Engine Controls - Basic Diagnostic Procedures BMW X5 E53

INTRODUCTION

Note. Vehicles are equipped with an OBD-II diagnostic system, with an OBD-II Data Link Connector (DLC). See SELF-DIAGNOSTICS 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.

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

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/x5/e53-1999-2003/remont/testing-diagnostics/#engine-controls-basic-diagnostic-procedures) table. Ensure battery is fully charged. 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 E46 DME Relay Left Rear Corner Of Engine Compartment, In Relay/ECU Box Fuel Pump Relay Behind Glove Box 5-Series & 7-Series (2) DME Relay Right Rear Corner Of Engine Compartment, Next To DME ECU Fuel Pump Relay Right Side Of Trunk (1) For illustration of relay location, see «RELAYS»(/bmw/x5/e53-1999-2003/remont/testing-diagnostics/#engine-controls-system-component-testing__relays) under RELAYS & SOLENOIDS in SYSTEM & COMPONENT TESTING article. (2) V12 vehicles use 2 DME relays.
2. Ensure engine coolant temperature does not exceed 95°F (35°C). Turn 2 fasteners on electric lead cover 90 degrees and remove electric lead cover. Repeat for other cover on V8 engines. Disconnect spark plug connectors.
3. Using 16-mm Socket (121171) and Torque Limiter (121172), remove spark plugs. Use Pressure Gauge (110162), Test Adapter (110166) and Tube Extension (110167) to check compression pressure. See «COMPRESSION SPECIFICATIONS»(/bmw/x5/e53-1999-2003/remont/testing-diagnostics/#engine-controls-basic-diagnostic-procedures) table. 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 ) V12 142-170 psi (10-12 kg/cm 2 )

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

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 1)

Scheme 1

FUEL SYSTEM PRESSURE RELEASE

Fuel system pressure release procedure is not available from manufacturer. It may be possible to remove fuel pump relay, start engine and run engine until fuel pressure drops (engine stalls). See DME & FUEL PUMP RELAY LOCATION table.

FUEL VOLUME & PRESSURE

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/x5/e53-1999-2003/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 2) 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/x5/e53-1999-2003/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 50 (3.5) 2.3 (1.1)

Fuel Pump Relay

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

Remove fuel pump relay. Apply battery voltage to relay terminal No. 30 and terminal No. 86. (Scheme 2) Ground relay terminal No. 85. Voltage should now exist at relay terminal No. 87. Replace relay if it does not work as indicated.

Scheme 2

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 3)
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 4)
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 5)
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 6)
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 7) 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 8) 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 9) If there is no sparking voltage line, ignition coil is defective. (Scheme 10)
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 11) 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 12) 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 13)

Scheme 3

Scheme 4

Scheme 5

Scheme 6

Scheme 7

Scheme 8

Scheme 9

Scheme 10

Scheme 11

Scheme 12

Scheme 13

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 14) To evaluate combustion voltage characteristics at increased engine speeds of approximately 2500 RPM (Scheme 15)- (Scheme 18).

Scheme 14

Scheme 15

Scheme 16

Scheme 17

Scheme 18

Scheme 19

Scheme 20

Scheme 21

Scheme 22

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 19)
2. For normal combustion and spark plug (Scheme 20) If combustion period is long, electrode gap is small. (Scheme 21) If spark period is short, electrode gap is large. (Scheme 22)

Ignition Voltage

See IGNITION VOLTAGE CHECK table.

IGNITION VOLTAGE CHECK

Direct Ignition System (DIS)

Measure primary coil resistance between terminal No. 1 and terminal No. 15. (Scheme 23) Secondary coil resistance cannot be measured. See IGNITION COIL RESISTANCE table.

Scheme 23

IGNITION COIL RESISTANCE - Ohms @ 68°F (20°C)

Distributor Ignition System (V12)

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

Switch off ignition. Remove distributor cap with ignition wiring harness. See REMOVAL, OVERHAUL & INSTALLATION article. Perform resistance measurement on individual components. See DISTRIBUTOR SPECIFICATIONS table. Check distributor rotor and distributor cap for hairline cracks and traces of scorching. If any are present, establish the cause and replace corresponding component.

DISTRIBUTOR SPECIFICATIONS

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

SUMMARY

If no faults were found while performing BASIC DIAGNOSTIC PROCEDURES, proceed to SELF-DIAGNOSTICS article. If no hard codes are found in self-diagnostics, or vehicle does not have a self-diagnostic system, proceed to TROUBLE SHOOTING - NO CODES article for diagnosis by symptom (i.e., ROUGH IDLE, NO START, etc.), or intermittent diagnostic procedures.

See also:
• RELAYS
• WIRING DIAGRAMS
• REMOVAL, OVERHAUL & INSTALLATION
• ON-VEHICLE ADJUSTMENTS
• TROUBLE SHOOTING - NO CODES
• DME & FUEL PUMP RELAY LOCATION