Digital Control System - Turbo & Quattro Audi 5000 CS

DESCRIPTION

Audi Digital Control (DC) system uses Continuous Injection System (CIS LAMBDA) system for fuel delivery and electronic controls for mixture adjustment, emission control and ignition timing. An indicator light on the dash will illuminate if detonation continues or a fault is detected in the circuits.

The electronic controls consist of an intake manifold pressure sensor (built into the ECU), air temperature sensor, coolant temperature sensor, Electronic Control Unit (ECU), crankshaft speed sensor, crankshaft reference sensor, Hall Effect switch, knock sensor, throttle valve switch, brake switch, engine overheat sensor and oxygen sensor.

The ECU uses the inputs to control the cold start valve, oxygen sensor heater, cold engine warm-up enrichment, Lambda control (frequency) valve, transistorized ignition coil, wastegate frequency valve, charcoal canister shut-off valve, fault warning light and ignition timing control.

Scheme 35

Fuel Pump & Relay

The fuel pump assembly, located in fuel tank, is equipped with a pressure damper at the suction end. Fuel pump is activated during start-up and when engine is running. Fuel pump relay switches off fuel pump in absence of signal from ECU and provides voltage for cold start valve.

Mixture Control Unit (MCU)

Fuel is metered and delivered to individual cylinders dependent on air intake quantity which is metered by airflow sensor. For more information of the MCU, airflow sensor plate, fuel distributor, frequency valve, see DESCRIPTION & OPERATION in the CIS (LAMBDA) SYSTEM article.

Electronic Control Unit (ECU)

The ECU is located behind cover in front passenger footwell. Ambient temperature around ECU must not exceed 180°F (85°C).

With ignition switched on, ECU is connected to battery voltage. An intake manifold pressure sensor is located within the ECU. This provides the ECU with engine load information.

The ECU controls the boost pressure, fuel mixture and ignition timing based on intake manifold pressure, coolant temperature and intake air temperature. The ECU also uses signals from the throttle switch to richen the mixture during wide open throttle operation.

Cranking Enrichment

During engine cranking, a signal from the starter relay is sent to the ECU to enrich the fuel mixture. The amount of enrichment or activation of the cold start valve is controlled by the ECU based on the coolant temperature sensor.

Warm-Up Enrichment

When coolant temperature sensor indicates a cold engine, ECU adjusts the duty cycle of frequency valve to about 80%.

Oxygen Sensor

Oxygen sensor is mounted in exhaust pipe in front of catalytic converter. Oxygen sensor measures oxygen content in exhaust gas. Heating element is used to quickly warm oxygen sensor. Minimum operating temperature of oxygen sensor is 572°F (300°C). A rich mixture will send a signal in excess of .5 volt while a lean mixture will give signal of less than .5 volt.

IGNITION CONTROL

An ignition advance timing map is programmed into the ECU. The ECU will trigger the coil for base idle timing and timing advance. The actual timing advance depends on signals from the intake manifold pressure and input from ignition timing reference sensor, engine RPM speed sensor and coolant sensor.

Engine RPM Speed Sensor

An engine RPM speed sensor, located in the upper part of bell housing, detects movement of ring gear teeth on the flywheel. This signal is used to determine engine RPM and ignition timing point.

Ignition Timing Reference Sensor

This sensor is located next to the engine RPM speed sensor. It detects the rotation of a pin located 60 degrees BTDC. This sensor sends a signal to the ECU when TDC occurs for number one and number 4 cylinder. The Hall Effect switch, located in the distributor, produces only one signal for each revolution of the distributor. This signal occurs just before TDC of number one cylinder. This signal is used to determine which signal from the ignition timing reference sensor is the actual TDC signal for number one cylinder. DO NOT rotate distributor to set base timing.

Knock Sensor

The knock sensor is mounted at the center on the left side of cylinder block. A 3-wire connector (Red) transmits signals to the ECU. The knock sensors signal will retard ignition timing in 3 steps of 2.6 degrees, up to a total of 7.8 degrees retard. When knocking stops, the ECU will advance timing in steps of 1.3 degrees, up to the point knocking started.

Idle Speed Control

Idle speed stabilizer is separate from digital control unit. The throttle switch is used to initiate idle speed control. Air control valve, located in throttle valve by-pass hose, receives signals from idle speed stabilizer.

With ignition on and engine off, air control valve is activated. This provides a valve opening which is determined by coolant temperature. After engine is started, idle stabilizer adjusts idle speed based on idle stabilizer thermo switch, throttle position, and engine RPM.

