Main Relay Failure Symptoms
An open circuit in the Main Relay will result in no voltage to the EMS2000 and the other components as supplied by the Main Relay.
A permanently engaged Main Relay will result in an excessive closed current draw and will lead to a dead battery.
Main Relay activation is monitored by the EMS2000. Faults will be set if the main relay is energized and power is not received by the EMS2000.
Main Relay Testing
- Check Voltage Supply At Battery
- Test for Voltage at Fuse 34 (With key on)
- Check Voltage at KL 30 of Main Relay
- Check operation of Relay (Using relay adapter) Ground signal from EMS2000 Voltage Drops across Relay (Relay Energized and Not Energized)
- Perform TEST PLAN on Power Supply
Scheme 31
Scheme 32
TMap and MAP Sensors Failure Symptoms
- Engine difficult to start, stalls at idle and misfires.
TMap and MAP Sensor Testing
- Check status on DISplus status pages (0 - 5 volts) Ensure that voltage changes and does not remain constant at 0 or 5 volts
- Install BOB on EMS2000 check voltage at appropriate pins
- Check sensor for internal shorts
- Perform TEST PLAN
Intake Air Temp Sensor Failure Symptoms
- Problems with cold starting, poor driveability and an increase in emissions.
- Possible lack of power, particularly noticeable in hot ambient temperatures.
Note. With other possible failure modes the EMS2000 should ensure that the engine will limp home on a default value.
Intake Air Temp Sensor Testing
- Check status on DISplus status pages (0-5 volts). Ensure that voltage changes and does not remain constant at 0 or 5 volts.
- Check Sensor Resistance
- Perform TEST PLAN
Workshop Hint MAP and TMAP Sensors
- Voltage Reading of approx. 1-2 volts indicates high vacuum condition (Idle or no load)
- Voltage Reading of 4-4.8 volts indicates low vacuum condition (Full Throttle)
Workshop Hint Air Inlet Temp Sensor
- Workshop Hint MAP and TMAP Sensors Voltage Reading of 1 volt indicates warm air temperature
- Voltage Reading of 4 volts indicates cold air temperature
Notes
Coolant Temperature Sensor Failure Symptoms
- The vehicle may be difficult to start, may run lean when the engine is cold or slightly rich when the engine is hot (default to 'emergency program' mode).
- Driveability of the vehicle will be affected.
- If the sensor output signal fails open, shorted to ground, shorted to 12V or shorted to 5V the EMS2000 will replace the temperature value with a default value.
- If the sensor ground is shorted to 12V or shorted to 5V, temperature gauge will go to full hot and engine cooling fan goes to high when fault is recognized.
Coolant Temperature Sensor Testing
- Check status on DISplus status pages (0 - 5volts) Ensure that voltage changes and does not remain constant at 0 or 5 volts
- Check Sensor Resistance
- Perform TEST PLAN
Scheme 33
Diagnosis
During cranking the digital signal produced by the sensor is sent to the EMS2000. The EMS2000 expects to receive a signal of 58 targets and two missing targets. If this signal is received the EMS2000 will synchronize itself to the engine. (The EMS2000 knows crankshaft position.) In the event a faulty or improper signal is received the EMS2000 will not begin or allow injection or ignition.
There is no crankshaft back up facility on the EMS2000 because the camshaft sensor target only produces one pulse per revolution.
Failure of the camshaft sensor will set a fault. Testing of the sensor is done through the test plan and the measurement system.
Camshaft sensor failure will cause the injection system to default into a semi-sequential mode.
Note. The EMS2000 can utilize the crankshaft sensor signal as a backup if the camshaft sensor fails.
Knock Sensor Fault Symptoms
- The EMS2000 will not be able to detect and correct for engine knock resulting in a "pinging" sound within the engine.
- The engine will lack power and fuel consumption will be affected.
- The knock strategy ensures that the engine defaults to a safe ignition value.
LDP System (Leak Diagnosis Pump) Reed Switch
Vapors containing Hydrocarbons form in the vehicles fuel tank and to prevent them from venting to atmosphere, legislation in the USA demands on-board monitoring of the fuel system sealing on all vehicles powered by an Internal Combustion engine. Beginning with Model Year 2000 these regulations were tightened, and call for detection of a 0.5 mm (0.02 inch) leak.
- The EVAP system used on the MINI will be the Siemens Leak Detection Pump (LDP). The LDP system is located above the right rear inner fender liner.
The LDP is an electrically/vacuum-actuated device that will pressurize the evaporative emission system for the purpose of detecting leaks and verifying canister purge valve integrity. It has an integrated Canister Vent Valve (CVV) that controls the atmospheric venting of the fuel vapor storage canister.
The LDP assembly is only replaceable as a complete unitized component, however, it is separate from the charcoal canister.
The upper chamber contains an integrated reed switch that produces a switched high/low voltage signal that is monitored by the EMS2000. The switch is opened by the magnetic interruption of the metal rod connected to the diaphragm when in the top dead center position. The repetitive up/down stroke is confirmation to the EMS2000 that the valve is functioning and the basis for determining if a leak is present in the system.
