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08/03/2005

 

Component Monitor

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Comprehensive Component Monitor

Hardware checks in EECV software

The EECV module uses software to monitor the main system components. The diagnostic system could not be efficient if a test ran using faulty sensors and so every one is checked by the EECV before a Monitor uses it for a test: these are shown as Sensors Checked and OK on the various Monitor pages. The program that runs this diagnostic is called the Comprehensive Component Monitor, (CCM) and the CCM is one of the three Monitors that runs all the time the vehicle is being used.

Smart Drivers in the EECV are able not only to switch sensors on and off and to receive signals, but they can also check the connected pin for opens, shorts and out of range values by monitoring the analogue-to-digital input values. This enables a full error check without using additional hardware - a very elegant solution.

The CCM only runs checks on actuators and sensors not checked by their own Monitors - examples are EGR and HO2S sensors: these are excluded from the CCM.

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Comprehensive Component Monitor - 

ENGINE SENSORS

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MASS AIR FLOW (MAF) SENSOR

P0102   Mass or Volume Air Flow Circuit Low Input

P0103   Mass or Volume Air Flow Circuit High Input 

These codes are self-explanatory:- during the test the Comprehensive Component Monitor checked the input voltage of the MAF and found it to be too high or low.

Typical error value: <0.20V and >4.80V

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MASS AIR FLOW CIRCUIT TESTS

The following codes are self explanatory and may be found where wiring faults have interrupted data to the EECV.

P0100  Mass or Volume Air Flow Circuit Malfunction

P0101   Mass or Volume Air Flow Circuit Range/Performance Problem 

P0104   Mass or Volume Air Flow Circuit Intermittent

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MAF/TP RATIONALITY CHECK

The CCM also carries out a rationality check on the reading from the MAF and the Throttle Position Sensor together, since the reading from one should be proportional to the other. For this check the CCM uses the LOAD value, which is calculated by the EECV from the MAF input, gear and other data. 

NOTE, this DTC failure might also refer to the MAF, not just to the TP. Check connections to both, clean the MAF   and be prepared to test it

P1121 Throttle Position Sensor out of range

Conditions:  RPM between 1000 and 3800 rpm, Engine Coolant at least 100F

Typical fault thresholds:

Load >60% and TP <2.4 V

Load <30% and TP>2.4 V

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THROTTLE POSITION (TP) sensor

P0122   Throttle Position Sensor Circuit Low Input

P0123   Throttle Position Sensor Circuit High Input

The Throttle Position Sensor is a rotary potentiometer with a resistive element that varies linearly and in direct proportion to the throttle plate angle.  The TP sensor circuit is checked in a test lasting 5 seconds.

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ENGINE COOLANT TEMPERATURE (ECT) 

The ECT sensor is a temperature sensitive resistor (thermistor) connected to the internal resistor network in the Powertrain Control Module, the EECV, and it provides a output voltage inversely proportional to the engine coolant temperature. The PCM uses this input to modify ignition timing, EGR flow and air/flow ratio.

P0117   Engine Coolant Temperature Circuit Low Input

P0118   Engine Coolant Temperature Circuit High Input

Typical Malfunction Thresholds: Voltage <0.20V or Voltage >4.80 V

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AIR INLET TEMPERATURE (AIT) 

P0112   Intake Air Temperature Circuit Low Input

P0113   Intake Air Temperature Circuit High Input

The IAT sensor is a temperature sensitive resistor (thermistor) connected to the internal resistor network in the Powertrain Control Module, the EECV, and it provides a output voltage inversely proportional to the intake air temperature. The PCM uses this input as a corrector for airflow calculations, to proportion the cold enrichment fuel flow and to modify spark advance.

Typical Malfunction Thresholds: Voltage <0.20V or Voltage >4.80 V

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Comprehensive Component Monitor - 

IGNITION SYSTEM

On the Scorpio OBDII engines the Electronic Distributorless Ignition System (EDIS) systems are used. On the DOHC engines the spark modules are built over 2 of the spark plugs. On the 24V the ED is placed at the front of Bank 1 beneath the Cosworth intake cover, and the Ignition module is on the offside wing behind the headlamp.

