Engine Controls - Self-Diagnostics - Without Codes Land Rover Discovery L318

VEHICLE IDENTIFICATION

VEHICLE IDENTIFICATION

INTRODUCTION

Note. For specific DTC testing, see ON-BOARD DIAGNOSTICS - DISCOVERY & RANGE ROVER article.

The Engine Control Module (ECM) controls engine fuelling using sequential injection to all cylinders. Four double-ended ignition coils provide ignition.

The ECM detects and corrects cylinder knock by advancing or retarding the ignition timing. In the event of a knock system failure a safe ignition map is used.

The ECM uses the inputs from sensors to control engine performance and restrict emissions in line with Onboard Diagnostics II (OBDII). These sensors include a Mass Air Flow (MAF) Sensor, Throttle Position (TP) Sensor, Engine Coolant Temperature (ECT) Sensor and Oxygen (O2) Sensors. The ECM also receives vehicle data, such as road speed from other control modules. The Central Processor Unit (CPU) within the ECM processes all of these inputs, applies correction factors, such as short and long term fuel trim, and issues commands to the engine actuators, injectors and coils.

On vehicles equipped with automatic transmissions the ECM is connected to the automatic Transmission Control Module (TCM) via the Controller Area Network (CAN) bus. The CAN bus conveys data, requests and messages between the control modules. Generally the automatic TCM passes OBD data and requests to the ECM, which stores freeze frame data and activates the Malfunction Indicator Lamp (MIL) when a fault occurs.

DIAGNOSTIC TROUBLE CODES & FREEZE FRAMES

The ECM and automatic TCM software monitors each fault condition and allocates a mnemonic Diagnostic Trouble Code (DTC) to specific faults; e.g. P0170 fuel trim malfunction. The software also checks that the monitoring conditions are valid and the current status of the fault. There are common condition flags for each fault module.

Generally, an emission relevant fault is not reported as soon as it occurs, but only after it is flagged during a second valid drive cycle. A drive cycle is defined by a period of engine operation equal to, or more than 10 seconds and the diagnostic fault path in question having been completed at least once. If the fault is still present on the subsequent drive cycle, the OBD system logs the fault and freeze frame data and illuminates the MIL.

If the fault is not present in the subsequent driving cycle, the system holds it as a temporary fault and counts a number of drive cycles before deleting it from the fault memory providing it does not reoccur. A re-occurring fault will be immediately logged as a permanent emissions fault, and may illuminate the MIL according to the type of fault.

When an emissions fault is recognized, the system monitors over Warm Up Cycles (WUC). A warm up cycle is defined by a period of engine operation where the ECT has increased by 21°C (40°F) and exceeds 71°C (160°F).

Monitoring during warm up is also relevant to permanent faults. If the flagged fault is not present in a subsequent drive cycle, the warm up cycle counter is started. If the fault is not flagged again, the MIL remains illuminated but is extinguished after 3 fault free WUC. The fault is finally deleted from the fault memory after 40 fault free WUC.

In the case of misfire monitoring two levels of misfire are checked

1. Emission relevant misfire is monitored over 1000 engine revolutions and 2 drive cycles.
2. Catalyst damage misfire is monitored over 200 engine revolutions. If the threshold is exceeded in any 200 engine revolutions segment the MIL is immediately flashed to signal the driver to reduce engine load. When the misfire decreases below the catalyst damage threshold or ceases altogether the MIL is permanently illuminated.

If the freeze frame memory is free the first occurring fault will store freeze frame data regardless of the source. If a subsequent fault occurs, the current freeze frame data is not overwritten unless this fault is of higher freeze frame priority. CARB faults, freeze frame data and other parameters can be read through the diagnostic port via a generic scan tool.

SYSTEM INTERFACES

The M5.2.1 ECM has some bi-directional (input and output) interfaces, and these are as follows

1. Diagnostics interface via K-Line.
2. CAN interface to the automatic TCM.

There are also interactions between the M5.2.1 ECM and other vehicle systems such as the Anti-lock Braking System (ABS) system.

Inputs

1. Ignition Switch (Position II)
2. TP Sensor
3. Immobilizer Interface
4. Engine Speed and Position Sensor (Crankshaft Sensor)
5. Camshaft Position Sensor
6. ECT Sensor
7. Intake Air Temperature (IAT) Sensor (Integrated into the MAF Sensor)
8. MAF Sensor
9. Knock Sensors (2 off)
10. O2 Sensors (4 off)
11. Fuel Tank Pressure Sensor (Except Discovery LEV Phase II and ULEV)
12. Fuel Level Sensor (Discovery Series II, NAS Tier I and LEV Phase I)
13. Self Levelling, Anti Lock Braking System (SLABS) Vehicle Speed (Discovery Series II only)
14. SLABS Rough Road signal (Discovery Series II only)
15. ABS Vehicle Speed (Range Rover 38A only)
16. ABS Rough Road signal (Range Rover 38A only)
17. Transfer Box MIL request (Range Rover 38A only)
18. Thermostat Monitoring - bottom hose temperature (LEV Phase II and ULEV only)
19. Diagnose Module - Tank Leakage (DMTL) 0.020" (0.5 mm) Leak Detection (Discovery LEV Phase II and ULEV only)
20. Analogue Fuel Level (Range Rover 38A, Discovery LEV Phase II and ULEV)
21. Air Conditioning Standby
22. Air Conditioning Request (Range Rover 38A only)

Outputs

1. MIL
2. Fuel Injectors (8 off)
3. Ignition coils (4 Double Ended)
4. O2 Sensor Heaters (4)
5. Fuel Pump Relay
6. Air Conditioning Compressor enable
7. Air Conditioning Condenser Fans Relay
8. Evaporative Emission Canister Vent Valve
9. Evaporative Emission Canister Purge Valve
10. Idle Speed Control Valve
11. Instrument Pack "ECT Signal" - Pulse Width Modulation (PWM) signal (Discovery Series II only)
12. SLABS Hill Decent Control (HDC) - Multiplexed PWM signal (Discovery Series II only)
13. Engine Speed signal
14. Environmental-Box (E-Box) Cooling Fan (Range Rover 38A only)
15. Fuel Used signal (Range Rover 38A only)
16. DMTL Pump - 0.020" (0.5 mm) (Discovery LEV Phase II and ULEV only)
17. DMTL Valve - 0.020" (0.5 mm) (Discovery LEV Phase II and ULEV only)
18. Secondary Air Injection Pump Relay (LEV Phase I, Phase II and ULEV only)
19. Secondary Air Injection Control Valve (LEV Phase I, Phase II and ULEV only)

DESCRIPTION

Mode $06 enables access to the most current diagnostic results and thresholds of non-continuous diagnostic routines. Each individual parameter is identified by a Component Identifier (CID).

