheme 26)
2. Connect multimeter between terminal No. 2 of adapter and engine ground. Turn ignition on. Multimeter should read 12 volts. If 12 volts is not present, repair break in wiring.

Scheme 26

Idle Switch

1. Connect multimeter between terminal No. 1 of Test Adapter (VW 1501) and ground. Multimeter should read battery voltage. Turn ignition off. Switch multimeter to ohms range.
2. Move throttle valve.20-.28" (.5-.7 mm). Measurement is made with feeler gauge between throttle valve stop and adjustment screw. Resistance should change from zero ohm (with throttle closed) to infinity as throttle gap increases beyond.020" (.5 mm).
3. If resistance is not as specified, adjust idle gap to.006-.020" (.15-.5 mm). (Scheme 27) If resistance is as specified, check full throttle switch.

Scheme 27

Oxygen Sensor

1. Disconnect differential pressure regulator connector from side of regulator. Using Adapter (1315 A/1), connect Multimeter (US 1119) to differential pressure regulator and to the connector removed from regulator.
2. Set multimeter to 200 mA DC scale. Disconnect O2 sensor connector. Start engine and let idle. Note reading on multimeter. Ground male end of O2 sensor connector.
3. Observe multimeter. Current should increase from 9 mA to 11 mA after 15 seconds. If multimeter reading is not as specified, check wiring between FICU and O2 sensor harness connector.
4. If no break in wiring is found, replace FICU. Reconnect O2 sensor (Green) wire. Start engine. Raise engine speed to approximately 3000 RPM for a few seconds.
5. Differential pressure regulator current must return to original mA value and fluctuate approximately 1-3 mA in -10 mA to +10 mA range. If current does not return to original mA value or does not fluctuate, replace O2 sensor.

Scheme 28

Scheme 29

1. Ensure engine is at normal operating temperature. Connect Test Adapter (VW1501) between potentiometer and harness. (Scheme 28) Connect multimeter to test adapter connectors 1 and 3. Switch multimeter to DC volts scale and turn on ignition. Reading should be 4.35-5.35 volts.
2. Switch multimeter leads to test connectors 2 and 3. Start engine and let idle. Engine cooling fan must not come on during this test. Reading should be.4-.9 volt. If reading is slightly outside tolerance, correct by adjusting the potentiometer trim screw. If correction is not possible, replace potentiometer.
3. When replacing potentiometer, do not touch resistance strip or contact whiskers inside potentiometer. Loosely install potentiometer. Connect multimeter to test adapter connectors 2 and 3. Turn on ignition and measure voltage. Reading should be 10-100 mV. Adjust potentiometer to read correctly by turning trim screw.
4. Pull adjusting slide on Sensor Plate Gauge (VW1348/1) up to upper stop. Place gauge centrally on edge of airflow sensor with edge No. 3 pointing toward fuel distributor. (Scheme 29) Push adjusting slide down to stop. Rotate setting screw until base of magnet contacts sensor plate mounting screw.
5. Pull adjusting slide up to first stop (idle position). Adjust potentiometer set screw to obtain.5-.8 volt.
6. Remove sensor plate gauge and install intake air boot. Start and run engine until cooling fan has cycled at least once. DO NOT take voltage readings while engine is running.
7. Stop engine and turn on ignition. Potentiometer voltage should be.4-.9 volt. If voltage reading is out of range, refer to step 2) for procedure. If you have performed all of these procedures and still cannot obtain correct voltage readings, replace airflow sensor.

1. Ensure engine temperature is greater than 176°F (80°C). Remove harness connector from coolant temperature sensor. Connect multimeter between temperature sensor terminal No. 1 and engine ground.
2. Turn ignition on. Multimeter should read 4.5-5.5 volts. If no voltage is present, repair break in wiring. If no voltage is present and no break in wiring is found, replace respective control unit that controls that temperature sensor.

Full Throttle Switch

1. Connect multimeter between terminal No. 3 of throttle switch and ground. Switch multimeter to voltage range. Turn ignition on. Multimeter should read battery voltage. Fasten pointer for Protractor (3084) to adjuster for accelerator cable (using a rubber band).
2. Screw protractor onto throttle shaft and unscrew throttle shaft nut (if necessary). Push throttle lever to full open (at stop limit) and zero pointer plus disc.

