Self Diagnosis - Theory & Operation (N14): Diagnosis MINI Cooper I

DIAGNOSTIC TROUBLE CODE INDEX

DIAGNOSTIC TROUBLE CODE INDEX (N14)

3 Diagnosis of the canister purge valve

(P0441)

The canister purge valve (CPV) diagnosis is capable of detecting a CPV which is controllable, with a maneuverability that lies above an applicable threshold, as well as a CPV which is stuck open or stuck close. The underlying principle is the comparison of the engine's torque when the CPV is closed with the engine's torque when the CPV is fully open. The CPV monitor consists of an active and a passive check.

Scheme 158

4 Diagnosis of evaporative system with DM-TL

(P1449, P1448; P1447, P1434, P0442, P0456)

The DM-TL (Diagnostic Module Tank Leakage) is used for monitoring the evaporative system for small (> 0.02 in) and rough (> 0.04 in) leaks.

It consists of an electrically driven air pump, a change-over valve and a 0.02 inch orifice for reference measurement - (Scheme 159) The tightness of the tank system is obtained by comparing the actual air pump's motor current with that measured when the system is operated with a standardized reference orifice.

Scheme 159

When the air pump is switched off the fuel tank breathes through the charcoal canister, the changeover valve and the air filter. For canister purging, the purge control valve is opened and fresh air flows via the air filter, the change-over valve and the charcoal canister into the intake manifold - (Scheme 160)

Scheme 160

For a reference current measurement the air pump's motor is switched on (Scheme 161) for a short period of time while the change-over and purge control valves are closed. The air pump's motor current is measured while fresh filtered air is being pumped through the 0.02 inch reference orifice.

The diagnosis is aborted when at some unusual operating conditions the motor current doesn't stabilize. To prevent a permanent disablement of the leak check due to a malfunction of the diagnostic module (DM-TL), the number of consecutive irregular current measurements is counted and a module error DMTL is set as soon as a calibrated value is reached.

Scheme 161

In the Monitoring Mode (Scheme 162) the change-over valve is switched on while the purge control valve remains closed. The motor current drops to a zero-load level. Fresh air is now pumped through the charcoal canister into the tank. A small overpressure, indicated by an increase in the motor current, builds up if the evaporative system is tight.

Scheme 162

5 Diagnosis of fuel level sensor (FLS)

(P144A, P144B, P0462, P2067, P0460 P2065, P0461, P1409, P1433)

The diagnosis of the fuel level sensor signal, which is received via CAN bus, consists of electrical checks and a plausibility check.

The following fault codes are used

P144A Range check

P144B Plausibility check

P0461 Stuck check

P0462 FSTEmin, P2067 FSTESmin Electrical error Fuel Level Sensor 1/2

P0460 FSTEmax P2065 FSTESmax Electrical error Fuel Level Sensor 1/2

P1409 FSTEsig, P1433 FSTESsig CAN signal check

The diagnosis of the signals of the two fuel level sensors consists of the following checks.

6 Diagnosis of mass airflow sensor (MAF)

(P115A, P115B, P115D)

7 Diagnosis of mass airflow sensor

(P0100, P0102, P0103, P113A, P113B)

The diagnosis of the mass airflow sensor (MAF sensor) consists of the following checks.

8 Diagnosis of leakage of intake manifold

(P1497)

For this diagnosis it is possible to exploit the advantages of the air mass sensor and the intake manifold pressure sensor by adaptation of the modelled pressure to the measured intake manifold pressure.

The modeled manifold absolute pressure based on the mass airflow sensor is adapted (corrected) with help of the measured values of the manifold absolute pressure sensor. After a certain "enable time" the adaptation is considered to be stable and the difference between the measured and modeled manifold pressure should be very small.

If, after this "enable time", the difference between measured and modeled manifold absolute pressure exceeds a calibrated threshold for a calibrated period of time, a leakage of the intake manifold is detected and a plausibility fault LSZR will be set.

