Engine Controls - Basic Diagnostic Procedures BMW Z4 E85/E86

INTRODUCTION

Note. Vehicles are equipped with an OBD-II diagnostic system. For thorough and complete diagnosis, manufacturer strongly recommends the purchase of BMW-specific diagnostic equipment. For diagnosis, see 2002 SELF-DIAGNOSTICS , 2003 SELF-DIAGNOSTICS - Except 7-Series or 2003 SELF DIAGNOSTICS - 7-Series article.

The following diagnostic steps will help prevent overlooking a simple problem. This is also where to begin diagnosis for a no-start condition. The first step in diagnosing any driveability problem is verifying the problem with a test drive under the conditions the problem reportedly occurred.

Before entering self-diagnostics, perform a careful and complete visual inspection. Most engine control problems result from mechanical breakdowns, poor electrical connections or damaged/misrouted vacuum hoses. Before condemning the computerized system, perform each test listed in this article.

Note. Perform all voltage tests with a Digital Volt-Ohmmeter (DVOM) with a minimum 10-megohm input impedance, unless stated otherwise in test procedure.

DISCONNECTING & CONNECTING BATTERY

Turn ignition off. If ignition is not turned off when battery is disconnected, fault memories can be set in some control units. If there is a possibility of mixing up battery leads (if battery positive and negative leads are the same color) and you are in doubt, follow the polarity to the battery and then mark and cover leads. Radio codes must be re-entered after battery is disconnected. Be sure to ask customer for their radio code card beforehand. Make a note of stored transmitters and restore these transmitters after reconnecting battery. Stored settings of on-board computer and clock will also be lost. All available keys must be recorded for cars with first generation infrared transmitter locking systems.

Do not disconnect battery and leads from alternator and starter motor while engine is running. Detach terminal of battery negative lead from car battery and second battery if fitted. Cover battery negative terminal(s). Detach terminal of battery negative lead from car battery and second battery if fitted. Cover battery negative terminal(s). When work is carried out on electrical system, faults may be caused in memories of some control units when battery is connected.

After connecting battery, initialize sunroof of vehicles with a 2-battery system. The 2-battery system has a starter battery circuit and a system battery circuit. A supplementary control unit monitors both battery circuits. Depending on the situation, battery circuits are connected to or isolated from supplementary control unit via an isolating relay. Two batteries are used as a storage battery. These batteries must not under any circumstances be charged with a voltage in excess of 14.8 volts. Rapid charging must not be used.

DISCONNECTING & CONNECTING ECM/DME CONTROL MODULE

Disconnecting vehicle battery will cancel fault memories of control units. Before disconnecting battery, always read out fault memories. Investigate stored faults and, once any faults have been remedied, cancel fault memory. Control unit connectors should only be connected and disconnected while ignition is turned off. Removal and installation of components, relays, fuses, and other components can cause faults to be stored in fault memories capable of self diagnosis. Always interrogate fault memories after completing work on electrical system. Investigate stored faults and, once any faults have been remedied, cancel fault memory. If replacing ECM, always read out hardware/software version of corresponding control unit with BMW DIS tester. Comply with instructions of DIS tester for coding and programming.

On vehicles with electronic vehicle immobilization, follow instructions of DIS tester. Each control unit is programmed with certain basic values, which serve as mean values. Control unit receives different input values, depending on engine condition, which are compared with stored values. Adaptive system compares input values with stored map values. Control commands are routed to relevant actuators. If, for example, DME control unit was without current for a long time (more than an hour), its adaptive system would lose stored values. When a cleared control unit is restarted or a new control unit is installed, adaptive system must read and store input values of associated engine as new basic values. If not performed, this could lead to erratic idling and disturbed overrunning of engine after starting. Depending on engine, it could require some time before all values are adapted to engine condition.

Observe following procedure before replacing or reinstalling a control unit: If possible before exchanging control unit, run engine up to operating temperature. Remove control unit. Install a new control unit and operate vehicle at different engine speeds.

STARTING AID

Do not start engine with use of starting sprays. When starting engine with jumper wires, ensure jumper lead wires are appropriate size. Only use fuse-protected jumper leads. Check whether current supplying battery is 12 volts. If engine is started from battery of another vehicle, ensure there is no contact between bodies of both vehicles. Never touch ignition system components and current. If battery in vehicle supplying power is weak, start engine and run at idle. Always confirm with the procedures to avoid injury to persons or damage to parts.

On automatic transmission, select Park setting and apply hand brake. On manual transmission, move shift lever into neutral and apply parking brake. Ensure jumper leads cannot get caught in rotating parts such as cooling fan.