Scheme 30

1. With ignition off, remove harness connector to idle and full throttle switch on throttle body. Connect Test Adapter (VW 1501) between throttle switch and harness connector. (Scheme 30)
2. Connect multimeter between terminal No. 2 of adapter and engine ground. Turn ignition on. Multimeter should read 12 volts. If 12 volts is not present, repair break in wiring.

1. Connect multimeter between terminal No. 1 of Test Adapter (VW 1501) and ground. Multimeter should read battery voltage. Turn ignition off. Switch multimeter to ohms range.
2. Move throttle valve .20-.28" (.5-.7 mm). Measurement is made with feeler gauge between throttle valve stop and adjustment screw. Resistance should change from zero ohm (with throttle closed) to infinity as throttle gap increases beyond .020" (.5 mm).
3. If resistance is not as specified, adjust idle gap to .006-.020" (.15-.5 mm). If resistance is as specified, check full throttle switch.

1. Ensure engine is at operating temperature. Idle speed adjustment, voltage to O2 sensor heater and coolant temperature sensor must all be correct.
2. Connect multimeter to differential pressure regulator using Adapter (1315A/1). (Scheme 31) Start engine and idle for 2 minutes. Note control voltage at differential pressure regulator.
3. Remove a manifold vacuum hose to induce a lean mixture. Control voltage must increase. If control voltage did not change, disconnect O2 sensor wire connector and ground harness end for 20 seconds. If control voltage changes, replace O2 sensor.
4. If control voltage still does not change, perform wire harness checks for opens or shorts to ground or power. If harness checks okay, replace ECU.

Scheme 31

Fuel Pump Relay

1. Remove fuel pump relay from relay board. Turn ignition on. Test light should light when connected between socket for relay terminal No. 46 and ground. (Scheme 32)
2. While starter motor is operating, test light should flicker when connected between sockets for relay terminals No. 50 and 51. Test light should light when connected between sockets for relay terminals No. 46 and 50. Test light should light when connected between sockets for relay terminals No. 46 and 52.
3. If test light does not light up for all tests, check wiring for continuity. If test light does light up for all tests but there is no voltage at fuel pump with relay installed, replace fuel pump relay.

Scheme 32

Oxygen Sensor Heating Element

1. With engine cold, disconnect oxygen sensor heater connection. Connect ohmmeter between male terminals of sensor connector. Start and idle engine. Resistance should be 2-4 ohms. If resistance is incorrect replace oxygen sensor.
2. Connect voltmeter between terminals of oxygen sensor female connector. Battery voltage should be present. If not, check continuity of wiring back to fuel pump relay.

Fuel Pump Relay Control

1. With ignition off. Remove fuel pump relay from relay panel. Connect multimeter between terminals No. 48 and No. 50 of relay socket. (Scheme 33)
2. Multimeter should read 12 volts. Connect multimeter between terminals No. 46 and No. 50 of relay socket. Turn ignition on. Multimeter should read 12 volts.
3. If multimeter does not read as specified, repair break in wiring. Connect multimeter between terminals No. 46 and No. 47 of relay socket. Momentarily engage starter. Multimeter should read 7 volts.
4. If multimeter does not read 7 volts, partially remove ICU and disconnect harness connector. Using a multimeter, check continuity between ICU and relay socket.
5. Connect terminal No. 3 of ICU connector to terminal No. 49 of relay socket. Connect terminal No. 14 of ICU and terminal No. 47 of relay socket. Multimeter should read.2 ohm.
6. If reading is not as specified, repair break in wiring. If reading is as specified, replace knock sensor.

Scheme 33

O2 Sensor Heating Element

1. To check O2 sensor heating element, disconnect O2 sensor heating element connector from harness connector. Connect multimeter between connector terminal No. 1 and No. 2. (Scheme 34)
2. Turn ignition on. Multimeter should read 12 volts. If multimeter does not read as specified, repair break in wiring. Connect multimeter between terminals No. 1 and No. 2 of O2 sensor heating element connector. (Scheme 35)
3. Multimeter should read 3-15 ohms. If multimeter does not read as specified, replace O2 sensor.