IGNITION SIGNAL PROCESSING

The EDIS system uses a chip to process the 36 or 40 tooth crankshaft position signal from the CKP, this generates a low data-rate Profile Ignition Pickup (PIP) signal for the PCM and provides control of the 4 or 6 terminal coil pack which fires a pair of spark plugs. One of the sparkplugs is on the compression stroke and the other the exhaust stroke.

CCM checks the ignition system by monitoring three ignition signals:

bulletThe PIP signal generated by the CKP - the timing reference signal. PIP is a 50% duty cycle, square-wave signal with a rising edge at 10 BTDC.
bulletCamshaft IDentification (CID) signal derived from the CaMshaft Position sensor (CMP). This identifies #1 cylinder.
bulletIgnition Diagnostic Monitor (IDM) a signal that indicates that the primary side of the ignition coil has fired. This signal is received as a digital pulse width signal from the EDIS chip. The EDIS chip determines if the current flow to the ignition coil reaches the required current (typically 3 to 4 Amps for DIS) within a specified time period, normally >200 microseconds. 

CKP CHECK

First, the relationship between PIP signals is evaluated to determine that the PIP signal is rational. Too large a change between 3 successive PIP indicates a noisy or missing PIP signal:

P0320 Ignition/Distributor Engine Speed Input Circuit Malfunction

Check the connection and wiring to the CKP sensor. Be prepared to replace this sensor.

CMP CHECK

Next, the CMP edge count is compared to the PIP edge count. If the proper ratio of CMP to PIP events is not being maintained (ie one CMP edge compared to 4 or 6 PIP events, depending on engine cylinders) it indicates a missing or noisy CMP signal:

P0340 Camshaft Position Sensor Circuit Malfunction

Check the connection and wiring to the CMP sensor. Be prepared to replace this sensor.

Ignition Diagnostic Monitor (IDM) CHECK

Finally, the relationship between IDM edges and PIP edges are evaluated. If there is not an IDM edge (coil event) for every PIP edge (commanded spark event) the PCM will search for a pattern of failed IDM events to determine which ignition coil has failed. If the engine is running and there are no IDM edges, the IDM circuit is malfunctioning. NOTE: The IDM is not a Monitor in the OBD sense, like the Catalyst Monitor - it is a signal from the EDIS chip and in this respect is poorly named.

P0351 Ignition Coil A Primary/Secondary Circuit Malfunction 

P0352 Ignition Coil B Primary/Secondary Circuit Malfunction 

Check connections and wiring to the spark modules (particularly DOHC models where the Fuel Cut-Off Loom has proved vulnerable to cracking).

Be prepared to replace spark modules.

NOTE: These DTCs may also be accompanied by Misfire codes P0300 or P0301 to P0306.

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BAROMETRIC PRESSURE SENSOR - BARO

The Barometric Pressure Sensor is often tucked away at the rear of the engine bay beneath the passenger's feet. Unless one is looking for it you would never know the car was equipped with such a device but the EECV uses the BARO sensor to make adjustments to the fuelling to compensate for atmospheric pressure.

The BARO is a silicon capacitive absolute pressure sensor with signal conditioning electronics which produces a 50% duty wave form whose frequency is proportional to the pressure input.

P1792     Barometer Pressure Circuit Malfunction

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Comprehensive Component Monitor - 

ENGINE OUTPUTS

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IDLE AIR CONTROL (IAC) Valve

The EECV Powertrain Control Module (PCM) controls the idle of the engine by means of Spark Advance, the INJector duration, and by controlling the flow of air through the Air Bypass Pipe at the throttle body. The IACV is mounted at the throttle body and moderates the flow of air bypassing the throttle plate. The IAC is actually a solenoid which controls the position of a pintle valve, position of which is directly related to the current through the solenoid. By varying this current, the pintle can maintain any position from fully closed to fully open.

The IAC is checked electrically for open and shorts.

P0505 or P1504 Idle Air Control Circuit Malfunction

P1508 Idle Air Control Circuit Open

P1509 Idle Air Control Circuit Shorted

The IAC is also checked by monitoring the closed loop idle correction speed required to maintain the desired idle rpm. This monitor runs once per driving cycle for 30 seconds. The test cannot run before 30 seconds after start up and if the ECT must show a temperature of at least 150 F, and the engine must be in Closed Loop.