A/C operation will also send a signal to the ECU which will modify the signal to the air control valve. Engine speed is controlled by temperature from 1000 RPM at 0°F (-20°C) to low of 720 RPM at 68°F (20°C).

OTHER CONTROLS

No description of deceleration control, wastegate control or charcoal canister shut-off control is available from manufacturer.

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 SELF-DIAGNOSIS & ELECTRICAL SYSTEM TESTING in this article. Dry off tip and check for leaks. Acceptable leakage rate of cold start valve is one drip per minute or less.

Cranking Enrichment & Cold Engine Warm-Up Enrichment

For information on these systems see ELECTRICAL COMPONENTS (FUEL SYSTEM) in this article.

System Pressure

1. Connect Pressure Gauge (VW 1318 ) between line from fuel distributor to cold start valve and test port connection on lower chamber of fuel distributor, using Adapter Fittings (VW 1318/5 ). Test port is sealed by a threaded plug. Bridge fuel pump relay with Jumper Switch (US 4480/3 ).
2. Open valve on pressure gauge (points at cold start valve line when open) and activate fuel pump. System pressure must be 68-78 psi (4.7-5.4 kg/cm 2 ). If pressure reading is low and fuel pump delivery quantity is good, adjust or replace regulator assembly.
3. If pressure reading is high, disconnect fuel tank return line from fuel distributor. Repeat test. If reading is correct, check for plugged return line. If reading is incorrect with line open, replace regulator assembly.
4. If pressure is not within specification and regulator valve has been replaced, adjust system pressure at fuel distributor. Refer to SYSTEM PRESSURE in ADJUSTMENTS section of this article.

Residual Pressure & Internal Leak Testing

1. Open valve on pressure gauge. Operate fuel pump for 30 seconds. Pressure can drop to a minimum of 38 psi (2.7 kg/cm 2 ) after 10 minutes. If pressure drops below specification, inspect fuel pump check valve and all fuel fittings for leakage. NOTE: Pressure and leak testing does not include checking cold start valve.
2. If there are no leaks, check sensor plate clearance. If plate clearance is correct, replace regulator assembly and repeat leak test. If pressure drop is not within specification, replace fuel distributor "O" rings.

Main Pump Delivery Volume

1. Check transfer pump (if equipped) and fuel filter. Disconnect fuel return line and place open end in measuring container. Switch on fuel pump with jumper switch. Check fuel pump delivery volume for 30 second period.
2. Minimum delivery volume is .71 qts. (.68L) for 30 seconds with reading of 11.4 volts at fuel pump. Voltage is measured with engine off and fuel pump activated by jumper switch.

Scheme 36

1. Remove fuel pump relay, from relay panel, and install Jumper Switch (US 4480/3 ). Attach Fuel Quantity Analyzer (US 4480 ) to bumper and secure in place. Remove injectors from cylinder head with fuel lines attached. Check and replace fuel injector "O" rings as necessary.
2. Check tightness of injector insert (2-piece inserts). If inserts are loose, remove and clean threads. Use sealing compound when installing upper insert. Replace sealing washer that goes against cylinder head below lower portion of insert. Lubricate injector "O" rings with gasoline and install injectors, with fuel lines connected, into fuel quantity analyzer tubes.
3. Ensure lines are not kinked or bent. Loosen fittings to align fuel lines and retighten. Remove rubber boot from airflow sensor housing above sensor plate. Turn and lift setting screw and adjusting slide of Sensor Plate Adjustable Holder (VW 1348/1 ) into upper position. This simulates full throttle operation. (Scheme 36)
4. Place sensor plate adjustable holder on airflow sensor housing with holder centered over plate. Pointer on edge of holder base must point toward center of fuel distributor. (Scheme 36) Push adjusting slide of holder down onto stop.
5. Turn adjusting screw clockwise until magnetic end touches sensor plate retaining bolt. Activate fuel pump with jumper switch. Turn adjusting screw of holder counterclockwise until any one injector starts to deliver fuel. Turn off jumper switch and empty fuel quantity analyzer into fuel tank.
6. Idle injection quantity is measured first. Lifting adjusting slide of holder to first stop simulates idle position of sensor plate. Activate fuel pump with jumper switch until fuel level reaches 20 ml on scale of any tube for quantity comparison.
7. Check that all injectors have identical spray patterns that are even and cone-shaped. If not, raise sensor plate up quickly to full lift position and release. Repeat idle quantity test. Maximum difference in delivery quantity between injectors is 3.0 ml of fuel.
8. If fuel delivery quantity differs between high and low levels by more than 3.0 ml, interchange injectors and repeat test. If difference of delivery quantity changes with injectors, replace injectors. If difference of delivery quantity does not change with movement of injectors, either fuel lines are pinched or fuel distributor is defective.
9. Measure full throttle injection quantity. Empty analyzer into fuel tank and reinstall injectors in analyzer. Lift adjusting slide of holder to last stop to simulate full throttle position of sensor plate. Activate fuel pump with jumper switch until fuel level reaches 80 ml on scale of any tube of analyzer.
10. Check that all injectors have identical spray patterns that are even and cone-shaped. Maximum difference in delivery quantity between injectors is 8.0 ml of fuel.
11. If fuel delivery quantity differs between high and low levels by more than 8.0 ml, interchange injectors and repeat test. If difference of delivery quantity changes with injectors, replace injectors. If difference of delivery quantity does not change with movement of injectors, either fuel lines are pinched or fuel distributor is defective.
12. Check fuel injectors for leakage immediately after delivery quantity test is complete. Set sensor plate in rest position. Activate fuel pump with jumper switch for 2 minutes. Injectors should not drip. Replace injectors that do drip.