Scheme 34

Scheme 35

FUEL DELIVERY

See BASIC TESTING .

Cold Start Valve

1. Check cold start valve with engine coolant temperature below 86°F (30°C). Disconnect and ground high tension lead at distributor cap end. Remove cold start valve from intake manifold with wiring and fuel line connected. Point tip into safe container.
2. Crank starter for 10 seconds. Valve should emit cone-shaped spray for time allowed by ECU. If no fuel sprays and fuel pressure is present, test system control in «TESTS W/CODES»(/audi/90/b3-1987-1991/remont/testing-diagnostics/#tests-wcodes) article in this section. Dry off tip and check for leaks. Acceptable leakage rate of cold start valve is one drip per minute or less.

Cold Crank Enrichment

1. Connect Dwell Meter (VW 1367) to vehicle. Using Adapter Cable (US 1112) connect Green test lead to OXS system test connector (Blue/Black wire). Set "%" button on duty meter.
2. Ensure engine is below 68°F (20°C). Unplug and ground high tension spark lead at coil. Crank engine and check that duty cycle is a constant 80%. If not, check coolant sensor. If sensor is okay replace ECU.
3. If duty cycle reading is okay, but cold start problems are present, check cold start valve and idle stabilization system.

Cold Engine Warm-Up Enrichment

1. Connect Dwell Meter (VW 1367) to vehicle. Using Adapter Cable (US 1112) connect Green test lead to OXS system test connector, located near fuel filter, (Blue/Black wire). Set "%" button on duty meter.
2. Ensure engine is below 68°F (20°C). Start engine. Duty cycle should be at least 80%. After 30-60 seconds, duty cycle should gradually drop. If not, check coolant sensor and wiring circuits to coolant sensor. If okay replace ECU.

Deceleration Fuel Shut-Off Check (Man. Trans. Only)

1. Engine oil temperature must be at minimum of 120°F (50°C). Reconnect wiring to temperature sensor. Start engine and run it at 2000 RPM briefly. Release throttle.
2. If intake boot does not visibly contract, disconnect harness plug from deceleration fuel shut-off valve. Attach a voltmeter to harness terminals. Start engine and run it at 2000 RPM briefly. Release throttle.
3. If 12 volts are present, ensure vacuum hose is okay and replace deceleration fuel shut-off valve. If 12 volts were not present, check operation and adjustment of throttle switch at idle. If okay, check throttle switch to ECU wiring for open.
4. If deceleration fuel shut-off valve still does not operate, connect Dwell Meter (VW 1367) to vehicle. Using Adapter Cable (US 1112) connect Green test lead to OXS system test connector. Set "%" button on duty meter. Disconnect harness connector from deceleration fuel shut-off valve. Using a jumper wire, connect terminal No. 2 to ground.
5. If duty meter does not indicate 40%, turn ignition off. Disconnect ECU harness connector. Check for 0.2 ohms in wire between ECU terminal No. 4 and deceleration fuel shut-off valve terminal No. 2. (Scheme 21) If ohms are not as specified, check for an open circuit in wire. If circuit is not open, replace ECU.

Full Throttle Enrichment

1. Connect Dwell Meter (VW 1367) to vehicle. Using Adapter Cable (US 1112) connect Green test lead to OXS system test connector (Blue/Black wire). Set "%" button on duty meter.
2. Disconnect vacuum hose going to ECU. Remove throttle switch. Start and allow engine to idle. Bridge throttle switch terminals No. 2 and 3. Ensure that duty meter indicates a constant 60% duty cycle. If not, check continuity of throttle switch wiring back to ECU.

OXS Frequency Valve

1. Disconnect harness connector from OXS frequency valve. Using a LED Test Light (US 1115), connect Red lead to terminal No. one and Black lead to terminal No. 2.
2. Perform output code self-diagnosis as previously described. When code appears, LED test light must be off. If light is off, replace OXS frequency valve.
3. If light came on, ensure 12 volts are present between oxygen sensor terminal No. 1 and ground. If necessary, repair wiring or circuits.
4. If 12 volts are present, turn ignition off. Disconnect ECU harness connector. Check for about 10 ohms in wire between ECU terminal No. 8 and oxygen sensor terminal No. 2. (Scheme 21) If ohms are not as specified, check for an open circuit in wire. If circuit is not open, replace ECU.