9 Diagnosis of fuel system

(P2187, P2188, P2177, P2178)

9.3 Fuel system diagnosis

The diagnosis of the fuel system checks the output values of the fuel trim adaptation described before. Above a temperature limit the adaptation of the integrator frai or ora are enabled depending on the operating area see scheme 25 All integrator output values are compared to their calibrated upper and lower limits. If the integrator output reaches one of the limits after the adaptation has stabilized, a malfunction is detected, the engine conditions are stored and a corresponding fault is set.

10 Front oxygen sensor heater control diagnosis

(P3016, P0135, P3026)

Internal heating is required when the heat dissipated from the exhaust gas isn't sufficient to maintain the oxygen sensor at its operating temperature. The required extra heating power depends on the deviation from the operating temperature. It can be controlled by varying the duty cycle factor of its heater - (Scheme 163)below.

Scheme 163

A malfunction is implied when in spite of maximum heating power the temperature of the galvanic (or Nernst) cell of the sensor stays below its operating point. A reliable galvanic cell temperature determination is ascertained by referencing a calibration resistor.

The front oxygen sensor's control diagnosis consists of the following checks

15 Diagnosis of the evaluation IC of the front oxygen sensor

(P3012, P3014, P3024, P3022, P2626, P3018, P3020, P2237, P0132, P0131, P2243, P2251)

The Diagnosis of the evaluation IC (CJ125) of the front oxygen sensor detects electrical faults of the VM (virtual ground), UN (Nernst voltage), IA (compensation) and IP (pump) signal lines - (Scheme 164) These electrical faults could result from short circuits and signal interruptions. Short circuits are detected by a self-diagnosis of the CJ125. Line interruptions are identified by observing the system. The diagnosis monitors communication between the CJ125 IC and the powertrain control module and also performs a rationality check of the supply voltage as well as the adaptation values of the IC's electrical compensations. The evaluation IC's diagnosis runs continuously.

Scheme 164

17 Diagnosis of the heating of the rear oxygen sensor

(P0141)

The temperature dependent internal resistance of the rear oxygen sensor's galvanic (or Nernst) cell is influenced by electrical heating and the heat dissipated from the exhaust gas. The effect of a change in the heating power and/or a change in the exhaust gas temperature on the internal resistance is noticeable only after a delay time. The internal resistance will be unusually high if the heater is defective.

20 Thermostat diagnosis

(P0128)

The main function of the thermostat is to allow the engine to heat up quickly and then maintain it at its operating temperature. The thermostat achieves this by regulating the amount of engine coolant that flows through the radiator - (Scheme 165) At low temperatures the thermostat completely blocks the inlet of the radiator forcing all of the coolant to be recirculated via the engine block. It then progressively opens, allowing the engine coolant to flow through the radiator, when the temperature rises past the optimum at which engine operation results in lesser pollutants and lesser mechanical wear.

Scheme 165

The warming up of the engine coolant during a cold start at low ambient temperatures will be delayed if a malfunction of the thermostat left it stuck open or when the thermostat is completely missing. A warm up delay means emissions relevant functions and diagnosis that depend on the engine coolant temperature, will be executed only after a delay or might not be executed at all. The thermostat diagnosis runs once per driving cycle when all monitoring conditions are fulfilled and is capable of detecting a delay in the warming up (faulty thermostat) of the engine coolant by comparing the measured with the modeled engine coolant temperatures - (Scheme 166) A rationality fault THMnpl is set when the modeled temperature less the measured temperature is greater than a modeled-temperature-dependent calibrated value for a calibrated period of time.

Scheme 166

21.1 Diagnosis during cold start (catalyst heating)

During cold start (catalyst heating) it is checked whether there is a permanent deviation between the current idle speed and the setpoint idle speed. Additionally it is necessary to take into account the condition of the ISC integrator.

The ISC integrator is a measurement for the regulated deviation to reach the setpoint idle speed and is limited to an upper and lower limit.

If the throttle valve opens too much it may happen that the idle speed rises above the fuel cut-off engine speed and the system starts oscillating. To cover this special case the number of detected fuel cut-offs during an idle phase is analyzed.

