A few sensor specs...
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TReK
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From: Ketchikan, Alaska, USA
A few sensor specs...
THROTTLE POSITION SENSOR
The Throttle Position Sensor (TPS ) is a potentiometer mounted at the throttle butterfly converts throttle position into an electrical signal used by the ECM (along with data from the Mass Air Flow Sensor) to determine the volume of air entering the intake manifold.
GEMS throttle circuitry is adaptable within a range of 80 to 500 mV . Within this range, the PCM will adapt to the initial setting and use it as a reference. There is no need to adjust the TPS following installation on these models. If the TPS should fail, the ECM will use a default value of 576 mV and the MIL will be illuminated.
A diagnostic trouble code is set when sensor output is less than 78 mV for longer than 160 milliseconds .
Acceleration Enhancement
The ECM increases the amount of fuel normally provided for a given throttle position during periods of peak acceleration. This allows the system to anticipate fuel needs.
Deceleration Fuel Shut-off
During throttle closed deceleration, the ECM does not activate fuel injectors (zero pulse-width) to prevent unneeded fuel from entering the cylinders. This strategy protects against catalytic converter overheating and reduces fuel consumption.
The Throttle Position Sensor (TPS ) is a potentiometer mounted at the throttle butterfly converts throttle position into an electrical signal used by the ECM (along with data from the Mass Air Flow Sensor) to determine the volume of air entering the intake manifold.
GEMS throttle circuitry is adaptable within a range of 80 to 500 mV . Within this range, the PCM will adapt to the initial setting and use it as a reference. There is no need to adjust the TPS following installation on these models. If the TPS should fail, the ECM will use a default value of 576 mV and the MIL will be illuminated.
A diagnostic trouble code is set when sensor output is less than 78 mV for longer than 160 milliseconds .
Acceleration Enhancement
The ECM increases the amount of fuel normally provided for a given throttle position during periods of peak acceleration. This allows the system to anticipate fuel needs.
Deceleration Fuel Shut-off
During throttle closed deceleration, the ECM does not activate fuel injectors (zero pulse-width) to prevent unneeded fuel from entering the cylinders. This strategy protects against catalytic converter overheating and reduces fuel consumption.
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TReK
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Mass air flow sensor (MAF Sensor)
The "hot wire" type mass air flow sensor is mounted rigidly to the air filter and connected by flexible hose to the plenum chamber inlet. The sensing element of the MAF Sensor is a hot wire anenometer consisting of two wires, a sensing wire which is heated and a compensating wire which is not heated. Air flows across the wires cooling the heated one, changing its resistance. The ECM measures this change in resistance and calculates the amount of air flowing into the engine.
As there is no default strategy, failure will result in the engine starting, and dying when it reaches 550 rev/min, when the ECM detects no MAF Sensor signal. The fault is indicated by illumination of the malfunction indicator light (MIL) on North American specification vehicles.
The "hot wire" type mass air flow sensor is mounted rigidly to the air filter and connected by flexible hose to the plenum chamber inlet. The sensing element of the MAF Sensor is a hot wire anenometer consisting of two wires, a sensing wire which is heated and a compensating wire which is not heated. Air flows across the wires cooling the heated one, changing its resistance. The ECM measures this change in resistance and calculates the amount of air flowing into the engine.
As there is no default strategy, failure will result in the engine starting, and dying when it reaches 550 rev/min, when the ECM detects no MAF Sensor signal. The fault is indicated by illumination of the malfunction indicator light (MIL) on North American specification vehicles.
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TReK
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From: Ketchikan, Alaska, USA
Camshaft position sensor (CMP Sensor)
The camshaft position sensor is located in the engine front cover. It produces one pulse every two revolutions. The signal is used in two areas, injector timing corrections for fully sequential fuelling and active knock control.
If the camshaft sensor fails, default operation is to continue normal ignition timing. The fuel injectors will be actuated sequentially, timing the injection with respect to top dead centre. Injection will either be correct or one revolution out of synchronization. The fault is not easily detected by the driver. The fault is indicated by illumination of the malfunction indicator light (MIL) on North American specification vehicles.