Following a power fail or after a delete error memory (Mode 3) request all values will be set to $00.

Values are stored in the battery backed RAM. Additional diagnostic results are available for LEV phase I, Phase II and ULEV vehicles.

TID Services

Identifies the TID services supported by the ECM, 0 = No, 1 = Yes.

1. DATA 3 - $FF (no significance)
2. DATA 4 - TID $01 - TID $08 (Bit 7 corresponds to TID $01)
3. DATA 5 - TID $09 - TID $10
4. DATA 6 - TID $11 - TID $18
5. DATA 7 - TID $19 - TID $20 (Bit 0 corresponds to TID $20)

TIDs $20; $40; $60; $80; $A0; $C0 and $E0 respond similarly for their block of 32 TIDs.

For all supported TIDs the following applies

1. DATA 3 - Bit 0 - 6: Number of the measuring path within the TID, i.e.; the component identifier (CID). Bit 7: Type of test limit: 0 = Test Limit Is Maximum Value - The test fails if test value is greater than test limit. 1 = Test Limit Is Minimum Value - The test fails if test value is less than test limit.
2. DATA 4 + 5 - 2-byte value of the measured value.
3. DATA 6 + 7 - 2-byte value of the threshold value.

Catalyst Conversion

For additional catalyst conversion J1979 Mode $06 Data testing (Scheme 2)

1. DATA 3 (TC6KATC/2) - Bit 0 - 6: Number of the measuring path within the TID = CID. Bit 7: Type of test limit: 0 = Test Limit Is Maximum Value - Test fails if test value > test limit. 1 = Test Limit Is Minimum Value - Test fails if test value < test limit.
2. DATA 4 + 5 (TC6KATW/2) - 2-byte value of the measured value.
3. DATA 6 + 7 (TC6KATS/2) - 2-byte value of the threshold value.

Scheme 2

O2 Sensors

Not supported - covered by mode 5.

Secondary Air Injection System

Secondary Air Injection System (Supported for LEV Phase I, Phase II and ULEV). For additional secondary air injection system J1979 Mode $06 Data testing (Scheme 3)

1. DATA 3 (TC6SLS/2) - Bit 0 - 6: Number of the measuring path within the TID = CID. Bit 7: Type of test limit: 0 = Test Limit Is Maximum Value - Test fails if test value > test limit. 1 = Test Limit Is Minimum Value - Test fails if test value < test limit.
2. DATA 4 + 5 (TC6SLSW/2) - 2-byte value of the measured value.
3. DATA 6 + 7 (TC6SLSS/2) - 2-byte value of the threshold value.

Scheme 3

Exhaust Gas Recirculation

Not fitted.

EVAP System - Large Leak

Vehicles with 0.040" (1.0 mm) Leak Detection System. For additional EVAP system large leak J1979 Mode $06 Data testing (Scheme 4)

1. DATA 3 (TC6TESC) - Bit 0 - 6: Number of the measuring path within the TID = CID. Bit 7: Type of test limit: 0 = Test Limit Is Maximum Value - Test fails if test value > test limit. 1 = Test Limit Is Minimum Value - Test fails if test value < test limit.
2. DATA 4 + 5 (TC6TESW) - 2-byte value of the measured value.
3. DATA 6 + 7 (TC6TESS) - 2-byte value of the threshold value.

Scheme 4

EVAP System - Small Leak

Vehicles with 0.020" (0.5 mm) Leak Detection System. For additional EVAP system small leak J1979 Mode $06 Data testing (Scheme 5)

EVAP Canister Purge Valve

1. DATA 3 (TC6TESC) - Bit 0 - 6: Number of the measuring path within the TID = CID. Bit 7: Type of test limit: 0 = Test Limit Is Maximum Value - Test fails if test value > test limit. 1 = Test Limit Is Minimum Value - Test fails if test value < test limit.
2. DATA 4 + 5 (TC6TESW) - 2-byte value of the measured value.
3. DATA 6 + 7 (TC6TESS) - 2-byte value of the threshold value.

Scheme 5

DMTL Module

For additional DMTL module J1979 Mode $06 Data testing (Scheme 6)

1. DATA 3 (m6cddmtl) - Bit 0 - 6: Number of the measuring path within the TID = CID. Bit 7: Type of test limit: 0 = Test Limit Is Maximum Value - Test fails if test value > test limit. 1 = Test Limit Is Minimum Value - Test fails if test value < test limit. DATA 4 + 5 (m6wddmtl_w) - 2-byte value of the measured value. DATA 6 + 7 (m6sddmtl_w) - 2-byte value of the threshold value.

Scheme 6

O2 Sensor Heating

Not supported - continuous monitor.

Catalyst Heater

Not fitted.

Camshaft Shift

Not fitted.

Thermostat Diagnosis

For additional thermostat diagnosis J1979 Mode $06 Data testing (Scheme 7)

1. DATA 3 (m6cthm) - Bit 0 - 6: Number of the measuring path within the TID = CID. Bit 7: Type of test limit: 0 = Test Limit Is Maximum Value - Test fails if test value > test limit. 1 = Test Limit Is Minimum Value - Test fails if test value < test limit.
2. DATA 4 + 5 (m6wthm) - 2-byte value of the measured value.
3. DATA 6 + 7 (m6sthm) - 2-byte value of the threshold value.

PARAMETER DESCRIPTIONS

For J1979 Mode $06 Data parameter descriptions (Scheme 8), (Scheme 9) and (Scheme 10).

Scheme 7

Scheme 8

Scheme 9

Catalyst monitoring is based on the monitoring of oxygen storage capability. The engine closed loop feedback control generates Lambda (air fuel ratio) oscillations in the exhaust gas. These oscillations are damped by the oxygen storage activity of the catalyst. The amplitude of the remaining Lambda oscillations downstream of the catalyst indicates the storage capability.

In order to determine catalyst efficiency, the amplitude ratio of the signal oscillations of the upstream and downstream Lambda sensors is determined. This information is evaluated separately in different engine load and speed ranges. If there is an indication of low storage capability in a certain number of operating ranges, a defective catalyst is diagnosed.

Note. Definition of Lambda: The stoichiometric air fuel ratio is the mass ratio of 14.7 kg of air to 1 kg of gasoline theoretically necessary for complete combustion. The excess air ratio (Lambda) indicates the deviation of the actual air fuel ratio from the theoretical air fuel ratio. Thus Lambda = actual inducted air mass/theoretical air requirement.

Computation Of Amplitude Ratio

The first step is the computation of the amplitude of the signal oscillations of the oxygen sensors upstream and downstream of the catalyst. This is accomplished by extracting the oscillating signal component, computing the absolute value and averaging over time. The result of dividing the downstream amplitude value by the upstream amplitude value is called the Amplitude Ratio (AV). This AV value is the basic information necessary for catalyst monitoring. It is computed continuously over a certain engine load and speed range. The signal paths for both sensor signals are identical, so that variations, like an increase in the control frequency, affect both signal paths in the same way and are compensated for by the division.