If

1. the deviation (positive) between setpoint and current idle speed (underspeed) exceeds a calibrated threshold and
2. the ISC integrator equals the upper maximum threshold and
3. the engine load lies below a calibrated threshold

all for a calibrated period of time, a malfunction is detected and a minimum fault LLRKHmin fault is set.

If

1. the deviation (negative) of the current engine idle speed lies below a calibrated threshold and
2. the ISC integrator equals the new lower threshold limit and
3. no fuel cut-off condition has been detected

all for a calibrated period of time, a malfunction is detected and a LLRKHmax fault is set.

If the number of detected fuel cut-offs during this idle phase exceeds a calibrated threshold for a calibrated period of time, a malfunction is detected and a LLRKHmax fault is set.

23 Diagnosis of throttle body

(P1634, P1631, P1635)

During the software adjustment phase of the powertrain control module to the mechanical throttle body characteristics, the following checks are performed.

25 Diagnosis of Accelerator Pedal Position Sensor

(P2122, P2123, P2127, P2128, P2138)

The accelerator pedal consists of two independent sensors (S1 and S2), which supply the accelerator pedals angle. The function that provides the relation between the voltage drop across the sensor and the corresponding relative accelerator pedal position or angle is stored as a characteristic curve in the powertrain control module.

The diagnosis monitors the accelerator pedal's angle by employing both sensor voltages. When monitoring conditions are fulfilled, the diagnostic starts by performing a range check for both sensor signals.

A maximum fault is set when S1's voltage and/or S2's voltage each exceeds their corresponding maximum calibrations for a calibrated period of time. If no maximum fault is detected, a synchronization check will be performed.

A minimum fault is set when the difference between S1 and S2's voltages lies above a calibration and S1's voltage and/or S2's voltage lies below its/their corresponding calibrations for a calibrated period of time.

A plausibility fault will be set after a calibrated period of time when no minimum faults are detected in spite of the difference between S1 and S2's voltages lying above calibration.

Scheme 167

26 Diagnosis of the engine coolant temperature (ECT) sensor

(P0118, P0117, P112B, P0116)

The diagnosis of the engine coolant temperature sensor (ECT sensor) consists of circuit continuity and rationality checks of the coolant temperature behavior.

27 Diagnosis of intake air temperature sensor

(P0113, P0112, P105D, P111E, P0111)

The diagnosis of the intake air temperature sensor consists of a circuit continuity check and rationality checks of the intake air temperature behavior.

29 Diagnosis of atmospheric pressure sensor

(P2228, P2229, P321E, P321F, P323C, P322A)

The diagnosis of the atmospheric pressure sensor consists of a circuit continuity check, a range check and a rationality check of the given output voltage of the sensor. The output voltage of the sensor can directly be calculated into the absolute atmospheric pressure.

30 Diagnosis of manifold absolute pressure sensor

(P1250, P1255, P0107, P0108, P129D, P129E)

The diagnosis of the manifold absolute pressure sensor (MAP sensor) consists of a circuit continuity check, a range check and a rationality check of the given output voltage of the sensor. The output voltage of the MAP sensor can directly be calculated into the absolute pressure.

31 Diagnosis of pressure sensor upstream throttle valve

(P0237, P0238, P12A0, P12A1, P12A2, P12A3)

The diagnosis of the pressure sensor in front of the throttle valve consists of a circuit continuity check, a range check and a rationality check of the given output voltage of the sensor. The output voltage of the sensor can directly be calculated into the absolute pressure.

32 Diagnosis of the vehicle speed

(P0503, P0500, P152B, P0501)

The diagnosis of the vehicle speed consists of a range check, a stuck check and a rationality check of the vehicle's speed signal.

33 Diagnosis of engine off time

(P1515, P1551)

The diagnosis of a free running externally clocked time, which is received via CAN bus, consists of a CAN timersignal check and a rationality check. The free running timer is used to determine the engine off time.