System Pressure

1. Remove fuel line from cold start valve. (Scheme 36) Remove test plug from distributor lower chamber. Connect Pressure Gauge (VW 1318) between fuel line from cold start valve and lower chamber. (Scheme 36)
2. Disconnect differential pressure regulator connector from side of regulator. Remove fuel pump relay. Jumper fuel pump relay socket. Open valve on pressure gauge.
3. Energize fuel pump. Note pressure reading on pressure gauge. Pressure should be 88-94 psi (6.2-6.6 kg/cm 2 ). System pressure is not adjustable.

Differential Pressure Regulator Fuel Pressure

Close pressure gauge valve on Pressure Gauge (VW 1318). Disconnect differential pressure regulator connector from side of regulator. Fuel pressure should be 4.5-7.3 psi (.3-.5 kg/cm 2 ) less than noted in SYSTEM PRESSURE test. If not, replace differential pressure regulator.

Differential Pressure Regulator Electrical System

1. Connect Pressure Gauge (VW 1318) as previously described. (Scheme 36) Close pressure gauge valve. Disconnect differential pressure regulator connector from side of regulator.
2. Using Adapter (1315 A/1), connect Multimeter (US 1119) to differential pressure regulator and to connector removed from regulator. (Scheme 37)
3. Set multimeter to 200 mA DC scale. Turn ignition on. Multimeter should read 100 mA. Pressure gauge should read 17-22 psi (1.2-1.5 kg/cm 2 ) less than readings noted in FUEL INJECTION SYSTEM PRESSURE test. If differential pressure is not as specified, check differential pressure regulator wiring and connectors. If wiring and connectors are good, replace differential pressure regulator.

Scheme 36

Residual Pressure

1. Connect Pressure Gauge (VW 1318) as previously described. (Scheme 37) Open pressure gauge valve. Operate fuel pump for at least 30 seconds.
2. Shut off fuel pump. Note system pressure. Pressure should be 51 psi (3.6 kg/cm 2 ) after 10 minutes and 49 psi (3.4 kg/cm 2 ) after 20 minutes.

Note. Residual Pressure Test does not include cold start valve. To check cold start valve, reattach fuel line. Operate fuel pump. Visually check for leaks.

Cold Acceleration Enrichment

1. Disconnect differential pressure regulator connector from side of regulator. Using Adapter (1315 A/1), connect Multimeter (US 1119) to differential pressure regulator and to connector removed from regulator. NOTE: Coolant temperature must be below 104°F (40°C) to perform Cold Acceleration Test.
2. Set multimeter to 200 mA DC scale. Disconnect oxygen sensor connector. Start engine and let idle. Note multimeter reading. Accelerate engine. Multimeter reading should increase approximately 6 mA during acceleration.

Deceleration Fuel Shutoff

1. Warm engine to normal operating temperature. Disconnect differential pressure regulator connector from side of regulator.
2. Using Adapter (1315 A/1), connect Multimeter (US 1119) to differential pressure regulator and to connector removed from regulator. Set multimeter to 200 mA DC scale.
3. Accelerate engine to more than 3000 RPM. Release throttle, noting multimeter reading. Reading should decrease to approximately -50 mA with throttle closed until engine speed reaches about 1200 RPM.

Scheme 37

1. Ensure engine is at normal operating temperature. Connect Fuel Pressure Tester (VW1318) to measuring location No. 1 on fuel distributor using Adapter (VW1318/4). Close fuel pressure valve. (Scheme 38)
2. Remove fuel pump relay from fuse panel and connect Remote Control (US4480/3) in fuse panel fuel pump relay cavity. Ensure fuse No. 13 on fuse panel is good.
3. Open valve on pressure tester and energize fuel pump with remote control. Fuel pressure should be 89-94 psi. (6.3-6.6 kg/cm 2 ). If fuel pressure is too high, carefully remove fuel return line from fuel pressure regulator and place in container.
4. Repeat test in step 2). If fuel pressure is still too high, replace fuel pressure regulator. If pressure is okay, check return line for obstruction or kinks. Repair or replace as necessary.