Post Processing

The actual amplitude ratio is compared with a limit value according to the load and speed range the engine is operating in. The result of this comparison, which is the difference of the two values, is accumulated separately for each range. Thus, even short time periods of driving in a certain range yield additional information.

By using separate load and speed ranges in combination with the accumulation of information a monitoring result can be obtained during a Federal Test Procedure (FTP) cycle.

Fault Evaluation

The accumulated information about the amplitude ratio becomes more and more reliable as different load and speed ranges are used during a driving cycle. If the amplitude ratio is greater than fixed map values a fault is detected and an internal fault flag will be set. If the fault is detected again in the next driving cycle the MIL will be illuminated.

Since the monitored engine has a catalyst for each of two cylinder banks, two evaluations are made with differing fault thresholds, one test is for deterioration in one of the catalysts and the second is at a reduced threshold to check for deterioration in both catalysts.

Check Of Monitoring Conditions

The monitoring principle is based on the detection of relevant oscillations of the downstream oxygen sensor signal during regular Lambda control. It is necessary to check the driving conditions to ensure that regular lambda control is possible, e.g. fuel cut off not present. For a certain time after enabling Lambda control, the computation of the amplitude values and their post processing is halted, in order to avoid a distortion of the monitoring information. For monitoring structure (Scheme 11) For system operation (Scheme 12) For catalyst monitoring operation (Scheme 13)or (Scheme 14).

Scheme 10

Scheme 11

Scheme 12

Scheme 13

The method of engine misfire detection is based on evaluating engine speed fluctuations.

In order to detect misfiring in any cylinder, the torque of each cylinder is evaluated by recording the time between two ignition events; this is a measure of the mean value of the speed for this angular segment. Since a change in the engine torque results in a change of the engine speed. Additionally, the influence of the load torque at the wheels needs to be determined. This is to take account of the influences of different road surfaces, e.g. pavement, pot holes etc.

If the mean engine speed is measured, influences caused by road surfaces have to be eliminated.

This method consists of the following main parts

1. Data acquisition, including adaptation of the sensor wheel.
2. Calculation of engine roughness.
3. Comparison with a threshold, which depends on the operating conditions.
4. Identification of extreme conditions, during which misfire detection cannot be enabled due to a risk of falsely detecting misfire.
5. Fault processing, counting procedure of single misfire events, recording of any diagnostic trouble codes and MIL illumination.

For misfire monitoring structure, see

(Scheme 15)

Scheme 14

Data Acquisition

The duration of the crankshaft segments is measured continuously for every combustion cycle.

Crankshaft Position Sensor Wheel Adaptation

Within a defined engine speed range and during fuel cut-off, the adaptation of the crankshaft position sensor wheel tolerances is performed. As the adaptation process progresses, the sensitivity of the misfire detection is increased. The adaptation values are stored in non-volatile memory and are taken into consideration during the calculation of the engine roughness.

Misfire Detection

The following steps are performed for each measured segment, corrected by the appropriate crankshaft position sensor wheel adaptation

1. Calculation Of The Engine Roughness - The engine roughness is derived from the differences of the segment durations. Different statistical methods are used to distinguish between normal changes of the segment duration and any changes due to misfiring.
2. Detection Of Multiple Misfiring - If several cylinders are misfiring (e.g. alternating one combustion/one misfire event), the calculated engine roughness values may be so low, that the threshold is not exceeded during misfiring and, therefore, misfiring would not be detected. Based on this fact, the periodicity of the engine roughness value is used as additional information during multiple misfiring. The engine roughness value is filtered and a new multiple filter value is created. If this filter value increases due to multiple misfiring, the roughness threshold is decreased. By applying this strategy, multiple misfiring can be detected.
3. Calculation Of The Engine Roughness Threshold Value - The engine roughness threshold value consists of the base value, which is determined from a load and speed dependent map. During warm-up an ECT dependent correction value is added. For multiple misfiring the threshold is reduced by an adjustable factor. Before sufficient crankshaft position sensor wheel adaptation has occurred, the engine roughness threshold is limited to a speed dependent minimum value. A change of the threshold towards a smaller value is limited by a variation constant.

Determination Of Misfiring

Misfire detection is performed by comparing the engine roughness threshold with the engine roughness value.

Statistics, Fault Processing

Within an interval of 1000 crankshaft revolutions the detected misfire events are summed for each cylinder. (Scheme 16) If the sum of all cylinder misfire incidents exceeds a predetermined value, the preliminary diagnostic trouble code for emission relevant misfiring is stored. If only one cylinder is misfiring, a cylinder selective diagnostic trouble code is stored. If more than one cylinder is misfiring, the diagnostic trouble code for multiple misfiring is also stored. If the misfire is again detected on a subsequent drive cycle, then the MIL is illuminated and the appropriate diagnostic trouble code is stored.

Within an interval of 200 crankshaft revolutions the detected number of misfiring events is weighted and calculated for each cylinder. The weighting factor is determined by a load and speed dependent map.

If the sum of cylinder misfire incidents exceeds a predetermined value the diagnostic trouble code for indicating catalyst damage relevant misfiring is stored and the MIL is illuminated at once (flashing). (Scheme 17)or (Scheme 18).

If the cylinder selective count exceeds the predetermined threshold the following measures are instituted

1. The oxygen sensor closed loop system is switched to open loop.
2. The appropriate cylinder selective DTCs is/are stored.
3. If more than one cylinder is misfiring, the DTC for multiple misfire is also stored.

All misfire counters are reset after each interval.

Scheme 15

Scheme 16

Scheme 17

The secondary air injection system consists of an electric pump that is controlled by the ECM via a relay. Air is supplied by the pump to two vacuum operated control valves, one per cylinder bank. From each of the control valves air is delivered to the exhaust ports of the center two cylinders of each cylinder bank. The vacuum signal is switched via an ECM controlled solenoid valve. A vacuum reservoir ensures that there is always sufficient depression to operate the control valves.

Diagnosis of the secondary air injection system can take place in two steps. There is a passive diagnostic which checks for a lean shift in the signals from the front oxygen sensors during secondary air injection operation and there is an active check, which only runs if the passive check fails to achieve sufficient test results in any drive cycle. The active test has two parts; firstly the secondary air injection pump will be run with the control valves shut. If the valves are leaking or stuck open, the feedback fuelling will shift lean and a fault will be detected. If the valve check is passed, then the valves will be opened and if sufficient secondary airflow exists, then the fuelling will be shifted lean. If the lean shift is less than the required threshold, then a fault is stored.