Connect positive terminals of both batteries with one jumper lead (Red). Use positive connection point in engine compartment for vehicles with one battery in trunk. Then attach second jumper lead (Black) to negative terminal of donor battery and to engine or body ground on vehicle to be started. Never connect second jumper lead (Black) to negative terminal of battery in vehicle to be started. This would produce explosive gas which could be ignited by sparks. After engine of vehicle to be started has started, first disconnect jumper lead on negative terminal/ground connection. Then remove jumper lead from positive terminals.

VISUAL INSPECTION

Visually inspect all electrical wiring, looking for chafed, stretched, cut or pinched wiring. Ensure electrical connectors fit tightly and are not corroded. Ensure vacuum hoses are properly routed and are not pinched or cut. Inspect air induction system for possible vacuum leaks.

Compression (6-Cylinder & V8)

1. Deactivate fuel injection system by removing Digital Motor Electronics (DME) master relay and fuel pump relay before performing compression test. See «DME & FUEL PUMP RELAY LOCATION»(/bmw/z4/e85e86-2002-2005/remont/testing-diagnostics/#engine-controls-basic-diagnostic-procedures) table. Ensure battery is fully charged.
2. Ensure engine coolant temperature does not exceed 86°F (30°C). Remove oil filler cap. Remove 2 nut covers and nuts securing cylinder head cover(s). Remove cylinder head cover(s). Disconnect ignition coil connectors.
3. Remove ignition coils. Using 16-mm Socket (12-1-171) and Torque Limiter (12-1-172), remove spark plugs. Use Pressure Gauge (11-0-162), Test Adapter (11-0-166) and Tube Extension (11-0-167) to check compression pressure. See «COMPRESSION SPECIFICATIONS»(/bmw/z4/e85e86-2002-2005/remont/testing-diagnostics/#engine-controls-basic-diagnostic-procedures) table. DME & FUEL PUMP RELAY LOCATION (1) Application Location 3-Series Z3 DME Relay Right Rear Corner Of Engine Compartment, Next To DME ECU Fuel Pump Relay Under Left Side Of Instrument Panel, Next To Kick Panel Z4 DME Relay Left Rear Corner Of Engine Compartment, In Relay/ECU Box Fuel Pump Relay Under Right Side Of Instrument Panel, Behind Glove Box E46 DME Relay Left Rear Corner Of Engine Compartment, In Relay/ECU Box Fuel Pump Relay Behind Glove Box 5-Series & Z8 DME Relay Right Rear Corner Of Engine Compartment, Next To DME ECU Fuel Pump Relay Right Side Of Trunk (1) For illustrated relay location, see «RELAYS & SOLENOIDS»(/bmw/z4/e85e86-2002-2005/remont/testing-diagnostics/#engine-controls-system-component-testing) in SYSTEM & COMPONENT TESTING article. COMPRESSION SPECIFICATIONS Application Specification Compression Pressure 6-Cylinder 142-156 psi (10-11 kg/cm 2 ) V8 170-199 psi (12-14 kg/cm 2 )

Compression (V12)

Compression on V12 engine can only be checked with a BMW-specific Diagnosis and Information System (DIS). Remove engine cover. Remove spark plug from 12th cylinder. (Scheme 1) Connect DIS tester. Connect charger. Call up diagnosis on DIS tester. Follow DIS tester instructions. A mechanical compression pressure check is not possible.

Scheme 1

Exhaust System Backpressure

The exhaust system can be tested with a vacuum or pressure gauge. If using a pressure gauge, remove HO2S or air injection check valve (if equipped). Connect a 0-5 psi pressure gauge and run engine at 2500 RPM. If exhaust system backpressure is greater than 2 psi, exhaust system or catalytic converter is plugged.

If using a vacuum gauge, connect vacuum gauge hose to intake manifold vacuum port. Start engine. Observe vacuum gauge. Open throttle part way and hold steady. If vacuum gauge indication slowly drops after stabilizing, inspect exhaust system for restriction.

FUEL SYSTEM PRESSURE RELEASE

Wrap a rag around fuel line. Open fuel line slowly.

FUEL PRESSURE TEST

Note. For information on testing individual fuel system components, see FUEL SYSTEM in SYSTEM & COMPONENT TESTING article.

General Information

1. The connection for the vacuum hose of the fuel pressure regulator is located between the throttle and the air cleaner or on the air cleaner. As a test precondition, ensure the correct fuel pressure regulator is fitted. Using the Pressure Testing Kit (135220), check whether the fuel pressure regulator suitable for the car is installed. See «FUEL VOLUME & PRESSURE»(/bmw/z4/e85e86-2002-2005/remont/testing-diagnostics/#engine-controls-basic-diagnostic-procedures__fuel-volume-pressure) .
2. The control function of the fuel pressure regulator must be guaranteed under all operating conditions. The fuel pump must always be able to generate a higher fuel pressure than the pressure regulated by the pressure regulator. The injection rate is adjusted by means of the injection time; the injection time is controlled by the Digital Motor Electronics (DME) control module.
3. When the engine is at a standstill and the ignition key is in off position, the fuel return line after the pressure regulator is at zero pressure.
4. The pressure regulator closes when the engine is at a standstill and the ignition key is in off position. The fuel pressure in the delivery line is retained over an extended period. A non-return valve closes in the fuel pump. These measures help to retain the fuel pressure in the fuel system. Extended starting times are thus avoided.