The EMS2000 monitors the length of time it takes for the reed switch to open, which is opposed by pressure under the diaphragm in the lower chamber. If this component or its circuits are defective, a fault code will be set and the "Malfunction Indicator Light" will illuminate when the OBD II criteria is achieved.
Scheme 34
Scheme 35
O2 Sensor Failure Symptom(s)
- If the upstream sensor fails it may result in poor performance and rough idle.
- Poor emissions control will cause the MIL to illuminate.
- As soon as the EMS2000 has detected an upstream oxygen sensor failure, it will default the fuel control to open loop operation.
- Slow response of sensor due to ageing or possible contaminated sensor tip.
Brake Light Switch Fault Symptoms
If the two brake signals are seen to be inconsistent at any time, a fault condition must be assumed. The accelerator pedal activation signal is set to zero, hence there will be no throttle demand and the engine will remain at idle. If this occurs while in a cruise active mode, the system shall suspend and will disable cruise for the remainder of that journey. The system will register a fault disallowing further operation.
Injector Testing
Fuel Injectors can leak and bleed off fuel pressure causing hard or long starting and increased emissions. Injectors are leak tested using the Fuel Injector Leakage Tester.
Injectors should also be tested using the DISplus for
- Resistance (approximately 12W)
- Power Supply (B+ from Main Relay)
- Status Request - Fuel Injection Signal (approximately 3.0 ms - 5.0 ms)
- EMS2000 final stage activation (see graph)
Scheme 36
Note. Measurement is performed on the negative B- side of injector or trigger pin of EMS2000. Vehicle voltage is present when injector is not active. EMS2000 pulls voltage to ground causing injector to open. When EMS2000 releases ground, injector closes and a voltage spike is produced because of the collapsed coil winding of injector.
Ignition Coil Testing
Ignition system faults may be diagnosed with the DISplus or GT1 if equipped with a Measurements Interface Box. Enter the test plan for ignition coil (a choice of four coils, 1, 2, 3, or 4 will be given). The oscilloscope will be pre-set during the test plan.
When measuring kV on cylinders 1 and 2, remember that the voltage is flowing from the outer electrode to the center and back to the coil. This will be indicated by negative voltage readings on the oscilloscope. kV's on cylinders 1 and 2. The voltage will be approximately 20% higher than on cylinders 3 and 4.
Note. Secondary output in the 7- 9 kV range are normal during firing of the cylinder on the compression stroke and 3 - 5 kV for the cylinder on the wasted spark stroke. A defective coil will influence two cylinders, a defective plug wire only influences one cylinder.
Federal Test Procedure (FTP)
The Federal Test Procedure (FTP) is a specific driving cycle that is utilized by the EPA to test light duty vehicle emissions. As part of the procedure for a vehicle manufacturer to obtain emission certification for a particular model/engine family the manufacturer must demonstrate that the vehicle(s) can pass the FTP defined driving cycle two consecutive times while monitoring various components/systems.
Some of the components/systems must be monitored either once per driving cycle or continuously. Systems and their components required to be monitored once within one driving cycle
- Oxygen Sensors
- Catalyst Efficiency
- Evaporative Vapor Recovery System Due to the complexity involved in meeting the test criteria within the FTP defined driving cycle, all tests may not be completed within one "customer driving cycle". The test can be successfully completed within the FTP defined criteria, however customer driving styles may differ and therefore may not always monitor all involved components/systems in one "trip". Components/systems required to be monitored continuously
- Cylinder Misfire Detection
- Fuel system
- Oxygen Sensors
- All emissions related components/systems - EMS or EML (comprehensive component monitoring).
The graph shown below is an example of the driving cycle that is used by BMW to complete the FTP.
Scheme 37
The diagnostic routine shown above will be discontinued whenever
- Engine speed exceeds 3000 RPM
- Large fluctuations in throttle angle
- Road speed exceeds 60 MPH
Note. The driving criteria shown can be completed within the FTP required approximately 11 miles in a controlled environment such as a dyno test or test track.
Every time the vehicle is started a drive cycle resumes from where it left off. Depending on the customers driving habits, they might never reach a FTP.
A "customer driving cycle" may vary according to traffic patterns, route selection and distance traveled, which may not allow the "diagnostic trip" to be fully completed each time the vehicle is operated.
OBD II Diagnostic Trouble Codes (DTC)
The Society of Automotive Engineers (SAE) established the Diagnostic Trouble Codes used for OBD II systems (SAE J2012). The DTC's are designed to be identified by their alpha/numeric structure. The SAE has designated the emission related DTC's to start with the letter "P" for Powertrain related systems, hence their nickname "P-code".
Scheme 38
- DTC's are stored whenever the "Malfunction Indicator Light" is illuminated.
- A requirement of CARB/EPA is providing universal diagnostic access to DTC's via a standardized Diagnostic Link Connector (DLC) using a standardized tester (scan tool).
- DTC's only provide one set of environmental operating conditions when a fault is stored. This single "Freeze Frame" or snapshot refers to a block of the vehicles environmental conditions for a specific time when the fault first occurred. The information which is stored is defined by SAE and is limited in scope. This information may not even be specific to the type of fault.