Additionally, a total absence of secondary injection airflow does not cause the vehicle to exceed the appropriate monitoring threshold. Therefore the system only requires a functional check for the presence of secondary air.

Passive Secondary Air Injection Diagnostic

For this test to run the front O2 sensors must have been ready for operation for longer than a certain time, the secondary air injection system must be operating, the engine speed and load must be within a pre-determined window, engine airflow must be less than an altitude dependent threshold and the ECT must be greater than a threshold. (Scheme 19)

The front O2 sensors are monitored over a time period and the minimum voltage value recorded. When a second timer expires, a test counter is incremented and the minimum sensor value is compared with a threshold. If the voltage is less than the threshold then a counter of good test results is incremented. When the test counter reaches a threshold, the number of good test results is compared with a limit value. If the number of good results is greater than the limit then the Secondary Air Injection system is functioning correctly, otherwise a fault is stored and the MIL is illuminated on the next drive cycle, if the fault is again present. (Scheme 21)

Scheme 18

Active Secondary Air Injection Diagnostic

If on any drive cycle during which secondary air injection operation has occurred, there are insufficient passive diagnostic test results for fault determination. The system will then attempt to perform an active check of the secondary air injection system. For an active test to occur, the vehicle must be at rest with the engine idling, feedback fuel control enabled, below an altitude threshold, with the engine having been running for longer than a pre-determined time and secondary air injection not operating. If the EVAP canister purge is operating, then it will be ramped down to zero.

The active test is in two parts. (Scheme 20) First the current feedback correction factor is recorded and the secondary air injection pump turned on, but with the control valves shut. If the fuelling enriches by more than a threshold, then the valves are leaking or stuck open, but if after a timer has elapsed the feedback correction is below the threshold, then the system proceeds with a flow check.

For the second part of the active diagnostic the valves are opened and if after a time limit, the feedback has not enriched the fuelling by more than a second threshold, then a problem exists with the system and if it is present again on a subsequent drive cycle, a fault is stored and the MIL illuminated. (Scheme 21)

Scheme 19

Scheme 20

The evaporative emission system monitoring permits the detection of leaks in the fuel evaporative emission control system with a diameter of 0.040" (1.0 mm) or larger. (Scheme 23)

For this purpose, a system pressure check is performed at idle with the vehicle stationary. Since vapor generation in the fuel tank could cause the false detection of a system leak, the first step is to close the EVAP canister purge valve and EVAP canister vent solenoid valve. Any pressure build-up is then measured, so that later results can be compensated for this fuel evaporation effect.

The EVAP canister purge valve is opened and the EVAP canister vent solenoid valve is closed. With this procedure a vacuum in the tank is created, which is measured by the fuel tank pressure sensor.

If no vacuum is detected, a large leak is assumed and the diagnosis is halted. If a large lean correction of the oxygen sensor controller is detected during the vacuum build-up, then the check is also halted, since fuel vapor is present in the system due to a high EVAP canister loading and idle instability will occur if the test is continued.

At a pre-determined vacuum the EVAP canister purge valve is closed, and the system is now considered CLOSED. From the gradient of the vacuum decay and the previously measured fuel vapor generation pressure rise, the presence of a leak can be inferred. The decay of the vacuum gradient also depends on the fuel level in the tank. The fuel level is roughly derived from the gradients of the vacuum build-up and vacuum decay and this information is also used when determining if a leak is present.

EVAP System Monitoring Structure

Typical fuel tank pressure characteristic during the diagnostic test. (Scheme 22) For evaporative emission system monitoring with 0.040" (1.0 mm) diameter leak (Scheme 24)and (Scheme 25).

Scheme 21

Scheme 22

Scheme 23

Scheme 24

The evaporative emission monitoring system used for the Discovery 2001MY onwards permits the detection of leaks with a diameter of 0.020" (0.5 mm) or greater. This is achieved by means of a pressure test of the system. (Scheme 28), (Scheme 29) and (Scheme 30). This is performed by the DMTL, which is an electrically operated pump fitted to the atmospheric air intake of the EVAP Canister. From the 2002MY this unit contains an electric heater to prevent condensate formation.

The test proceeds in 2 stages

1. Reference Leak Measurement - The pump operates against the reference restriction within the DMTL. The ECM measures the current consumption of the pump motor during this phase.
2. Leak Measurement - The solenoid in the DMTL is operated in order to shut off normal purge airflow into the EVAP Canister. (Scheme 26) The pump can now pressurize the fuel tank and vapor handling system. The ECM again measures the current consumed by the pump motor and by comparing this with the reference current, determines if a leak is present or not. (Scheme 27) A high current indicates tight system and a low current indicates a leaking system.

For evaporative emission system monitoring with 0.020" (0.5 mm) diameter leak (Scheme 31), (Scheme 32) and (Scheme 33).

Scheme 25

Scheme 26

Scheme 27

Scheme 28

Scheme 29

Scheme 30

Scheme 31

Scheme 32

Primary Mixture Control

The air mass taken in by the engine and the engine speed are measured. These signals are used to calculate an injection signal. This primary mixture control follows fast load and speed changes.

Lambda-Control

The ECM compares the oxygen sensor signal upstream of the catalyst with a reference value and calculates a correction factor for the primary control. (Scheme 34)

Scheme 33

Adaptive Control

Drifts and faults in the sensors and actuators of the fuel delivery system, as well as unmetered air leakage into the intake system influence the primary control. This causes deviations in the air to fuel ratio. The adaptive control determines the controller correction in two different ranges. (Scheme 35)

Scheme 34

Lambda deviations in Range 1 are compensated by an additive correction value multiplied by an engine speed term. By this means an additive correction per time unit is derived.

Lambda deviations in Range 2 are compensated by a multiplicative factor.

Each value is determined only within its corresponding range. But each adaptive value corrects the primary control within the whole load and speed range of the engine. After the next start, the stored adaptive values are included in the calculation of the primary fuel control; just before closed-loop fuelling control is activated.

Fuel Delivery System Abbreviations

Abbreviations for the fuel delivery system

1. QU1 - Upper Airflow Threshold Range 1
2. NU1 - Upper Engine Speed Threshold Range 1
3. tra - Additive Learning Correction Coefficient Per Time Unit (Range 1)
4. TRADN - Lower Diagnosis Threshold Of tra
5. TRADX - Upper Diagnosis Threshold Of tra
6. TLARN - Upper Engine Load Threshold f (n), Range 2
7. QL2 - Lower Airflow Threshold Range 2
8. TLL2 - Lower Engine Load Threshold Range 2
9. fra - Multiplicative Learning Correction Coefficient (Range 2)
10. FRADN - Lower Diagnosis Threshold Of fra
11. FRADX - Upper Diagnosis Threshold Of fra

Diagnosis of Fuel Delivery System

Faults in the fuel delivery system can occur which cannot be compensated for by the adaptive control. In this case the adaptive values leave a predetermined range. If the adaptive value is outside this predetermined range, and then if the condition is again present on a subsequent drive cycle, the MIL is illuminated and the appropriate diagnostic trouble codes are stored.