1. Ensure engine is at normal operating temperature and no fault codes are stored in ECU memory. Using a digital multimeter and Harness Adapter (VW1315A/1), check voltage at differential pressure regulator.
2. Connect multimeter to differential pressure regulator. (Scheme 31) Turn ignition on. Control voltage must read positive (+). If voltage reads negative (-), reverse test leads.
3. Start engine. Raise RPM to 3000 and release throttle. Control voltage must momentarily switch to negative (-). If system fails test, perform electrical tests. See CIS-MOTRONIC VOLTAGE & RESISTANCE TESTS chart. (Scheme 39) If system electrical tests are okay, replace ECU. Clear fault codes.

CIS-MOTRONIC VOLTAGE & RESISTANCE TESTS

Scheme 38

Scheme 39

1. Disconnect and ground ignition coil wire. Disconnect CTS harness connector and insert 15,000 ohm side of Bridge Adapter (VW1490) into CTS harness connector. (Scheme 40)
2. Remove cold start valve and place in container to catch fuel spray. Crank engine. Cold start valve must spray fuel in a uniform cone pattern for 7 seconds.
3. Dry off tip of cold start valve. Inspect valve after one minute to ensure valve is dry and not leaking. Disconnect cold start valve connector and measure resistance across terminals of valve. Resistance should be about 10 ohms.
4. If resistance reading is wrong, replace cold start valve. If resistance value is okay, use multimeter connected to cold start valve harness connector and crank engine. Multimeter should show voltage for 7 seconds. If cold start valve resistance and harness check okay, replace ECU.

Sensor Plate Lever/Control Plunger

1. Remove ignition coil wire and ground. Crank engine for 10 seconds.
2. Using pliers or a magnet, lift sensor plate through entire range. Even resistance should be felt through range of movement. Move sensor plate quickly from raised position to rest position. No resistance should be felt. If resistance is felt, replace airflow sensor.
3. If sensor plate is hard to move in one direction, and easy in opposite direction, control plunger is sticking and fuel distributor must be replaced.

Scheme 40

1. With engine off, upper edge of airflow sensor plate must be.118-.875" (1.9-3.0 mm) below edge of air cone. (Scheme 41)
2. If sensor plate position is incorrect, adjust by bending wire clip located under sensor plate. Try to achieve the smaller setting of.118" (1.9 mm). CAUTION: DO NOT scratch venturi of airflow sensor or bend leaf spring.
3. Airflow sensor plate free play is measured on the fuel distributor side of air plate. see scheme 23 With ignition coil wire disconnected and grounded, crank engine for 10 seconds. Slightly lift airflow sensor plate until resistance is felt. Clearance should be.039-.118" (1.0-3.0 mm).
4. If airflow sensor plate clearance is incorrect, adjust by turning control plunger stop screw. Loosen stop screw lock nut and turn screw. Turning stop screw clockwise increases clearance about.05" (1.3 mm) for each 1/4 turn. Recheck free play and idle speed.

Scheme 41

Differential Pressure Regulator

1. Close valve on fuel pressure tester and relieve pressure. Disconnect harness connector at differential pressure regulator. Energize fuel pump and note fuel pressure. Fuel pressure should be 4.3-7.3 psi. (.3-.5 kg.cm 2 ) below fuel system pressure in step 3) of FUEL SYSTEM PRESSURE test.
2. If fuel pressure difference is not okay, remove small diameter fuel line No. 1 from fuel pressure regulator and place in container. Plug fuel line opening on fuel pressure regulator.
3. Using remote control, energize fuel pump for one minute and measure quantity of fuel in container. Fuel captured in container should be 130-150 ccs. If fuel quantity is less, replace fuel pressure regulator. Reconnect fuel line to fuel pressure regulator.
4. Connect multimeter to differential pressure regulator. (Scheme 31) Disconnect ignition coil wire and ground. Disconnect CTS harness connector and insert 15,000 ohm side of Bridge Adapter (VW1490) into CTS harness connector. (Scheme 40)
5. Crank engine for about 5 seconds and leave ignition on. Using remote control, energize fuel pump and note reading on fuel pressure gauge. Fuel pressure must be 18.9-23.2 psi (1.4-1.6 kg/cm 2 ) below fuel system pressure in step 3) of FUEL SYSTEM PRESSURE test.
6. If fuel pressure difference is not okay, replace differential pressure regulator. If fuel pressure difference is okay, check wiring harness and ECU.