34 Diagnosis of crankshaft signal

(P0335, P0336)

This diagnosis monitors, whether a plausible crankshaft signal is present, how is its quality procured and whether a gap must be identified on this signal.

35 Offset diagnosis of camshaft position

(P1338)

The offset angle diagnosis offers two different services to avoid inadmissible exhaust gas emissions or engine damage caused by camshaft to crankshaft misalignment. This check continuously measures the offset angle to monitor if the change in the camshaft position reaches the calibrated threshold that represents the exceedance of permissible exhaust emission. The offset angle is calculated from the difference between the set and the measured position of equidistant edges. If the calculated value lies beyond a calibrated range, a EpmCaSI1OfsErr fault will be set.

With this diagnosis it is possible to analyze the proper alignment of 2 inlet and 2 outlet camshafts, each with its own fault path. In case of a system with more than one alignment check, each check is done separately but all in the same way.

36 Diagnosis of camshaft position sensor

(P0340, P0341, P0342)

The diagnosis of the camshaft sensor monitors the level of the phase sensor signal. The diagnosis has to detect a missing camshaft signal and a disturbed camshaft signal respectively.

37 Diagnosis of variable valve timing

(P0012, P000A)

The inlet camshaft diagnosis of the variable valve timing monitors continuously whether the commanded valve timing is achieved by position and in time.

38 Diagnosis of the knock sensor line

(P0327, P0328)

39 Diagnosis of Knock Sensor

(P0327, P0328)

The knock sensor diagnostic detects a faulty or bad connected sensor and by the response of this diagnosis it is also possible to deduce engine damage. An enlarged piston groove for example leads to an increase in the noise level.

The diagnosis starts by calculating a reference signal based on the knock sensor's signal. This reference signal represents the basic noise of the current cylinder being analyzed. Given all monitoring conditions are fulfilled, a KS1Min or KS1Max fault will be set after a calibrated number of consecutive samplings if the calculated reference signal respectively lies below a calibrated minimum or above a calibrated maximum - see figure below.

Scheme 168

40 Diagnosis knock detection signal evaluation

(P0324)

The status word of the signal evaluation function is constantly monitored to check if the current integration result is invalid. The number of occurred faults is stored in a counter. The result is checked at the end of the monitoring time frame. If the number of faults exceeds a calibrated threshold, a DKRSA fault will be set. The measuring window is monitored in the same way. If the timing and length of the measuring window does not lie within an expected range, the fault counter will be incremented. If the number of faults exceeds a calibrated threshold, which indicates a false measuring window, a DKRSA fault will be set.

41 Diagnosis of power stages of high pressure injection valves

(P3100, P3104, P3108, P3112, P3101, P3105, P3109, P3113, P3102, P3106, P3110, P3114, P3103, P3107, P3111, P3115, P3149, P3152, P3155, P3158, P3150, P3153, P3156, P3159, P3148, P3151, P3154, P3157, P16A5)

The power stages of the high pressure injection valves are incorporated in the engine control unit (ECU) and they include a built in hardware diagnosis. A high voltage (about 65V) is required to open the injection valve. It is provided by a so called "high side". Additionally every injection valve needs a dedicated selection line for operation. This selection line is realized with a so called "low side".

Scheme 169

42 Diagnosis of High Pressure Fuel Control System

(P1216, P3007, P3091)

For gasoline direct fuel injection a high pressure fuel control system is necessary for fuel preparation and metering (Scheme 170) The low fuel pressure from the fuel pump module within the tank is increased by the high pressure fuel pump and adjusted to a desired set-point fuel pressure.

The high pressure fuel system consists of a common fuel rail for all high pressure injection valves, a fuel rail pressure sensor, a high pressure fuel pump with a built-in fuel volume control valve and overpressure valve.

In dependence of torque demand and engine speed, high pressure has to be adjusted to values between 5 and 12 MPa. Therefore the fuel pressure in the rail is measured and controlled with help of the fuel volume control valve.

According to the desired fuel-pressure set-point value the pre-control calculates the driver-signal for the fuel volume control valve.