Fuel System Monitoring Structure

For fuel system monitoring structure and DTC testing (Scheme 36)and (Scheme 37).

Scheme 35

Scheme 36

The response rates of the upstream O2 sensors are monitored by measuring the period of the Lambda control oscillations. This period monitoring allows the detection of a slow O2 sensor. (Scheme 38)and (Scheme 39).

Scheme 37

Scheme 38

Oxygen Sensor Heater Monitoring Description

For proper functioning of an oxygen sensor, its element must be heated. A non-functioning heater delays the oxygen sensor's readiness for closed loop control and influences emissions.

The monitoring function measures both oxygen sensor heater current (voltage drop over a shunt) and the heater voltage (heater supply voltage), so that the oxygen sensor heater resistance can be calculated. If the oxygen sensor heater resistance is exceeds a minimum or maximum threshold an oxygen sensor heater fault is detected.

The monitoring function is activated once per drive cycle, as long as the heater has been switched on for a certain time period and the current has stabilized.

Characteristics

1. ECM controlled switching of the oxygen sensor heater.
2. One shunt for each pair of oxygen sensors upstream and downstream of the catalysts for current measurement.

Oxygen Sensor Heater Monitoring Structure

For oxygen sensor heater monitoring structure (Scheme 40)

The oxygen sensor heater resistance is calculated from the following equation. (Scheme 41)

Scheme 39

Scheme 40

Oxygen Sensor Circuit Monitoring

Monitoring for electrical faults in the oxygen sensors both upstream and downstream of the catalyst. For Discovery (Scheme 42), (Scheme 43) and (Scheme 44). For Range Rover (Scheme 45), (Scheme 46) and (Scheme 47).

Implausible voltages

1. Analogue to Digital Converter (ADC) voltages exceeding the maximum threshold VMAX are caused by a short circuit to battery positive.
2. ADC voltages falling below the minimum threshold VMIN are caused by a short circuit of the oxygen sensor signal or oxygen sensor ground to the ECM ground.
3. An open circuit of the oxygen sensor can be detected if the ADC voltage remains within a specified range after the oxygen sensor has been heated for a certain time.

Scheme 41

Scheme 42

Scheme 43

Scheme 44

Scheme 45

Scheme 46

The diagnostic checks for a partially open thermostat, under conditions when the thermostat would be expected to be shut. (Scheme 48)

A second ECT sensor is installed in the outlet from the radiator. If the enablement criteria are met and the ECT is less than the normal thermostat opening temperature the diagnostic will run. (Scheme 49)

The diagnostic compares the difference between ECT and the radiator outlet temperature. This gives the temperature drop across the radiator. (Scheme 50)and (Scheme 51).

If the temperature drop is less than a threshold, and there is flow across the radiator, this is caused by leakage through the thermostat.

Scheme 47

Scheme 48

Scheme 49

Scheme 50

This sensor is the most important sensor on the vehicle, without it the engine cannot run. There is no backup strategy or limp home facility should it fail. The sensor produces the signal which enables the ECM to determine the angle of the crankshaft, and the engine RPM. From this, the point of ignition, fuel injection, etc. is calculated. If the signal wires are reversed, a 3° advance in timing will occur, as the electronics within the ECM uses the falling edge of the signal waveform as its reference/timing point for each tooth.

The reluctor is machined and has a tooth pattern based on 60 teeth at 6 degrees intervals and 3 degrees wide: two of the teeth are removed to provide a hardware reference mark which is 60 degrees before top dead center No. 1 cylinder. (Scheme 52)

Scheme 51

The sensor operates by generating an output voltage caused by the change in magnetic field, which occurs as the teeth pass in front of the sensor. The output voltage varies with the speed of the teeth passing the sensor; the higher the engine speed, the higher the output voltage. Note that the output is also dependent on the air gap between the sensor and the teeth (the larger the gap, the weaker the signal, the lower the output voltage).

There are two diagnostic checks on the output signal of this sensor

1. The hardware reference mark created by the missing teeth is outside the search window and the engine speed is greater than 500 RPM.
2. The hardware reference mark is outside the search window by more than one tooth and the engine speed is greater than 500 RPM.

The ECM transmits the engine speed to the automatic TCM using CAN, while all other control modules are hardwired. (Scheme 53)

Scheme 52

This is a Hall effect sensor producing four pulses for every two engine revolutions. The sensing element is positioned between 0.0-2.0 mm (0.0-0.079") from the side of the cam gear wheel. The sensor is, in effect, a magnetically operated electrical switch, switching a battery supply level voltage on or off dependent on the position of the cam gear wheel with respect to the sensor. (Scheme 54)

Scheme 53

The cam gear wheel has four slots machined in it enabling cylinder identification every 90°. The signal is used for cylinder recognition; enabling sequential fuel injection, knock control and cylinder identification for diagnostic purposes.

The system checks the camshaft position sensor signal at every software reference mark i.e., 54° before top dead center (2 teeth after the reluctor 2nd missing tooth). A fault condition is recognized if the signal does not change state (high to low or low to high voltage) every crankshaft revolution. (Scheme 55)

Scheme 54

This sensor is a temperature dependent resistor (thermistor), which is a Negative Temperature Co-efficient (NTC) type, i.e. resistance decreases with increasing temperature. The sensor forms part of a voltage divider chain with a pull up resistor within the ECM. The change in resistance relates to change in the ECT.

The sensor is vital to the correct running of the engine as a richer mixture is required at lower block temperatures for good quality starts and smooth running, leaning off as the temperature rises to maintain emissions and performance. Should the sensor fail there is a software ECT warm-up model which will supply a changing default value during the warm up stage of the engine, based upon IAT. After the software model reaches 60°C (140°F) ECT, a fixed default value of 85°C (185°F) is used. The model also forms part of the diagnostics for the ECT sensor, in conjunction with open and short circuit tests. (Scheme 56)

A fault condition is recognized if the ECM is powered up and the ECT sensor resistance exceeds a minimum or maximum threshold, or the difference between the ECT model and the temperature indicated by the ECT sensor is greater than a threshold.

Scheme 55

MASS AIRFLOW SENSOR & INTAKE AIR TEMPERATURE SENSOR

Note. The MAF sensor is a combined Mass Airflow (MAF) sensor and Intake Air Temperature (IAT) sensor.

Airflow is determined by the cooling effect of the intake air passing over a "hot film" element contained within the device. The higher the air flow the greater the cooling effect and the lower the electrical resistance of the "hot film" element. The signal from the device is then used by the ECM to calculate the Mass Airflow (MAF) into the engine.