Scheme 37

1. Turn ignition on. Engine warning light (on instrument panel) should come on. Start engine. Engine warning light should go off. Drive vehicle for at least 5 minutes to store necessary information in control unit memory. During test drive, accelerate engine above 3000 RPM and briefly accelerate using full throttle. NOTE: If engine will not start, crank starter for at least 5 seconds. Return ignition key to "ON" position. Fault codes may now be read.
2. DO NOT turn ignition off as this will erase control unit memory. Install a fuse in test terminal of fuel pump relay (in fuse/relay panel) for a minimum of 4 seconds and then remove. (Scheme 37) NOTE: Careful attention must be paid to flashing light, since there are no discernible break points between 4-digit number groups.
3. Engine warning light will flash on for 2 1/2 seconds and then off for 2 1/2 seconds. Trouble codes will then be flashed as 4 digit numbers. After each flash there will be a 1/2 second pause before the next flash occurs. Adding flashes together will obtain each code digit.
4. After each digit code is flashed, there will be a 2 1/2 second pause. After fourth digit of number is flashed, a 2 1/2 second pause will follow before the fault code is repeated.
5. The fault code will be repeated until the ignition is turned off. Record fault code. Check the list of input codes and possible problems. (Scheme 38)
6. Check and repair circuits and/or sensors as indicated, see appropriate test in the ELECTRICAL COMPONENTS testing procedures in this article. After the fault is corrected, repeat step 1) and check for additional codes.

Scheme 38

Output Codes

1. Control unit circuitry allows checking of certain components by generating specific output signals. During output diagnosis, components can be checked by listening for their operation. Diagnostic output code will flash during testing, indicating which step control unit is in.
2. Turn ignition switch off to erase fault memory. Turn ignition on. DO NOT crank or start engine. If this is done, system will automatically switch to input testing when diagnostic procedure has been activated.
3. To activate diagnostic procedure, insert spare fuse into fuel pump relay (in fuse/relay panel) for 4 seconds and then remove. (Scheme 37) This will activate the first of 5 output steps. To proceed to the next step, reinstall fuse in fuel pump relay for 4 seconds and then remove.
4. First step (Code 4433) will activate fuel pump. Pump will continue to activate throughout all 5 steps and until diagnostic procedure is ended by turning off ignition.
5. Second step (Code 4441) will operate OXS frequency valve at 50% duty cycle until next step is activated.
6. Third step (Code 4442) will cause wastegate frequency valve to switch on and off until next step is activated.
7. Fourth step (Code 4443) will cause cold start valve to switch on and off for about 10 seconds.
8. Fifth step (Code 4343) causes carbon canister shut-off valve to switch on and off until step is terminated by turning ignition switch off. If necessary, output tests may be continued by repeating steps 3) through 8) or cancelled by removing fuse.
9. If any device does not operate as indicated during output tests, see appropriate test in the following ELECTRICAL COMPONENTS testing procedures.

ECU Voltage Supply

1. Unplug ECU harness connector. Connect voltmeter positive test lead to pin No. 35. (Scheme 40) 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.

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 39)
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 39

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 40) 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 40) If no continuity, check for an open circuit in wire.

