Bosch Cis Motronic System Audi 80 B3

DESCRIPTION

CIS Motronic system uses a single Electronic Control Unit (ECU). This ECU controls fuel delivery, ignition system and operation of emission control components. The CIS MOTRONIC system also has self diagnostic capabilities.

Input signals from various sensors, switches and signaling devices are constantly monitored for faults. These faults are stored in memory. Fault warning is indicated by flashing from a "FAULT INDICATOR LIGHT" (FIL) located in the instrument cluster.

ELECTRONIC CONTROL UNIT (ECU)

The ECU receives signals from air sensor potentiometer, oxygen sensor, coolant temperature sensor, throttle valve switches and ignition control unit. Using this data, ECU varies air fuel mixture and ignition timing as necessary. The ECU is located behind glove box next to heater plenum.

Air Sensor Potentiometer (ASP)

ASP generates a voltage signal based on position of airflow sensor plate. ECU uses this signal to enrich air/fuel ratio during cold engine acceleration.

Knock Sensor (KS)

KS consists of a piezoelectric crystal encased in a metal and plastic housing. Vibrations in engine cause crystal to generate small amounts of voltage. This voltage signal is used by ECU to determine necessary timing retardation.

Oxygen Sensor (O2)

The O2 sensor is a heated type sensor that measures oxygen content of exhaust gases. ECU uses data from O2 sensor to adjust fuel delivery. The O2 sensor is located in the exhaust system just ahead of catalytic converter.

Coolant Temperature Sensor (CTS)

The CTS is located in the cylinder head coolant passage and informs ECU of engine operating temperature. This signal is used to provide corrections to air fuel mixture, depending on coolant temperature.

Throttle Switches

Idle switch and full throttle switch provide throttle position data to ECU. Throttle switches are located on throttle body. Idle switch is closed when throttle plates are closed and opens when throttle opens approximately one degree. Idle switch signal determines operation of idle stabilizer valve. Full throttle switch closes at about 10 degrees before full throttle. Full throttle switch signal determines full throttle enrichment.

Ignition Distributor

Ignition distributor is a Hall Effect type with no centrifugal or vacuum advance. Voltage signal from Hall sender is received by ECU for engine RPM input and crankshaft position for ECU control of ignition timing.

Scheme 2

Canister Shutoff Solenoid

Shutoff solenoid valve is de-energized when engine is turned off. This closes purge line between carbon canister and intake, preventing fuel vapors from collecting in intake system.

When engine is started, canister shutoff solenoid is energized, allowing stored vapors to be purged from canister. Canister shutoff solenoid is located on top of carbon canister.

Cold Start Valve

Cold start valve injects extra fuel into intake manifold during cold starts. Cold start valve is controlled by FICU. Operation of valve is determined by coolant temperature to prevent excess fuel from being injected. Cold start valve is located on back of intake manifold.

Differential Pressure Regulator

Differential pressure regulator is attached to fuel distributor and controls fuel flow in lower chamber of fuel distributor. This helps to control fuel mixture. With vehicle at normal operating temperature and all engine controls functioning properly, regulator operates with current from ECU.

During full load operation, full throttle switch closes, sending a signal to ECU. ECU sends a signal approximately 3 mA greater than signal that is currently present. This signal will vary, depending on engine speed and altitude.

When vehicle is decelerated, fuel to injectors is shut off by reversing current to -50 mA to -60 mA. Engine speed at which this reversing will take place is regulated by coolant temperature.

Idle Stabilization Valve

Idle stabilization valve consists of a rotary valve and a return spring attached to an armature. Valve controls idle speed. Varying amounts of DC voltage sent by ECU cause motor to pull against return spring allowing air to by-pass throttle plate.

Idle speed is maintained between 650-790 RPM on warm engines and at about 1000 RPM for cold engines. With this system, no idle speed adjustments are necessary or possible. Idle stabilization valve is located between intake air boot and intake manifold.

Ignition Coil

Ignition coil is equipped with a power stage mounted on the side. Power stage switches primary current in coil on and off in place of Hall Effect control unit. Power stage is controlled by signals from ECU.

TESTING PRECAUTIONS

When testing CIS Motronic system, observe following precautions to avoid injury or damage to the system.