1. This procedure is only required for hot start problems. Turn valve open on fuel pressure tester. Energize fuel pump for 5 seconds using remote control. Note fuel pressure drop over time. Fuel pressure should not drop more than 2 psi in 10 minutes.
2. If fuel pressure drop is greater than 2 psi in 10 minutes, check fuel pump check valve, airflow sensor plate free play and sealing rings on fuel distributor and fuel lines.

Idle Speed Stabilization System

1. Ensure engine temperature is below 68°F (20°C). Disconnect harness connector at the thermoswitch. Check for continuity to ground.
2. If no continuity, replace thermoswitch. If continuity is present, warm thermoswitch to at least 104°F (40°C). Thermoswitch should now show an open circuit. If not, replace thermoswitch.
3. Warm engine to 176°F (80°C) minimum. Disconnect electrical harness for idle stabilizer valve. Connect a voltmeter across both terminals. Turn ignition on. Battery voltage should be present.
4. If battery voltage is present, reconnect idle stabilizer valve. Touch idle stabilizer valve and check for vibrations. If not felt, replace idle stabilizer valve.
5. If no voltage present in step 3), remove idle stabilizer control unit (located in relay panel). Turn ignition on and check for 12 volts between terminals No. 14 (socket 11) and 5 (socket 12).
6. If no voltage present, repair wiring. Turn A/C on, and check for 12 volts between terminal No. 2 (socket 12) and 5 (socket 12). If no voltage, check wiring from A/C relay pin No. 87M.
7. Check resistance between terminals No. 4 (socket 12) and 11 (socket 11). Ohmmeter should indicate 20-40 ohms. If not, check continuity of wiring between idle stabilizer valve and relay board.
8. Ensure throttle switch is at idle position. Check for 12 volts at terminal No. 8 (Gray wire). If voltage is not present, check and adjust throttle switch or repair wiring. With voltage present at idle, slightly open throttle. Ensure voltage drops to zero.
9. Disconnect thermoswitch harness lead. Check for continuity between terminal No. 13 (socket 11) and thermoswitch lead (Blue/Green wire). If no continuity, repair wiring. If all circuits of idle stabilizer system are okay and idle stabilizer valve still does not work, replace idle stabilizer control module.

1. Ensure engine temperature is below 68°F (20°C). Disconnect harness connector at the thermoswitch. Check for continuity to ground.
2. If no continuity, replace thermoswitch. If continuity is present, warm thermoswitch to at least 104°F (40°C). Thermoswitch should now show an open circuit. If not, replace thermoswitch.
3. Warm engine to 176°F (80°C) minimum. Disconnect electrical harness for idle stabilizer valve. Connect a voltmeter across both terminals. Turn ignition on. Battery voltage should be present.
4. If battery voltage is present, reconnect idle stabilizer valve. Touch idle stabilizer valve and check for vibrations. If not felt, replace idle stabilizer valve.
5. If no voltage present in step 3), remove idle stabilizer control unit (located in relay panel). Turn ignition on and check for 12 volts between terminals No. 14 (socket 11) and 5 (socket 12).
6. If no voltage present, repair wiring. Turn A/C on, and check for 12 volts between terminal No. 2 (socket 12) and 5 (socket 12). If no voltage, check wiring from A/C relay pin No. 87M.
7. Check resistance between terminals No. 4 (socket 12) and 11 (socket 11). Ohmmeter should indicate 20-40 ohms. If not, check continuity of wiring between idle stabilizer valve and relay board.
8. Ensure throttle switch is at idle position. Check for 12 volts at terminal No. 8 (Gray wire). If voltage is not present, check and adjust throttle switch or repair wiring. With voltage present at idle, slightly open throttle. Ensure voltage drops to zero.
9. Disconnect thermoswitch harness lead. Check for continuity between terminal No. 13 (socket 11) and thermoswitch lead (Blue/Green wire). If no continuity, repair wiring. If all circuits of idle stabilizer system are okay and idle stabilizer valve still does not work, replace idle stabilizer control module.

