Engine Controls - Self-Diagnostics - Without Codes: Other Land Rover Discovery II

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)

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 83)

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 83

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 84)

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 84

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 85)

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 85

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 86)

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 86

DMTL Module

For additional DMTL module J1979 Mode $06 Data testing (Scheme 87)

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 87

O2 Sensor Heating

Not supported - continuous monitor.

Catalyst Heater

Not fitted.

Camshaft Shift

Not fitted.

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 89) For system operation (Scheme 90) For catalyst monitoring operation (Scheme 91)or see scheme 13.

Scheme 88

Scheme 89

Scheme 90

Scheme 91

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 93) 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 94)or see scheme 17.

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 92

Scheme 93

Scheme 94

EVAP System Monitoring Structure

Typical fuel tank pressure characteristic during the diagnostic test. (Scheme 96) For evaporative emission system monitoring with 0.040" (1.0 mm) diameter leak (Scheme 98)and see scheme 24.

Scheme 95

Scheme 96

Scheme 97

Scheme 98

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 100)

Scheme 99

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 101)

Scheme 100

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 System Monitoring Structure

For fuel system monitoring structure and DTC testing (Scheme 102)and see scheme 36.

Scheme 101

Scheme 102

Oxygen Sensor Heater Monitoring Structure

For oxygen sensor heater monitoring structure (Scheme 104)

The oxygen sensor heater resistance is calculated from the following equation. (Scheme 105)

Scheme 103

Scheme 104

Oxygen Sensor Circuit Monitoring

Monitoring for electrical faults in the oxygen sensors both upstream and downstream of the catalyst. For Discovery (Scheme 106), (Scheme 107) and (Scheme 108). For Range Rover (Scheme 109), (Scheme 110) and see scheme 46.

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 105

Scheme 106

Scheme 107

Scheme 108

Scheme 109

Scheme 110

MASS AIRFLOW SENSOR & INTAKE AIR TEMPERATURE SENSOR

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

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.