The measured airflow is used in determining the fuel quantity to be injected in order to maintain the stoichiometric air fuel ratio required for correct operation of the engine and exhaust catalysts. Should the device fail there is a software backup strategy that will be evoked once a fault has been diagnosed. A fault is detected if the MAF signal exceeds the maximum or minimum threshold for a given speed range or the difference between the calculated load and the actual MAF signal is too great. (Scheme 57)

Scheme 56

The Intake Air Temperature (IAT) sensor is a temperature dependent resistor (thermistor), i.e. the resistance of the sensor varies with temperature. The thermistor is an NTC type element, which means that the sensor resistance decreases as the sensor temperature increases. The sensor forms part of a voltage divider chain with an additional resistor in the ECM. The voltage from this network changes as the sensor resistance changes, relating the IAT to the voltage measured by the ECM.

A fault is detected if the resistance of the sensor exceeds a minimum or maximum threshold. (Scheme 58)

Scheme 57

The ECM uses active knock control, which serves to prevent engine damaging pre-ignition or detonation under all operating conditions enabling the engine to operate without additional safety margins. For the ECM to be able to determine the point at which a cylinder is pre-detonating, 2 piezo ceramic sensors are mounted on the engine block. Each sensor monitors all 4 cylinders in a bank (i.e. cylinders 1, 3, 5 & 7, and cylinders 2, 4, 6 and 8) by converting the engine block noise into a suitable electrical signal, which is then transmitted back to the ECM via a shielded cable. The signal is then processed within the ECM to identify the data that characterizes knocking. For knock sensor testing (Scheme 59)

There are three knock sensor diagnostic checks during which a fault is detected if

1. The sensor signal is less than the minimum engine RPM dependent threshold.
2. The sensor signal is greater than the maximum engine RPM dependent threshold.
3. The error counter for the verification of knock internal circuitry is exceeded.

Scheme 58

The sensor is a variable resistor, which is used to determine the position of the throttle plate and the rate of change in its angle. A software strategy within the ECM enables the closed throttle position to be learned, enabling the sensor to be fitted without the need for adjustment. The signal is used by the ECM as part of the transient fuelling strategy and to determine the closed throttle position for idle speed control, in conjunction with road speed.

The signal is not only checked for range (exceeds a minimum or maximum threshold), but also for plausibility against MAF. If the load-monitoring fault is stored, it is indicative of a blocked air filter or collapsed air intake duct etc. It is also probable that the altitude adaptation factor is incorrect under these conditions. For throttle position sensor testing (Scheme 60)

Scheme 59

The ECM performs a number of self-test integrity diagnostics on its internal hardware and software to check for faults. An error is detected if the ECM receives no CAN messages for at least 0.8 seconds, the calculated checksums at power down do not match the values stored in flash Electrically Erasable Programmable Read Only Memory (EEPROM) or the internal or external RAM fails a read/write test. For engine control module self test testing (Scheme 61)

Scheme 60

This input is required as part of the misfire detection system in order to record if a LOW FUEL situation was present when misfire was detected and logged as a fault. On Range Rover 38A the ECM is required to read an analogue fuel level input and determine the LOW FUEL condition from this signal. Discovery Series II had an active high digital input until 2000MY, at which point this input also became an analogue signal. For fuel level sensor testing (Scheme 62)

There are three fuel level input diagnostic checks, during which a fault is detected if

1. The input signal is less than a minimum voltage threshold.
2. The input signal is greater than a maximum voltage threshold.
3. The percentage difference between the fuel consumption calculated by the ECM and the change in the fuel tank level is greater than a threshold.

Scheme 61

The vehicle speed signal is transmitted from either the Self Levelling, Anti-lock Braking System (SLABS) or the ABS control module. This signal is then passed by the ECM to the automatic TCM via the CAN bus. The ECM has input diagnostics for this signal; the SLABS/ABS signal is compared to the vehicle speed signal on CAN from the automatic TCM, derived from the main gearbox output shaft speed; if the difference is greater than a threshold then a fault is detected. (Scheme 63)

Scheme 62

The ECM requires a permanent battery level voltage supply and a switched battery level voltage supply. The switched voltage supply is controlled by the ECM via a relay based on the condition of the ignition switch input (key position 2). At "key off" the ECM will maintain the switched supply active until various internal self-checks have been completed. (Scheme 64)

There are three battery voltage plausibility checks during which a fault is detected if

1. The battery voltage supply is less than a minimum voltage threshold.
2. The battery voltage supply is greater than a maximum voltage threshold and a jump-start condition has not been detected.
3. The battery voltage supply is less than a voltage threshold 60 seconds after the engine has been started.

Scheme 63

The SLABS/ABS control module transmits a PWM signal indicating rough road for misfire detection disablement. The ECM has input diagnostics for this signal. (Scheme 65)

There are three plausibility checks of the PWM signal during which a fault is detected if

1. The PWM signal is greater than a threshold indicating an electrical short to battery positive.
2. The PWM signal is less than a threshold indicating an electrical short to ground.
3. The PWM signal is greater than 44.92% but less than 55.08% indicating an error with the SLABS/ABS control module.

Scheme 64

This input indicates to the ECM that there is an OBD relevant error within the transfer box control module. The ECM will illuminate the MIL and store the P1701 DTC whenever this signal is true. The ECM carries out an integrity check on this signal following an IGNITION ON condition as shown below. (Scheme 66) The ECM detects a fault if any of the following conditions are satisfied

1. The line voltage is high during the low test.
2. The line voltage is low during the high test.
3. The line voltage is in an undefined state, neither high nor low.

For transfer box MIL request DTC testing, see

(Scheme 67)

Scheme 65

Scheme 66

The air conditioning system comprises of the Heating and Ventilation Control (Air Conditioning) Module (HeVAC), the air conditioning compressor and the condenser fans. The ECM controls the compressor clutch via a relay.

The control strategy of the relay features hysteresis to avoid the compressor clutch cycling while the engine is running. When there is a need for the compressor to be activated, the HeVAC module sends a request signal to the ECM, which in turn activates the compressor clutch relay. The condenser fan relay is controlled separately by both the ECM and the HeVAC module, and again, the control strategy features hysteresis to avoid the cooling fans cycling while the engine is running and the engine coolant and/or condenser temperatures fluctuate around a given threshold. When there is a need for condenser cooling for air conditioning performance the HeVAC module sends a request signal to the condenser fan relay. If there is a requirement for condenser cooling due to ECT, the ECM will send the request signal to the condenser fan relay.

When the HeVAC module requests air conditioning, the signal it sends to the ECM is through two binary switches, which sense the minimum and maximum refrigerant pressure and an evaporator thermostat. If the pressure or the temperature is below or above certain levels the binary switches will be open circuit and effectively disable the A/C request line to the ECM, which in turn will disengage the compressor clutch.