Cold Start Valve Operation (Code 4443)

1. Disconnect harness connector from cold start 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 4443 appears, LED test light must be on. If light is on, replace cold start valve.
3. If light did not come on, ensure 12 volts are present between cold start 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 about.2 ohms in wire between ECU terminal No. one and cold start valve terminal No. 2. (Scheme 40) If ohms are not as specified, check for an open circuit in wire. If circuit is not open, replace ECU.

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.

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.

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 40) If ohms are not as specified, check for an open circuit in wire. If circuit is not open, replace ECU.

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.

OXS Frequency Valve (Code 4441)

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 4441 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 40) If ohms are not as specified, check for an open circuit in wire. If circuit is not open, replace ECU.

Scheme 40

1. Remove control unit panel located on passenger side footwell. Unplug ECU connector. Turn ignition on. Using a voltmeter, check voltage between terminals No. 35 and 18, and between terminals No. 35 and 9. (Scheme 40) Voltmeter reading should be close to 12 volts.
2. Turn ignition off. Connect voltmeter between terminals No. 32 and 9. Turn ignition on and apply brake pedal. Voltmeter reading should be close to 12 volts. Turn ignition off. If readings are incorrect, check for open circuit in brake light wiring. If wiring is okay, replace brake light switch.

Tachometer Signal Output

1. Peel back ECU connector boot. Attach a voltmeter positive lead to ECU terminal No. 7. Attach negative lead to any good ground. Start engine and check for a steady voltage increase as RPM is increased.
2. If engine does not run, check engine speed sensors. If engine runs, but voltage does not increase, replace ECU. If voltage increased, but vehicle tachometer did not respond, check wiring between ECU terminal No. 7 and tachometer. If okay, repair or replace tachometer.

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 41) 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 40)and (Scheme 41). Ensure each wire between ECU and sensor connectors has zero ohms of resistance. See ENGINE SPEED SENSOR CIRCUITS chart. ENGINE SPEED SENSOR CIRCUITS Sensor Terminal Connector Terminal Engine RPM (Gray) 1 29 2 11 3 28 Ignition Timing Reference (Black) 1 13 2 12 3 28
4. Ensure clearance between ignition timing reference sensor and flywheel pin is.43" (1.10 mm) If engine speed sensors and wiring circuits are okay, replace control unit.

Scheme 41

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.

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.

Coil Resistance Check

Using ohmmeter, check ignition coil primary and secondary resistance. Disconnect coil primary and secondary ignition leads. Connect ohmmeter leads across primary terminals No. 1 and 15 at coil. (Scheme 43) Resistance value should be.5-1.5 ohms. Connect ohmmeter leads between positive terminal (No. 1) and coil high voltage tower. (Scheme 42) Secondary resistance value should be 5000-9000 ohms. If resistance values are not to specification, replace ignition coil.

Scheme 42

Scheme 43

1. Check Blue wire from terminal No. 1 of ignition coil to power transistor for any damage. Repair if necessary. Remove secondary ignition wire from coil tower. Using a jumper wire, connect coil tower wire to ground.
2. Disconnect power transistor connector (next to ignition coil). Connect voltmeter between terminal No. 1 (Green/White wire) and ground. (Scheme 43) Install a jumper wire between terminal No. 2 (Brown/White) and ground. NOTE: Ensure test lead connections are correct. If reversed, ECU will be damaged.
3. Crank engine. Ensure voltmeter reading is.20 volts minimum. If reading is incorrect, check wiring between switching module and control unit connector as follows.
4. Unplug ECU connector. Using an ohmmeter, check continuity between terminal No. 2 of ECU connector and terminal No. 2 of power transistor connector.
5. Also check continuity between ECU connector terminal No. 22 and terminal No. 1 of power transistor connector. (Scheme 40) Ohmmeter reading should be close to zero ohms for both tests. If not, check for open circuit between ignition control unit and switching module. If wiring is okay, replace ECU.

Spark Plug Wires & Rotor

1. Check coil wire resistance. If radio suppression wires are used, reading should be 1200-2800 ohms. If not, reading should be zero ohms.
2. Check resistance of spark plug wires. If radio suppression wires are used, reading should be 4600-7400 ohms. If not, reading should be 600-1400 ohms. Check spark plug connectors. If radio suppression connectors are used, reading should be 4000-6000 ohms. If not, reading should be 600-1400 ohms.
3. Check rotor and spark plug wire distributor cap connectors. Resistance should be 600-1400 ohms. Ensure rotor is marked "R1".

Throttle Valve Switch

See ADJUSTMENTS in this article for checking and adjusting procedure for idle and full throttle valve switches.

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.

Charcoal Canister Shut-Off Valve (Code 4442)

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.