1. DO NOT touch or disconnect ignition wires with engine running. Disconnect or connect engine wiring and test leads ONLY with ignition off. DO NOT disconnect battery with engine running or apply voltage to control units.
2. If engine must be turned over but not started, remove and ground coil wire. A fast charger can be used as a starting aid for no more than 15 seconds at a time with a one minute break between attempts and a maximum of 16.5 volts.

ENTERING DIAGNOSTIC MODE

The ECU will store faults for self-diagnosis. The ECM has a permanent fault code memory (50 states and Calif.), as well as a temporary fault code memory (Calif. only). When ECU detects a temporary fault, the "FAULT INDICATOR LIGHT" (FIL) on the instrument panel will flash. The FIL will continue to flash until ignition is turned off. The ECU may clear the fault on next engine start, and the FIL will not flash unless fault is detected again. Vehicle will have to be test driven for at least 5 minutes to reset fault. When ECU detects a permanent fault, FIL will flash but fault will remain in ECU memory until physically erased.

Fault will be displayed by a flashing LED in tester. Connect LED Tester Tool (part number US 1115 or equivalent) to battery positive terminal and test connector No. 1. Access fault codes by inserting a fuse into top of fuel pump relay for 4 seconds, then remove fuse. Diagnostic terminals will be grounded and ECU memory will display any fault code via a flashing sequential code LED Tester Tool. (Scheme 3)and (Scheme 4).

Only one fault will be displayed and that fault code will be repeated until fuse is reinserted in fuel pump relay for 4 seconds and removed. Now the next stored fault code will be displayed. Continue with fuse insert/remove procedure until a Code 0000 is displayed indicating all fault codes have been displayed. Code 0000 is read when LED Tester Tool is lit for 2.5 seconds, then off 2.5 seconds, and continues this display with no pause in flashing.

Scheme 3

Scheme 4

CLEARING FAULT CODES

Turn ignition off. Connect LED Tester Tool (part number US 1115 or equivalent). Insert fuse in fuel pump relay. Turn ignition on and remove fuse after 4 seconds. LED Tester Tool should switch off, then start flashing a Code 0000. Insert fuse in fuel pump relay for 10 seconds, then remove fuse. LED Tester Tool should not be flashing. If LED Tester Tool is still flashing a code, repeat procedure.

FAULT CODES

FAULT CODE

Scheme 5

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 5) 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»(/audi/80/b3-1986-1991/remont/testing-diagnostics/#bosch-cis-motronic-system) chart. (Scheme 6) If system electrical tests are okay, replace ECU. Clear fault codes.

Scheme 6

CIS-MOTRONIC VOLTAGE & RESISTANCE TESTS

DECELERATION FUEL SHUTOFF

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 5) 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»(/audi/80/b3-1986-1991/remont/testing-diagnostics/#bosch-cis-motronic-system) chart. (Scheme 6) If system electrical tests are okay, replace ECU. Clear fault codes.

Scheme 7

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 7)
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 8

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 8)
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. (Scheme 9) 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 9

Scheme 10

Scheme 11

1. Ensure engine is at normal operating temperature. Connect Test Adapter (VW1501 ) between potentiometer and harness. (Scheme 10) 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 11) 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. 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.

OXYGEN SENSOR

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 5) 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 12

1. This check is necessary only if no ignition spark is present. Remove harness connector from output stage of ignition coil and connect LED Tester (US1115 ) to terminals 2 and 3. (Scheme 12)
2. Crank engine and observe LED light on tester. If LED flickers, Hall Effect sensor is okay.
3. If LED does not flicker, remove harness connector from Hall Effect sensor on distributor. Connect multimeter to outer connections of harness connector. Turn on ignition. Voltage to Hall Effect sensor from ECU should be 9 volts minimum. If voltage is low, check battery, battery cables, all wiring and ECU.

Scheme 13

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 13)
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. 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 5) 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 7)
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.

RESIDUAL PRESSURE

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.

COOLANT TEMPERATURE 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.

Scheme 14

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 14)
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.

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). If resistance is as specified, check full throttle switch.

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.

ADJUSTMENTS

See appropriate article in TUNE-UP PROCEDURES section.

Audi 80 2.0L Wiring Diagram. Scheme 15

See also:
• CIS-MOTRONIC VOLTAGE & RESISTANCE TESTS