Obd-Ii & Emissions - Overview (W10, W11): Other MINI Cooper I

Sensor Electrical Check

The purpose of this monitor is to diagnose the analogue input signal from the coolant temperature sensor (TCO).

The output from the coolant temperature sensor is compared to a calibrated maximum and minimum value. If it is less than the minimum value then the error 'short circuit to ground' is declared. If the sensor output is greater than the maximum value then the error 'short circuit to battery or line break' is declared.

Sensor Low Sided Rationality Check

The purpose of this monitor is to detect a stuck low measured coolant temperature sensor signal.

After start, a model coolant temperature is calculated based on coolant temperature at start, engine speed, load while running and time spent in idle and fuel shut-off.

After a variation of the model coolant temperature the system verifies if a minimum variation of the measured coolant temperature has also occurred.

If the measured coolant temperature has not increased by the minimum value a failure is declared.

Sensor High Sided Rationality Check

The purpose of this monitor is to detect a stuck high measured coolant temperature sensor signal.

After start the difference between maximum and minimum measured coolant sensor values is calculated.

A failure is declared if the value of difference between maximum and minimum measured coolant sensor values does not exceed a threshold after the vehicle has been

1. Driven for a minimum period with engine speed, mass airflow and vehicle speed above minimum thresholds
2. At idle below a maximum vehicle speed, or in fuel cut for minimum period

Measurement Phase

The algorithm is based on the period measurement (starting from lean to rich sensor transition). To avoid non-representative measurement, the period is valid only if the sensor has been below a low threshold and above a high threshold between 2 consecutive lean/rich transitions.

Scheme 228

Detection

The rough road detection function is used by evaporative system leak detection (section 21) and misfire (section 22) monitors.

Rough road conditions must be detected to prevent erroneous misfire detection.

Furthermore, this function is used to temporarily inhibit the evaporative system leak detection function, because a rough road creates fuel slosh, which may result in errors in the evaporative leak measurement.

Leak detection

The leak detection is performed by means of two main phases

1. Tank system over-pressurizing
2. Leak magnitude measurement

During the leak detection, the canister purge valve and the canister vent valve (CVV) are closed.

The ECU (Engine Control Module) causes the pump to cycle for a fixed number of strokes. As air is drawn from outside and pumped into the fuel tank system, the system pressure increases.

Once the tank system over-pressure phase is finished the leak measurement phase starts. The diaphragm stroke is limited by the top of the diaphragm chamber and by a position defined by a reed switch level. If the tank pressure drops below a certain value, the LDP will perform a pump stroke in order to maintain the over-pressure in the tank system. Thus the time between pump strokes is an indication of the system tightness.

If there is a leak, the cycling time stabilizes at a rate, which compares to the leakage loss.

If there is no leak in the system the cycling time becomes longer.

Canister purge valve check

When the tank system is tight or the leak measured is smaller than a defined threshold the canister purge valve is checked. The purge valve is opened and each time the reed switch level is reached the TLDP performs a pump stroke in order to maintain the pressure in the tank system.

If the canister purge valve is not blocked the cycling time becomes shorter. In this case the purge valve operates correctly (not stuck or blocked).

If the canister purge valve is blocked in a closed position or if the tube between the canister and purge valve is pinched, the cycling time remains long.

Evaporative System Monitoring RBM Summary

The performance ratio for the Evaporative system monitoring for 0.5 mm leak detection will be tracked and reported to a Generic Scan tool (GST) using Mode 09 Info Type 08 Position 8. The performance ratio target for MY06 is 0.1.

Measurement principle

The misfire detection is based on crankshaft acceleration monitoring using crankshaft position measurement. The acquisition of the segment period is performed through an angular range of 180° crank angle. The segment starts NC_MIS_PHA°CA before TDC.

Scheme 229

Misfire induces a decrease of the instantaneous engine speed and thus a variation in the segment period. The misfire detection is based on monitoring for this variation of segment period.

Each segment is measured and an engine roughness value computed, this calculated value is compared with a threshold, which depends on the running conditions (air load, engine speed, coolant temperature) and flywheel adaption. If the engine roughness is above the computed threshold and there is no fade-out detected (minimum mass air flow load or rough road) and the ignition and injection are declared "correct" then a misfire is detected.

Fault processing

Emission increase (CARB B1 and CARB B4)

During the first 1000 engine revolutions, the sum of all detected misfires is calculated. If the sum of all the misfire detected at the end of the first 1000 engine revolutions is above a threshold, then a CARB B1 fault is detected.

After the first 1000 engine revolutions, the same process is used during the complete drive cycle. If at least 4 periods of misfires above threshold are recorded, then a CARB B4 fault is detected.

Catalyst damage (CARB A)

For each individual misfire detected, a weighting factor is applied depending on the running conditions (engine load and engine speed). The sum of the weighting factor adjusted misfires is computed during 200 engine revolutions. At the end of this period, a FTP cycle recognition is performed. If the sum of the weighting factor adjusted misfires is above a threshold and a FTP cycle not recognized, then a CARB A fault is detected. If a FTP cycle is recognized and if 3 periods of sum of weighting factor adjusted misfires above the threshold are recorded, then a CARB A fault is detected.

Limitation of this strategy

To ensure reliable misfire detection, phenomenon that may result in false misfire detection are recognized and misfire detection inhibited. These include

1. Negative torque
2. Rough road detection
3. Cylinder shut-off (ex: for engine speed limitation, vehicle speed limitation)
4. Crankshaft oscillation

Engine cold check

This test is performed

1. if cold start conditions are verified and
2. if the intake air temperature is stable during a pre-defined period of time after start (to insure that the vehicle has not been driven from a warm location to a cold location - and vice versa - which would lead to false detection).

The cold start conditions check verifies both TAM close to Coolant temperature (TCO) or TIA close to TCO. The engine cold check criteria used is different if cold conditions is detected from TAM close to TCO or from TIA close to TCO as we have not the same confidence in those two cases.

The implausibility is detected if the difference between the ambient temperature and the air intake temperature is not within its thresholds.

However several scenarios (ex: vehicle standing in the sun/strong wind/use of an engine block heater ...) could lead to a false detection. Therefore a second check (see: " ENGINE HOT CHECK " below) may be needed.

Engine hot check

This test is performed

1. if engine warm conditions are verified (nominal values for engine coolant temperature) and
2. if the vehicle is run under defined conditions (load, engine speed, vehicle speed) for a sufficient time

Under these conditions the ambient air temperature is modeled.

TAM or TIA are defined as not plausible if

1. the difference between the ambient temperature and the modeled ambient air temperature is too large.
2. or TIA has not moved since engine start (TIA stuck detected)

The ambient temperature value is defined as plausible if modeled TAM and TAM values are similar.

Input and Output signals of the Powertrain Control Unit (PCU)

INPUT AND OUTPUT SIGNALS OF POWERTRAIN CONTROL UNIT (PCU)

Input and Output signals of the Gearbox Interface Unit (GIU)

INPUT AND OUTPUT SIGNALS OF GEARBOX INTERFACE UNIT (GIU)

OBD-II CONNECTOR

The diagnostic plug is located on the underside of the dashboard to the left of the driver and is fitted with a hinged cover, which hinges away from the driver.

This cover has the letters OBD on it and includes also an electrical function (resistance).

Scheme 230