The air conditioning system is in standby mode if the HeVAC module is on and economy mode is not selected.

There are four diagnostic checks of the air conditioning system during which a fault is detected if

1. The A/C compressor clutch relay short circuit to battery positive, i.e. the driver voltage is greater than half the battery voltage when the driver is on.
2. The A/C compressor clutch relay short circuit to ground, i.e. the driver voltage is less than one third of the battery voltage when the driver is off.
3. The A/C compressor clutch relay is open circuit, i.e. the driver voltage is greater than one third of the battery voltage but less than two thirds of the battery voltage when the driver is off.
4. A/C has been requested when the system is not in standby mode, i.e. a signal rationality check.

For air conditioning system testing, see

(Scheme 68)

Scheme 67

The engine is fitted with 8 fuel injectors (one per cylinder), each of which is directly driven by the ECM. The Injectors are fed from a common fuel rail as part of a return less fuel system, with the fuel rail pressure constant at 3.5 bar (52 psi). The Fuel Pressure Regulator is integral to the fuel pump module, within the fuel tank. There is no reference signal line to the intake manifold.

The ECM monitors the output power stages of the injector drivers for electrical faults. A fault is detected if any of the following conditions is satisfied

1. Fuel injector driver short circuit to battery positive, i.e. the driver voltage is greater than half the battery voltage when the driver is on.
2. Fuel injector driver short circuit to ground, i.e. the driver voltage is less than one third of the battery voltage when the driver is off.
3. Fuel injector driver open circuit, i.e. the driver voltage is greater than one third of the battery voltage but less than two thirds of the battery voltage when the driver is off.

For fuel injectors testing, see

(Scheme 69)

Scheme 68

The load on an idling engine is a combination of both internal and external engine loads such as engine friction, water pump, air conditioning etc., which all change with time and operating conditions. The idle speed control actuator is required to enable closed loop idle speed control to compensate for these changing conditions, by regulating the airflow into the engine.

The device consists of two coils which use opposing PWM signals to control the position of opening/closing of the rotary valve. If one circuit fails the other is switched off by the ECM as soon as it recognizes the fault. This prevents the valve going to a maximum or minimum setting. There is a default position, which is determined by a permanent magnet. In the default condition the idle speed is raised and remains fixed at approximately 1200 RPM with no load.

There are eight idle speed control actuator diagnostic checks

1. Opening winding driver short circuit to battery positive, i.e. the driver voltage is greater than half the battery voltage when the driver is on.
2. Opening winding driver short circuit to ground, i.e. the driver voltage is less than one third of the battery voltage when the driver is off.
3. Opening winding driver open circuit, i.e. the driver voltage is greater than one third of the battery voltage but less than two thirds of the battery voltage when the driver is off.
4. Closing winding driver short circuit to battery positive, i.e. the driver voltage is greater than half the battery voltage when the driver is on.
5. Closing winding driver short circuit to ground, i.e. the driver voltage is less than one third of the battery voltage when the driver is off.
6. Closing winding driver open circuit, i.e. the driver voltage is greater than one third of the battery voltage but less than two thirds of the battery voltage when the driver is off.
7. Blocked Idle Air Control (IAC) valve - RPM error low, i.e. the engine speed is 100 RPM less than the target speed.
8. Blocked IAC valve - RPM error high, i.e. the engine speed is 180 RPM greater than the target speed.

For idle air control valve testing, see

(Scheme 70)

Scheme 69

The Land Rover V8 engine has a returnless fuel system. The fuel pressure regulator and filter are fitted to the IN TANK FUEL PUMP MODULE. The system pressure is maintained at a constant 3.5 bar (52 Psi), with no reference to intake manifold pressure. The ECM compensates for the non-constant pressure drop across the injector nozzles.

The fuel is supplied to the injectors from a fuel pump fitted within the fuel tank. The electrical supply to this fuel pump is controlled by the ECM via a relay and an Inertia fuel shutoff switch, which will turn off the fuel supply upon vehicle impact. The fuel system is pressurized to 3.5 bar (52 Psi) as soon as the ECM is powered up, the pump is then switched off until engine start has been achieved. If the pump runs but the fuel pressure is out of limits, adaptive fuel faults are stored. (Scheme 71)

The ECM monitors the output power stage of the fuel pump relay drive for electrical faults. A fault is detected if any of the following conditions is satisfied

1. Fuel pump relay driver short circuit to battery positive, i.e. the driver voltage is greater than half the battery voltage when the driver is on.
2. Fuel pump relay driver short circuit to ground, i.e. the driver voltage is less than one third of the battery voltage when the driver is off.
3. Fuel pump relay driver open circuit, i.e. the driver voltage is greater than one third of the battery voltage but less than two thirds of the battery voltage when the driver is off.

Scheme 70

The OBD system interfaces with the driver via the MIL, which is located in the instrument pack. A bulb check takes place every time the ignition is switched to ignition position II and until the engine is cranked.

The ECM monitors the driver junction temperature to detect an electrical fault. (Scheme 72) A fault is detected if the following condition is satisfied

1. MIL driver short circuit to battery positive, i.e. the driver stage junction temperature exceeds a temperature threshold.

Scheme 71

Hill Descent Control (HDC) operates in conjunction with the anti-lock braking system to provide greater control in off-road situations if necessary. HDC can be selected with the vehicle in any gear, but will only operate when low range gears are engaged with the vehicle traveling at less than 31 mph. During a descent, if engine braking is insufficient to control the vehicle speed, HDC (if selected) automatically operates the brakes to slow the vehicle and maintain a speed relative to the selected gear and the accelerator pedal position.

The ECM transmits throttle angle, engine torque, engine identification (V8 Thor) and transmission type to the SLABS control module to support the HDC system. This information is transmitted via a multiplexed PWM waveform.

The ECM has power stage diagnostics for the signal. (Scheme 73) A fault is detected if any of the following conditions is satisfied

1. HDC link to the SLABS control module short circuit to battery positive, i.e. the driver voltage is greater than half the battery voltage when the driver is on.
2. HDC link to the SLABS control module short circuit to ground, i.e. the driver voltage is less than one third of the battery voltage when the driver is off.
3. HDC link to the SLABS control module open circuit, i.e. the driver voltage is greater than one third of the battery voltage but less than two thirds of the battery voltage when the driver is off.

Scheme 72

The engine speed signal is sent by the ECM to the instrument pack, Body Control Module (BCM) and SLABS/ABS control module via a direct hardwired connection.

The ECM has power stage diagnostics for this signal. (Scheme 74) A fault is detected if any of the following conditions is satisfied

1. Engine speed signal driver short circuit to battery positive, i.e. the driver voltage is greater than half the battery voltage when the driver is on.
2. Engine speed signal driver short circuit to ground, i.e. the driver voltage is less than one third of the battery voltage when the driver is off.
3. Engine speed signal driver open circuit, i.e. the driver voltage is greater than one third of the battery voltage but less than two thirds of the battery voltage when the driver is off.