Fuel Pressure Related Problems

1. Drive Characteristic Faults, Lack Of Power: Run engine at idle speed and measure fuel pressure. If measured value is less than the nominal value of - 2.9 psi (- 0.2 bar), line cross-sections in fuel feed are constricted or fuel filter is clogged, or fuel pump voltage supply is not okay because of possible high contact resistance (corrosion) in plug connection between wiring harness and fuel pump. If the measured value is greater than the nominal value of 2.9 psi (0.2 bar), turn off engine and then observe measured value. If measured value drops to nominal value, then line cross-sections in fuel return are constricted or clogged. Check fuel lines for kinks. It no kinks are visible, replace return lines. If measured value remains too high, then pressure regulator is in all probability faulty. NOTE: It is less likely that return line may be completely blocked. When pressure regulator is removed, fuel could escape under pressure. Have a clean cloth ready and catch and dispose of escaping fuel. Replace return line but not the pressure regulator.
2. Starting Problems: Run engine briefly at idle speed, then switch off. Note measured value while engine is stopped. Read off measured value again after about 20-30 minutes while engine is stopped. If the measured value has dropped by more than 7.2 psi (0.5 bar), start engine and wait briefly for a stable pressure increase. Switch off the engine and immediately pinch off the delivery line just before the pressure gauge with Hose Clamp (133010). Note measured value. Read off measured value again after about 20-30 minutes while engine is stopped. If measured value has now dropped by less than 7.2 psi (0.5 bar), the following faults can be present: Fault in delivery lines. Fault in in-tank delivery hose. Faulty pressure-holding non-return valve in fuel pump. Check components and replace as necessary.
3. If the measured value has dropped by more than 7.2 psi (0.5 bar) again, replace pressure regulator. All fuel hoses and hose clips which were detached within the framework of the checks must be replaced. Interrogate fault memory of DME control unit. Check for stored fault messages. Rectify faults and clear fault memory.

Oscilloscope Pattern

Evaluate ignition voltage peaks in response to sudden accelerator loads. Voltage peak No. 1 indicates dying-out process is not much higher than ignition voltage peak. Ignition system is okay. If beginning of dying-out process is considerably higher than ignition voltage peak as is shown in voltage peak No. 2, there is a fault in injection system such as lean mixture, defective injection valve or low compression. (Scheme 2)

Scheme 2

FUEL VOLUME & PRESSURE

Note. The following procedure is for 6-cylinder engines, and may apply to other engines.

Begin basic fuel system diagnosis by determining fuel system pressure.

1. Remove engine cover to gain access to fuel lines. Prepare Pressure Testing Kit (135220) which consists of Check Valve (135221) and Adapter (135222). Remove dust cap from measuring valve on fuel rail. Connect check valve and gauge to fuel rail. Block (plug) fuel return line with Fuel Hose Clamp (133010).
2. Remove fuel pump relay. See «DME & FUEL PUMP RELAY LOCATION»(/bmw/z4/e85e86-2002-2005/remont/testing-diagnostics/#engine-controls-basic-diagnostic-procedures) table. Using Fuel Pump Relay Bridging Caliper (613050) or jumper wire, connect terminals No. 87 and 30 at fuel pump relay socket. (Scheme 3) This will turn fuel pump on.
3. Disconnect fuel return line. Install extension hose and hold end of hose in Graduated Glass Container (133020). Check fuel pump delivery rate. See «FUEL PUMP PERFORMANCE»(/bmw/z4/e85e86-2002-2005/remont/testing-diagnostics/#engine-controls-basic-diagnostic-procedures) table. FUEL PUMP PERFORMANCE Application Pressure psi (kg/cm 2 ) Min. Vol. In 30 Sec. Pts. (L) 6-Cylinder & V8 50 (3.5) 1.85 (0.9) V12 (1) (1) (1) Information is not available.

Fuel Pump Relay

Note. If relay does not work on vehicle, check battery feed, DME relay, PCM and ground circuits at fuel pump relay.

Remove fuel pump relay. Apply battery voltage to relay terminal No. 30 and terminal No. 86. (Scheme 3) Ground relay terminal No. 85. Voltage should now exist at relay terminal No. 87. Replace relay if it does not work as indicated.

