Self Diagnosis - Theory & Operation (N12): Diagnosis MINI Cooper I

DIAGNOSTIC TROUBLE CODE INDEX

DIAGNOSTIC TROUBLE CODE INDEX (N12)

3 Diagnosis of the canister purge valve

(P0441)

The diagnoses of the canister purge valve consist of a canister load check and an active check that utilizes the tank leakage diagnostic module described in the corresponding section of this document. The canister load check by itself cannot detect a malfunction of the canister purge valve but it can be deduced from this check that the canister purge valve isn't faulty.

In the active check phase, which is enabled independent of whether the load check was performed or not, the canister purge valve is commanded to open and a pressure build is induced in the tank with an electric pump. This pressure can be calculated from the current of the electric pump. The tightness of the tank system, an open CPV is here treated as a leakage, is determined by comparing this current with that of the pump current obtained during a reference leak measurement. A malfunction of the canister purge valve is implied when the difference doesn't exceed a calibrated threshold.

4 Diagnosis of evaporative system with DM-TL

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

The DM-TL ( D iagnostic M odule T ank L eakage) 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 102) 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 102

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 103): Purge Mode.

Scheme 103

For a reference current measurement the air pump's motor is switched on (Scheme 104) 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 104

In the Monitoring Mode (Scheme 105) 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 105

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 air flow

(P115C, P115D)

7 Diagnosis of mass airflow sensor

(P0100; P0102; P0103; P113A, P113B, P115A, P115B)

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

8 Diagnosis of fuel system

(P2187, P2188; P2177; P2178)

This diagnosis is able to analyze up to two fuel systems, each with its own fault paths. In case of a stereo system with two fuel systems, each fuel system is monitored separately but all in the same way.

The detailed error paths of this diagnosis are not illuminating the MIL but the general failure path FMAS. The handling of the general failure path FMAS is described in an additional document.

8.3 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 rkat or frau or frao are enabled depending on the operating area see scheme 24 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. To avoid misdetections, the result of the diagnosis is delayed when the car is running out of fuel. For this purpose, a specific function for a near empty fuel tank is performed.

9 Front oxygen sensor's heater control diagnosis

(P3016; P0135 P03026)

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 106)below.

Scheme 106

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

10.1.1 Offset diagnostic via the lambda controller function - shift to leaner region

A maximum fault PLLSUmax will be set after a calibrated delay time, if the monitoring conditions are fulfilled and the integral component of the secondary lambda controller is greater than the calibrated maximum threshold value.

10.1.2 Offset diagnostic via the lambda controller function - shift to richer region

A minimum fault PLLSUmin will be set after a calibrated delay time, if the monitoring conditions are fulfilled and the integral component of the secondary lambda controller is less than the calibrated minimum threshold value.

14 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 107) 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 107

16 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.

19 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 108) 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 108

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 109) 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 109

20.1 Diagnosis during cold start

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.

22 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.

24 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.

25 Diagnosis of intake air temperature sensor

(P0113, P0112, P111E, P0111, P105D)

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

27 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.

28 Diagnosis of pressure differential sensor

(P1197, P1198, P1124, P1104, P1105)

The diagnosis of the pressure-differential sensor is able to detect electrical faults as well as a wrong connected or defect sensor. All relevant checks are carried out continuously.

28.2 Offset diagnosis

The average pressure of the pressure differential sensor is calculated continuously. A fault counter is incremented when this calculated average pressure exceeds a calibrated threshold during ignition off.

If the fault counter exceeds a calibrated threshold, a DDSSSig fault will be set.

29 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.

30 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 timer signal check and a rationality check. The free running timer is used to determine the engine off time.

31 Diagnosis of crankshaft signal

(F0335, 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.

32 Offset diagnosis of camshaft position

(P1338, P1339)

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.

33 Diagnosis of camshaft position sensor

(P0340; P0341, P0342, P0365, P0366, P0367)

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.

35 Diagnosis of the knock sensor line

(P0327; P0328)

36 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.

Scheme 110

37 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.

39 Diagnosis of the sensor's voltage supply

(P0641, P0651, P0697)

The CY320 integrated circuit has 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.

40 Diagnosis of system voltage

(P0687)

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

41 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 fault will be set.

42 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

45 Diagnosis of CAN data bus - TCM communication

(P3214; U0101; U1202)

46 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, P0013, P2090, P2091, P0201, P0202, P0203, P0204, P0261, P0264, P0267, P0270, P0262, P0265, P0268, P0271)

48.1.1 Diagnosis of a leakage in the system

A disconnection or leakage in the PCV-System results in a reaction within the intake air charge determination system (deviation between modeled and measured intake air mass flow).

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

Scheme 111

Scheme 112