The camshaft position sensor is located in the engine front cover. It produces one pulse every two revolutions. The signal is used in two areas, injector timing corrections for fully sequential fuelling and active knock control.
If the camshaft sensor fails, default operation is to continue normal ignition timing. The fuel injectors will be actuated sequentially, timing the injection with respect to top dead centre. Injection will either be correct or one revolution out of synchronization. The fault is not easily detected by the driver. The fault is indicated by illumination of the malfunction indicator light (MIL) on North American specification vehicles.
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TReK
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From: Ketchikan, Alaska, USA
Crankshaft position sensor (CKP Sensor)
The crankshaft position sensor is the most important sensor on the engine. It is located in the left hand side of the flywheel housing and uses a different thickness of spacer for manual and automatic gearboxes.
The signal it produces informs the ECM:
The crankshaft position sensor is the most important sensor on the engine. It is located in the left hand side of the flywheel housing and uses a different thickness of spacer for manual and automatic gearboxes.
The signal it produces informs the ECM:
- The engine is turning.
- How fast the engine is turning.
- Which stage the engine is at in the cycle.
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TReK
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KNOCK SENSORS
A pair of knock sensors monitors engine noise and vibration for the ECM. Engine knock is often caused by detonation or pre-ignition which can damage pistons and valves. The ECM is able to identify the characteristics of engine knock and retard ignition timing when knock is present. The ability to sense engine knock allows the ECM to operate the engine close to its limits of ignition advance. This is the most efficient ignition timing for maximum performance and fuel economy.
The sensors are mounted in the cylinder block located between cylinders 3 and 5 and between cylinders 4 and 6. Positioning a sensor in each bank of cylinders allows the ECM to precisely identify which of the eight cylinders is knocking.
A pair of knock sensors monitors engine noise and vibration for the ECM. Engine knock is often caused by detonation or pre-ignition which can damage pistons and valves. The ECM is able to identify the characteristics of engine knock and retard ignition timing when knock is present. The ability to sense engine knock allows the ECM to operate the engine close to its limits of ignition advance. This is the most efficient ignition timing for maximum performance and fuel economy.
The sensors are mounted in the cylinder block located between cylinders 3 and 5 and between cylinders 4 and 6. Positioning a sensor in each bank of cylinders allows the ECM to precisely identify which of the eight cylinders is knocking.
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TReK
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From: Ketchikan, Alaska, USA
INTAKE AIR TEMPERATURE SENSOR (X311)
The Intake Air Temperature Sensor is a dedicated sensor, mounted on the air cleaner housing. The Intake Air Temperature Sensor is a resistive sensor, i.e. the change in resistance is related to change in air temperature. The signal from the Intake Air Temperature Sensor (X311) is used to retard the ignition timing if the air temperature rises above 55°C .
The Intake Air Temperature Sensor is a dedicated sensor, mounted on the air cleaner housing. The Intake Air Temperature Sensor is a resistive sensor, i.e. the change in resistance is related to change in air temperature. The signal from the Intake Air Temperature Sensor (X311) is used to retard the ignition timing if the air temperature rises above 55°C .
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TReK
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HEATED OXYGEN SENSORS
The Heated Oxygen Sensor (H02S ) mounted in the exhaust downpipe serves as the key input in an electronic fuel injection system. The sensor is used by the ECM to determine the amount of oxygen present m the exhaust gas. The ECM uses this information to increase or decrease injector open time to bring the air/fuel ratio as close to Stoichiometric as possible.
Additional oxygen sensors are mounted in the exhaust system, downstream from each of the vehicle's catalytic converters. Data from these new sensors is compared with the signal produced by the front sensor on each bank. This information is used by the GEMS to monitor performance of the Three-Way Catalyst (TWC ).