Scheme 73

This function is required to control the Environmental-Box (E-Box) mounted cooling fan. This fan provides cabin air into the E-Box to provide a cool temperature environment for the ECM fitted in the under-bonnet mounted E-Box. The temperature is determined by an internally (to the ECM) mounted temperature sensor. The fan will be switched on at 40°C +/- 15°C (104°F +/- 27°F) and also tested for 2 seconds every engine start.

The ECM has power stage diagnostics for this signal. (Scheme 75) A fault is detected if any of the following conditions is satisfied

1. E-Box cooling fan driver short circuit to battery positive, i.e. the driver voltage is greater than half the battery voltage when the driver is on.
2. E-Box cooling fan driver short circuit to ground, i.e. the driver voltage is less than one third of the battery voltage when the driver is off.
3. E-box cooling fan driver open circuit, i.e. the driver voltage is greater than one third of the battery voltage but less than two thirds of the battery voltage when the driver is off.

Scheme 74

The transmission range switch information and calculated range data are transmitted from the automatic TCM via the CAN bus.

The ECM performs a rationality test between these signals. (Scheme 76) A fault is detected if one the following conditions are satisfied

1. The transmission range switch information indicates low range and the calculated range information indicates high.
2. The transmission range switch information indicates high range and the calculated range information indicates low.

Scheme 75

The CAN is a high-speed serial interface for sharing dynamic signals between control modules. CAN communications are SELF CHECKED for errors, if an error is detected the message is ignored by the receiving control module. Due to the high rate of information exchange (500K baud) the system has a high degree of latency. This allows for a high amount of errors to be present without reducing the data transfer rate.

The CAN communication system is a differential bus using a twisted pair, which is normally very reliable. If either or both of the wires of the twisted pair CAN bus is open or short-circuited a CAN time out fault will occur and the automatic TCM defaults to third gear. In order to alert the driver the SPORT and MANUAL warning lights in the instrument pack will flash alternatively.

An error is detected if the ECM receives no CAN messages for at least 0.8 seconds or the duration of the automatic TCM retard request is greater than 10 seconds. (Scheme 77)

Scheme 76

A spiral oil separator is located in the stub pipe to the ventilation hose on the right hand cylinder head rocker cover, where oil is separated and returned to the cylinder head. The rubber ventilation hose from the right hand rocker cover is routed to a port on the right hand side of the inlet manifold plenum chamber where the returned gases mix with the fresh intake air passing through the throttle butterfly valve. see scheme 77 This pipe is primarily for part-load breathing and is connected to the engine via a restrictor that prevents an excessive vacuum building up in the crankcase at small throttle openings.

The stub pipe on the left hand rocker cover does not contain an oil separator or a restrictor and the ventilation hose is routed to the throttle body housing at the air inlet side of the butterfly valve. This pipe is for breathing at higher loads. Flow through this second pipe is negligible under normal driving conditions.

The ventilation hoses are attached to the stub pipes by metal band clamps.

Disconnection of the part-load breather is likely to result in a tendency of the engine to stall when returning to idle and the quantity of unmetered air, which flows into the intake manifold, will result in the detection of a fuel system fault by the OBD system.

For this reason, there are no separate monitors for compliance with the requirements of Positive Crankshaft Ventilation (PCV) monitoring.

Scheme 77

DRIVE CYCLES

The following are the Textbook/T4 drive cycles.

Drive Cycle A

1. Switch on the ignition for 30 seconds.
2. Ensure engine coolant temperature is less than 60°C (140°F).
3. Start the engine and allow to idle for 2 minutes.
4. Connect TestBook/T4 and check for fault codes.

Drive Cycle B

1. Switch ignition on for 30 seconds.
2. Ensure engine coolant temperature is less than 60°C (140°F).
3. Start the engine and allow to idle for 2 minutes.
4. Perform 2 light accelerations (0 to 35 mph (0 to 60 km/h) with light pedal pressure).
5. Perform 2 medium accelerations (0 to 45 mph (0 to 70 km/h) with moderate pedal pressure).
6. Perform 2 hard accelerations (0 to 55 mph (0 to 90 km/h) with heavy pedal pressure).
7. Allow engine to idle for 2 minutes.
8. Connect TestBook/T4 and with the engine still running, check for fault codes.

Drive Cycle C

1. Switch ignition on for 30 seconds.
2. Ensure engine coolant temperature is less than 60°C (140°F).
3. Start the engine and allow to idle for 2 minutes.
4. Perform 2 light accelerations (0 to 35 mph (0 to 60 km/h) with light pedal pressure).
5. Perform 2 medium accelerations (0 to 45 mph (0 to 70 km/h) with moderate pedal pressure).
6. Perform 2 hard accelerations (0 to 55 mph (0 to 90 km/h) with heavy pedal pressure).
7. Cruise at 60 mph (100 km/h) for 8 minutes.
8. Cruise at 50 mph (80 km/h) for 3 minutes.
9. Allow engine to idle for 3 minutes.
10. Connect TestBook/T4 and with the engine still running, check for fault codes.

Note. The following areas have an associated readiness test which must be flagged as complete, before a problem resolution can be verified: Catalytic converter fault. Evaporative loss system fault. HO2 sensor fault. HO2 sensor heater fault.

When carrying out a Drive Cycle C to determine a fault in any of the above areas, select the readiness test icon to verify that the test has been flagged as complete.

Drive Cycle D

1. Switch ignition on for 30 seconds.
2. Ensure engine coolant temperature is less than 35°C (95°F).
3. Start the engine and allow to idle for 2 minutes.
4. Perform 2 light accelerations (0 to 35 mph (0 to 60 km/h) with light pedal pressure).
5. Perform 2 medium accelerations (0 to 45 mph (0 to 70 km/h) with moderate pedal pressure).
6. Perform 2 hard accelerations (0 to 55 mph (0 to 90 km/h) with heavy pedal pressure).
7. Cruise at 60 mph (100 km/h) for 5 minutes.
8. Cruise at 50 mph (80 km/h) for 5 minutes.
9. Cruise at 35 mph (60 km/h) for 5 minutes.
10. Allow engine to idle for 2 minutes.
11. Connect TestBook/T4 and check for fault codes.

Drive Cycle E

1. Ensure fuel tank is at least a quarter full.
2. Carry out Drive Cycle A.
3. Switch off ignition.
4. Leave vehicle undisturbed for 20 minutes.
5. Switch on ignition.
6. Connect TestBook/T4 and check for fault codes.

See also:
• ON-BOARD DIAGNOSTICS - DISCOVERY & RANGE ROVER