Wastegate Frequency Valve (Code 4442)

1. If wastegate frequency valve did not click during self-diagnosis, go to step 3). If it did click, disconnect harness connector from wastegate frequency valve. Using a LED Test Light (US 1115 ), connect Red lead to Blue/Black wire and Black lead to Yellow wire.
2. Start and idle engine. Unplug throttle switch. Using a jumper wire, briefly short across throttle switch terminals No. 2 and 3. (Scheme 44) LED test light must be on for about 2 seconds or flicker. Remove jumper wire from throttle switch.
3. Disconnect harness connector from wastegate frequency valve. Using a LED Test Light (US 1115 ), connect Red lead to Blue/Black wire and Black lead to Yellow wire.
4. Perform output code self-diagnosis as previously described. When code 4442 appears, LED test light must be on or flicker. If light is on, replace wastegate frequency valve.
5. If light did not come on, ensure 12 volts are present between wastegate frequency valve Blue/Black wire and ground. If necessary, repair wiring or circuits.
6. If 12 volts are present, turn ignition off. Disconnect ECU harness connector. Check for 0.2 ohms in wire between ECU terminal No. 19 and wastegate frequency valve Yellow wire. (Scheme 40) If ohms are not as specified, check for an open circuit in wire. If circuit is not open, replace ECU.

Scheme 44

Temperature Safety Switch

1. Wastegate frequency valve must be okay before testing temperature safety switch. Disconnect harness connector from wastegate frequency valve. Using a LED Test Light (US 1115 ), connect Red lead to Blue/Black wire and Black lead to Green/Yellow wire.
2. Start and idle engine. Unplug throttle switch. Using a jumper wire, briefly short across throttle switch terminals No. 2 and 3. (Scheme 44) LED test light must be on for about 2 seconds. Remove jumper wire from throttle switch. If LED test light did not come on, replace temperature safety switch.
3. If LED test light came on, disconnect plug from temperature safety switch. Using a jumper wire, connect terminal R to ground. (Scheme 45) Using a jumper wire, briefly short across throttle switch terminals No. 2 and 3. (Scheme 44) LED test light must NOT be on or flash.
4. If not as specified, check circuits between temperature safety switch and ECU.

Scheme 45

Boost Pressure Indicator

1. Start and idle engine. Using a voltmeter, probe back side of ECU connector terminal No. 17. (Scheme 40) If voltage is not.25-2.5 volts, replace ECU.
2. If okay, check boost pressure gauge. If it does not indicate correct pressure, check wiring between ECU and instrument panel. If wiring okay, replace boost pressure gauge.

Note. CIS (LAMBDA) fuel injection maintains constant fuel pressure throughout system. Relieve pressure before opening system. DO NOT allow fuel to leak on engine or electrical parts. DO NOT allow any open flame near fuel system being serviced.

Centering Sensor Plate & Lever

1. Check sensor plate for centered position in airflow sensor housing. If plate binds on housing or is off-center, remove 6 mm bolt holding plate to lever. Coat bolt with locking compound and install finger tight.
2. Use Centering Gauge (US 1109 ) or .004" (.10 mm) feeler gauges to set plate equidistant from sensor housing. If plate cannot be centered, remove airflow sensor housing to center sensor lever.
3. Turn housing upside-down and remove bolt clamping counterweight to sensor lever. Coat bolt with locking compound and install finger tight. Center sensor plate lever in housing and tighten clamping bolt. Complete centering of plate.

Sensor Plate Rest Position

Upper edge of sensor plate must be below lower edge of sensor cone .070-.080" (1.80-2.10 mm). If rest position is incorrect, raise sensor plate. Open or close wire clip to change position of sensor plate. DO NOT bend leaf spring.

THROTTLE VALVE HOUSING

Note. Stop screw is set by manufacturer and should not be moved.

Scheme 46

Throttle Switch

1. Disconnect throttle switch harness. Attach ohmmeter to switch terminals No. one and 2. (Scheme 46)
2. Ensure throttle is set at a idle position. Ohmmeter must read zero ohms. If not, loosen mounting screws and adjust switch.

Fuel Pressure

1. Check and note existing pressure. Remove pressure regulating valve from fuel distributor.
2. Adjust pressure by changing shims in shim stack. Add shims to raise system pressure. Remove shims to lower system pressure.
3. A shim change of .020" (.5 mm) will change system pressure approximately 4.2 psi (.3 kg/cm 2 ). Ensure any replacement shims are identical in diameter to existing shims.

Scheme 47