The rear sensors are also part of the ECM's fuel system back-up strategy. Should the signal from the front HO2S fail, the signal from the corresponding rear sensor will be used so that the vehicle can remain in closed-loop operation.
All Land Rover systems use sensors that change resistance in the presence of oxygen in the exhaust. The ECM is able to calculate the amount of oxygen in the exhaust based on this change.
Both types of oxygen sensor signals are continually "switching" as the ECM changes injector pulse width in response to the sensor messages. On systems with more than one sensor, the ECM monitors each sensor separately. Fuel trim adjustments are made independently to each cylinder bank, or individual cylinder, depending on the fuel system.
Oxygen sensors operate efficiently only when warm. Sensors include heaters to help them reach operating temperatures quickly. This allows the sensors to provide accurate information to the ECM soon after start-up and the system to enter closed loop operation (based on sensor inputs) sooner. Closed loop operation helps provide an efficient fuel mixture and controls emissions when the engine is cold. Closed loop also guards against catalytic converter overheating from the introduction of too much fuel.
In their operating environment, oxygen sensors are quite durable. However, they are easily damaged if dropped, exposed to excessive heat, or contaminated. Care should be taken when handling oxygen sensors.
Be careful when replacing an oxygen sensor. Contamination of the sensor body can lead to premature failure. The sensor threads must be sealed with the material provided to ensure there are no oxygen leaks. Do not use silicone sealants for this purpose as they will contaminate the sensor.
The Heated Oxygen Sensor (H02S ) mounted in the exhaust downpipe serves as the key input in an electronic fuel injection system. The sensor is used by the ECM to determine the amount of oxygen present m the exhaust gas. The ECM uses this information to increase or decrease injector open time to bring the air/fuel ratio as close to Stoichiometric as possible.
Additional oxygen sensors are mounted in the exhaust system, downstream from each of the vehicle's catalytic converters. Data from these new sensors is compared with the signal produced by the front sensor on each bank. This information is used by the GEMS to monitor performance of the Three-Way Catalyst (TWC ).
The rear sensors are also part of the ECM's fuel system back-up strategy. Should the signal from the front HO2S fail, the signal from the corresponding rear sensor will be used so that the vehicle can remain in closed-loop operation.
All Land Rover systems use sensors that change resistance in the presence of oxygen in the exhaust. The ECM is able to calculate the amount of oxygen in the exhaust based on this change.
Both types of oxygen sensor signals are continually "switching" as the ECM changes injector pulse width in response to the sensor messages. On systems with more than one sensor, the ECM monitors each sensor separately. Fuel trim adjustments are made independently to each cylinder bank, or individual cylinder, depending on the fuel system.
Oxygen sensors operate efficiently only when warm. Sensors include heaters to help them reach operating temperatures quickly. This allows the sensors to provide accurate information to the ECM soon after start-up and the system to enter closed loop operation (based on sensor inputs) sooner. Closed loop operation helps provide an efficient fuel mixture and controls emissions when the engine is cold. Closed loop also guards against catalytic converter overheating from the introduction of too much fuel.
In their operating environment, oxygen sensors are quite durable. However, they are easily damaged if dropped, exposed to excessive heat, or contaminated. Care should be taken when handling oxygen sensors.
Be careful when replacing an oxygen sensor. Contamination of the sensor body can lead to premature failure. The sensor threads must be sealed with the material provided to ensure there are no oxygen leaks. Do not use silicone sealants for this purpose as they will contaminate the sensor.
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TReK
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Vss
An intermittent VSS fault is identified by a freeze frame speed of above 110 mph (an input to GEMS caused by a noisy signal from the VSS), complaints of intermittent power loss, or engine stall.
NOTE: On TestBook disc DRG 0001 and DRG0002 the road speed displayed as "MPH" is actually a kilometers per hour value, NOT miles per hour. A TestBook reading of "177 MPH" is actually 177 kph. This reading, when converted to the desired mile per hour reading, is 110 mph. One of the functions of the VSS signal to the GEMS unit is to provide information on vehicle speed. If the GEMS unit sees an excessively high speed (above 110 mph) it will initiate fuel cut off to the odd cylinders momentarily to reduce engine power. This feature is intended to prevent the driver from operating the vehicle at excessive road speeds.