Scheme 3

SERVICING PRECAUTIONS

Note. For location of DME and fuel pump relays, see DME & FUEL PUMP RELAY LOCATION table under PRELIMINARY INSPECTION & ADJUSTMENTS.

1. Ensure ignition is turned off before working on the ignition system. The engine may not be started without a connected secondary circuit. When checking compression, remove Digital Motor Electronics (DME) master relay.
2. DO NOT connect shielded capacitors to terminal No. 1 of the ignition coil. DO NOT connect terminal No. 1 of the ignition coil to ground or battery positive terminal, as this will damage ignition stages in DME control unit.
3. DO NOT connect DVOM or test light to terminal No. 1 of ignition coil while engine is running. High tension (350 volts) is present at coil terminal No. 4, secondary ignition leads, spark plugs and ignition coil terminal No. 1 to DME control unit.

Oscilloscope Pattern Diagnostics

1. Evaluate sparking period and ignition voltage peaks at idle. Voltage peak No. 1 indicates normal combustion period. Voltage peak No. 2 indicates normal ignition voltage peak. Ignition system is okay. (Scheme 4)
2. If scope indicates a long sparking period (voltage peak No. 1) with ignition voltage (voltage peak No. 2), low compression is present. If sparking period is fluctuating, spark plug is fouled. (Scheme 5)
3. A short sparking period (voltage peak No. 1) with high ignition voltage peak (voltage peak No. 2) or a constant but short sparking period, indicates a defective ignition lead. (Scheme 6)
4. During evaluation of ignition voltage peaks and attenuation process at idle, if scope indicates a beginning of attenuation process with normal peaks upwards and downwards (voltage peak No. 1), or attenuation process is greatly shortened (voltage peak No. 2), ignition coil is defective. If there is an absence of initial downwards attenuation (voltage peak No. 3), ignition coil is defective. (Scheme 7)
5. During evaluation of sparking voltage at idle, normal combustion period is indicated by voltage peak No. 1. Normal attenuations to sparking voltage line is indicated by voltage peak No. 2. Ignition coil is okay. (Scheme 8) If shorter sparking period is indicated (voltage peak No. 1) or attenuation to sparking voltage line is only slight (voltage peak No. 2), ignition coil is defective. (Scheme 9) If sparking period is much shorter (voltage peak No. 1) or attenuation to sparking voltage line is absent (voltage peak No. 2), ignition coil is defective. (Scheme 10) If there is no sparking voltage line, ignition coil is defective. (Scheme 11)
6. During evaluation of combustion voltage line at a raised engine speed, voltage peak No. 1 indicates normal combustion period. Voltage peak No. 2 indicates normal attenuations to sparking voltage line. Ignition coil is okay. (Scheme 12) A shorter sparking period (voltage peak No. 1) and if attenuations to sparking voltage line is only slight (voltage peak No. 2), then ignition coil is defective. (Scheme 13) If combustion period (voltage peak No. 1) is normal or attenuations to sparking voltage line are absent (voltage peak No. 2), ignition coil is defective. (Scheme 14)

Scheme 4

Scheme 5

Scheme 6

Scheme 7

Scheme 8

Scheme 9

Scheme 10

Scheme 11

Scheme 12

Scheme 13

Scheme 14

Oscilloscope Pattern Diagnostics (Various Coil Manufacturers)

If vehicle is equipped with Bremi, Beru, May and Christe or Bosch coil, evaluate ignition voltage peaks and decay characteristics at idle speed. (Scheme 15) To evaluate combustion voltage characteristics at increased engine speeds of approximately 2500 RPM (Scheme 16)- (Scheme 19).

Scheme 15

Scheme 16

Scheme 17

Scheme 18

Scheme 19

Scheme 20

Scheme 21

Scheme 22

Scheme 23

1. For evaluation of sparking period at idle, voltage peak No. 1 indicates normal ignition voltage peak. Spark plug is okay. If ignition voltage peak (voltage peak No. 2) is low, electrode gap is small. If ignition voltage peak (voltage peak No. 3) is high, electrode gap is too large. (Scheme 20)
2. For normal combustion and spark plug (Scheme 21) If combustion period is long, electrode gap is small. (Scheme 22) If spark period is short, electrode gap is large. (Scheme 23)

Ignition Voltage

See IGNITION VOLTAGE CHECK table.

IGNITION VOLTAGE CHECK

IDLE SPEED & IGNITION TIMING

Idle speed and ignition timing are not adjustable. For further information, see ON-VEHICLE ADJUSTMENTS article. See IDLE SPEED table.

IDLE SPEED

See also:
• 2003 SELF-DIAGNOSTICS - Except 7-Series
• RELAYS & SOLENOIDS
• ON-VEHICLE ADJUSTMENTS
• DME & FUEL PUMP RELAY LOCATION
• FUEL VOLUME & PRESSURE