Starting Enrichment

1. Ensure engine is at normal operating temperature and no fault codes are stored in ECU memory. Using a digital multimeter and Harness Adapter (VW1315A/1), check voltage at differential pressure regulator.
2. Connect multimeter to differential pressure regulator. (Scheme 31) Remove fuse No. 13 and remove and ground ignition coil wire. Crank engine and observe volt reading. Control voltage should drop to 35-45 mA, during engine cranking, and remain there for a maximum of 3 seconds. After 3 seconds, voltage should drop to zero.
3. With multimeter still connected and ignition off, disconnect O2 sensor and CTS harness connectors. Connect Adjustable Resistance Box (VW1630) leads to CTS harness connectors. Set resistance to 2500 ohms. Install ignition coil wire and start engine. Control voltage should read 15-23mA in about 6-9 seconds, then slowly drop to 9-11 mA.
4. Move throttle quickly to full throttle and release throttle. Control voltage must increase briefly to 6 mA. If system fails test, perform electrical tests. See CIS-MOTRONIC VOLTAGE & RESISTANCE TESTS chart. (Scheme 39) If system electrical tests are okay, replace ECU. Clear fault codes.

Idle Stabilization Valve

1. Close full throttle switch. Idle stabilizer valve should cycle (click sound) when switch is closed. If no click sound is heard, disconnect idle stabilizer valve connector.
2. Connect LED Tester (US 1115) between terminals No. 1 and No. 2 using jumper wire. LED tester should light up. If tester does light up, replace idle stabilizer valve. If tester does not light up, connect multimeter between connector terminal No. 2 and ground.
3. Multimeter should read 12 volts. If 12 volts are not present, repair break in wiring. If wiring is okay, replace ECU.

IGNITION SYSTEM

Note. For basic ignition checks, see BASIC TESTING article.

Hall Effect Sending Unit

1. Remove protective cover from Hall Effect sending unit (on distributor) and unplug connector from unit. Connect voltmeter to connector terminals No. 1 and 3. Turn ignition on. Voltmeter reading should be 9 volts minimum.
2. If reading is incorrect, check for open circuit in wiring between ECU terminals No. 23 and 25, and sending unit. If reading is correct, turn ignition off. Move back connector cover to gain access to rear of 3-wire connector. Reinstall connector to distributor Hall sending unit. Connect voltmeter between terminals No. 1 and 2 at rear of connector.
3. Remove distributor cap, rotor, and dust cover. Turn crankshaft by hand until rotor window clears sending unit. Turn ignition on. Voltmeter should indicate 4 volts minimum.
4. Turn crankshaft until rotor window fully aligns with sending unit. Voltmeter should indicate 0-.5 volts. Turn ignition off. If readings are incorrect, replace Hall sending unit. If readings are correct, check wiring between Hall Effect sending unit and ECU for shorts or opens in wires.
5. Repair wires if necessary. If circuits are okay, replace ECU.

Charcoal Canister Shut-Off Valve

1. Disconnect harness connector from charcoal canister shut-off valve. Using a LED Test Light (US 1115), connect Red lead to terminal No. one and Black lead to terminal No. 2.
2. Perform output code self-diagnosis as previously described. When code 4343 appears, LED test light must be on. If light is on, replace charcoal canister shut-off valve.
3. If light did not come on, ensure 12 volts are present between charcoal canister shut-off valve terminal No. 1 and ground. If necessary, repair wiring or circuits.
4. If 12 volts are present, turn ignition off. Disconnect ECU harness connector. Check for 0.2 ohms in wire between ECU terminal No. 3 and charcoal canister shut-off valve terminal No. 2. If ohms are not as specified, check for an open circuit in wire. If circuit is not open, replace ECU.

See also:
• BASIC TESTING
• TESTS W/CODES
• BOOST PRESSURE SPECIFICATIONS