Customer complaints of intermittent engine surging at highway speeds, inoperative or fluctuating speedometer, or a MIL illumination could be caused by an intermittently failing VSS.
If the MIL is illuminated with misfire codes P0300, P1316 and any combination of P0301, P0303, P0305 and P0307 stored or if the customer complaint is surging, hesitation, or loss of power at highway speeds, pay close attention to the freeze frame data, particularly engine rpm and road speed.
NOTE: As with all electrical diagnosis, the circuit between the sensor and the GEMS unit should be checked. The technician should be aware of the fact that the sensor test will not detect an intermittently failing sensor. If the freeze frame data shows a road speed that does not conform to the engine speed (for example 110 mph at 2000 rpm or a road speed of 0 mph), an intermittent fault with the VSS could be the problem.
If inconsistencies between engine speed and vehicle speed are observed, replace the sensor. See attached DTCR samples
NOTE: On TestBook disc DRG 0001 and DRG0002 the road speed displayed as "MPH" is actually a kilometers per hour value, NOT miles per hour. A TestBook reading of "177 MPH" is actually 177 kph. This reading, when converted to the desired mile per hour reading, is 110 mph. One of the functions of the VSS signal to the GEMS unit is to provide information on vehicle speed. If the GEMS unit sees an excessively high speed (above 110 mph) it will initiate fuel cut off to the odd cylinders momentarily to reduce engine power. This feature is intended to prevent the driver from operating the vehicle at excessive road speeds.
Customer complaints of intermittent engine surging at highway speeds, inoperative or fluctuating speedometer, or a MIL illumination could be caused by an intermittently failing VSS.
If the MIL is illuminated with misfire codes P0300, P1316 and any combination of P0301, P0303, P0305 and P0307 stored or if the customer complaint is surging, hesitation, or loss of power at highway speeds, pay close attention to the freeze frame data, particularly engine rpm and road speed.
NOTE: As with all electrical diagnosis, the circuit between the sensor and the GEMS unit should be checked. The technician should be aware of the fact that the sensor test will not detect an intermittently failing sensor. If the freeze frame data shows a road speed that does not conform to the engine speed (for example 110 mph at 2000 rpm or a road speed of 0 mph), an intermittent fault with the VSS could be the problem.
If inconsistencies between engine speed and vehicle speed are observed, replace the sensor. See attached DTCR samples
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TReK
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From: Ketchikan, Alaska, USA
Ecm
Description
The V8 engine for models prior to 99MY is controlled by a Sagem GEMS engine management system. The ECM uses sensors to determine ambient conditions and operating data and uses this data and the information stored in an internal memory map to control the electronic ignition and fuel injection. The system features idle speed control, fault monitoring, security immobilisation and engine load management functions. GEMS can be interrogated via the diagnostic socket to access fault codes and other diagnostic information using Testbook.
The engine management system (EMS) maintains optimum engine performance over the entire operating range. The correct amount of fuel is metered into each cylinder inlet tract and the ignition timing is adjusted at each spark plug. The system is controlled by the engine control module (ECM) which receives data from sensors located on and around the engine. From this information it provides the correct fuel requirements and ignition timing at all engine loads and speeds.
The fuel injection system uses a hot wire mass air flow (MAF) sensor to calculate the quantity of air flowing into the engine.
The ignition system does not use a distributor. It is a direct ignition system (DIS), using four double ended coils. The circuit to each coil is completed by switching inside the ECM.
The on-board diagnostic system detects any faults which may occur within the EMS. Fault diagnosis includes failure of any EMS sensors and actuators, emissions related items, fuel supply and exhaust systems.
The system incorporates certain default strategies to enable the vehicle to be driven in case of sensor failure. This may mean that a fault is not detected by the driver. The fault is indicated by illumination of the malfunction indicator light (MIL) on North American specification vehicles.