Scheme 170

43 Diagnosis of Fuel Rail Pressure Sensor

(P0190, P0192, P0087, P0088)

44 Diagnosis of the sensor's voltage supply

(P0641, P0651, P0697)

The CY320 integrated circuit possesses three different voltage supply outlets. The diagnosis of each of these voltage supplies works the same way. It detects short circuits to battery and ground. The sensor's voltage supply is monitored by a comparator circuit. If the quotient of the measured sensor supply voltage to the reference value lies outside of a defined threshold, a SSpMon1 (SSpMon2, SSpMon3) fault will be set.

45 Diagnosis of system voltage

(P0687)

The diagnosis monitors the voltage of the electric system. It consists of a range check.

46 Diagnosis of the 5V voltage supply

(P167E, P167F)

The diagnosis checks if there is the required 5V at the supply module. If the measured voltage exceeds a calibrated threshold, a MonUMaxSupply fault will be set. Likewise, if the measured voltage lies below a calibrated threshold, a MonUMinSupply faut will be set.

47 Diagnosis of Powertrain CAN A

(P3202)

A signal fault CANA will be set, if after initialization of the CAN data bus, the CAN controller reports a CAN A bus off state for a calibrated period of time

50 Diagnosis of output stages

(P0444, P0458, P0459, P2418, P2419, P2420, P2400, P2401, P2402, P0030, P0031, P0032, P0036, P0037, P0038, P0597, P0598, P0599, P0010, P2088, P2089, P0001, P0003, P0004)

52.2 Diagnosis of a leakage in the system

Low Load Tube: A disconnection or leakage in the PCV-System results in a reaction within the intake air charge determination system. There is a leakage value calculated after throttle butterfly. This is done by a comparison of the air flow (calculation via pressure before and after throttle butterfly and throttle butterfly angle) and measured intake air mass flow. When the leakage exceeds a threshold, a failure is generated.

In this case a fault code will be stored by the intake air charge monitoring system.

Scheme 171

High Load Tube: A disconnection is not possible without demolition of the concerned parts.

Scheme 172

59 Diagnostic system management

The term diagnostic system management (DSM) refers to all diagnostic functions that exist in a powertrain. The diagnostic system manager collects, processes and prepares all fault information in the standardized form for access by a generic scan tool as well as for the illumination of the malfunction indicator lamp.

Monitoring functions detect component faults which then trigger a series of reactions. (Scheme 173) depicts the order of events when a malfunction occurs in the powertrain system. The fault check status is first stored along with the appropriate error and cycle flags. An error flag that is set will influence the system functionality in a manner defined by the inhibit handler function. Faults are made available to the diagnostic interface which is accessible with a diagnostic scan tool and additionally linked, where appropriate, to the malfunction indicator lamp via the diagnostic fault even storage function.

The diagnostic system manager itself is defined mainly by the diagnostic scheduler, the diagnostic inhibit handler and the diagnostic fault event storage functions.

59.1 The diagnostic scheduler

The diagnostic scheduler is a configurable coordinator that oversees the optimal execution of diagnostic functions. It dynamically computes and assigns priorities to functions in situations where two or more functions are ready to run but physical reasons don't permit them to run simultaneously.

59.2 The diagnostic inhibit handler

The diagnostic inhibit handler is the interface to the reaction functions of the powertrain control system. It consists of an array of function identifiers that trigger system reactions which could be in the form of auxiliary functions, replacement values or even an inhibiting of the function.

59.3 The diagnostic fault event storage

The diagnostic fault event storage is essentially a memory where detected faults are stored along with freeze frames and the status for each check. Each fault check represents a symptom and is normally associated to a physical component.

Scheme 173

59.4 Diagnostic test results

This module stores the test results provided by the diagnostic functions and prepares these results for output to the diagnostic interface.

The realization of the in-use monitor performance ratio kernel function is described in the corresponding section. The configurations of the diagnostic inhibit handler and the diagnostic scheduler are also detailed in a separate section (consequential malfunctions) of this document.