A further feature of the system is "robust immobilisation", fitted to European specification vehicles. Upon arming the alarm, the EMS ECM disables the injectors and the Body electrical Control Module (BeCM) inhibits the crank relay (the vehicle cannot be started until the alarm is disarmed).
CAUTION: System sensor connectors can be contaminated by oil or coolant when disconnected during repair or testing. Use a suitable cap to prevent dirt or fluid ingress.
The V8 engine for models prior to 99MY is controlled by a Sagem GEMS engine management system. The ECM uses sensors to determine ambient conditions and operating data and uses this data and the information stored in an internal memory map to control the electronic ignition and fuel injection. The system features idle speed control, fault monitoring, security immobilisation and engine load management functions. GEMS can be interrogated via the diagnostic socket to access fault codes and other diagnostic information using Testbook.
The engine management system (EMS) maintains optimum engine performance over the entire operating range. The correct amount of fuel is metered into each cylinder inlet tract and the ignition timing is adjusted at each spark plug. The system is controlled by the engine control module (ECM) which receives data from sensors located on and around the engine. From this information it provides the correct fuel requirements and ignition timing at all engine loads and speeds.
The fuel injection system uses a hot wire mass air flow (MAF) sensor to calculate the quantity of air flowing into the engine.
The ignition system does not use a distributor. It is a direct ignition system (DIS), using four double ended coils. The circuit to each coil is completed by switching inside the ECM.
The on-board diagnostic system detects any faults which may occur within the EMS. Fault diagnosis includes failure of any EMS sensors and actuators, emissions related items, fuel supply and exhaust systems.
The system incorporates certain default strategies to enable the vehicle to be driven in case of sensor failure. This may mean that a fault is not detected by the driver. The fault is indicated by illumination of the malfunction indicator light (MIL) on North American specification vehicles.
A further feature of the system is "robust immobilisation", fitted to European specification vehicles. Upon arming the alarm, the EMS ECM disables the injectors and the Body electrical Control Module (BeCM) inhibits the crank relay (the vehicle cannot be started until the alarm is disarmed).
CAUTION: System sensor connectors can be contaminated by oil or coolant when disconnected during repair or testing. Use a suitable cap to prevent dirt or fluid ingress.
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TReK
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From: Ketchikan, Alaska, USA
Bcm
Multi-Function Unit - Self-Test
The multi-function unit is located at the rear of the in-car fuse box on the 1995 Classic and on all Discoverys. It's purpose is to operate/control a number of vehicle functions and eliminates the need for multiple individual control units.
Input tests:
With the system still in diagnostic mode, press and release the rear defroster switch again - now the MFU will provide output signals to the components which will then operate
The multi-function unit is located at the rear of the in-car fuse box on the 1995 Classic and on all Discoverys. It's purpose is to operate/control a number of vehicle functions and eliminates the need for multiple individual control units.
Input tests:
- Switch ignition "off"
- Press and hold rear defrost switch then switch on ignition (position 2)-release defroster switch (Note: Release the defroster switch within one second of turning on ignition).
- A series of beeps indicates that the MFU is in diagnostic mode.
- Perform input checks by operating the following switches/controls. A correct input is indicated with a two beep tone.
- Windshield defrost (Classic only)
- Rear window defrost
- Open and close doors and tailgate
- Operate parking/headlamps switch
- Wiper switch in intermittent position
- Windshield/headlamps wash switch
- Rear wiper switch
- Drivers seat belt latch
- Rear fog lamp switch ('97 Discovery only)
With the system still in diagnostic mode, press and release the rear defroster switch again - now the MFU will provide output signals to the components which will then operate
- Rear window defroster and dash indicator lamps
- Interior lamp
- Headlamp wash (not Defender)
- Front and rear wipers
- Chime and seat belt indicator lamps
- Rear fog lamps ('97 Discovery)
- Windshield heater ('95 Classic)
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