If the proper idle rpm cannot be maintained:

The engine shows a high RPM (+100 over target):

P0507 or P1507 Idle Control System RPM Higher Than Expected

The engine shows a low RPM (-200 rpm under target.)

P0506 or P1506 Idle Control System RPM lower Than Expected

The causes of an unsteady/rolling idle have kept the Confidential List busy on many occasions. Usually the cause is found to be a leak in the vacuum/inlet system. The following should be checked carefully:

bulletinlet system, O rings on 24V especially after work on the engine
bulletvacuum system pipework, damaged or disconnected vacuum system pipes
bulletdamaged or loose throttle air bypass pipe
bulletfaulty EVAP solenoid or EVR valve
bulletloose petrol filler cap

IACV Flush

The usual advice carried from experience with the Granada is to flush the IAC valve through with petrol or carb cleaner. However, this usually applied to unsteady idle/stalling when hot and there is little evidence that what applied to the older EECIV system has the same effect on the more complex EECV - cleaning the IAC valve has usually had no effect whatsoever, although it may still be relevant on the 12V Scorpio (which still uses the EECIV). In fact the Idle Control on the Scorpio EECV is holistic enough to maintain engine idle even with the throttle bypass pipe blocked, using just ignition and injection timing.

Vacuum System

The vacuum system consists of tappings into the inlet manifold where small bore pipes are open to engine depression. The inlet pipe is connected to the vacuum reservoir mounted on the drivers side of the engine bay via the Electronic Vacuum Regulator mounted on the same side behind the offside headlamp. The EVR regulates the vacuum in the reservoir by opening a valve between the reservoir and the inlet manifold. This vacuum is the motive force for the VIS actuator valve (24V Cosworth and DOHC 16V 2L), the A/C vent doors and the EGR valve mounted on the inlet manifold. A separate EVR regulates this vacuum for the EVAP system. High and rolling idle rpm can be caused by a leak in any of these pipes and connections and so they need to be checked carefully for security or damage. 

The EVAP and EVR regulators if faulty may result in an unmetered leak. These are checked regularly and should generate DTCs.

Throttle Air Bypass Pipe

The air bypass pipe (through which the IAC valve meters air into the Inlet Manifold in order to regulate idle) has been found to have caused a rolling idle when damaged and/or loose. This should be inspected carefully.

Petrol Cap

Sometimes a racing idle is caused by a loosely-fitted petrol cap, or an improper one. The correct cap should be able to sustain a vacuum for EVAP. This can be checked using an OBD lead and VE software.  If EVAPCVA (VMV fault detected) shows YES then the system has detected a leak, NO if there is not a problem. On several occasions on a high idle I have found this address showing YES and tightened the petrol cap against its ratchet, returned to the OBD for another scan and found this address showing NO. On the next complete Drive Cycle the idle returned to normal, so this is always worth checking.

ECT Influence

For a persistent high idle check the ECT using a multimeter, and monitor it with VE software. A faulty ECT permanently reading low has a double influence on the idle RPM. The ECT is used for fuelling information and this will effect combustion, while a faulty ECT showing lower than 150 F will also prevent the Idle speed check from running.

Why No DTCs?

Some owners have been perplexed when their engine has developed a racing idle, clearly above the OBD target, and yet they have found no DTCs recorded when they logged in with the OBD. I have to remind them that OBD will find no DTCs if it is not running, e.g.,

bulletThe engine has just started, less than 30 seconds
bulletVehicle system voltage is less than 11 volts

In addition, the idle test requires more parameters to be met before it executes, e.g.

bulletA Drive Cycle - a 2 minute run down to the shops doesn't cut it
bulletClosed loop fuelling - faulty pre-cat HO2S sensors usually means Open Loop fuelling
bulletEngine cold - faulty thermostat keeps engine too cool
bulletECT faulty - not showing above 150 F

Finally, remember that the CCM only runs the Idle Test once per OBD Trip.

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Fuel Injectors - INJ

The injectors are mounted in the pressurised fuel rail, one injector for each cylinder. The injection system for the Scorpio with EECV is multipoint sequential fuel injection - the fuel is injected for each cylinder at the correct time for the induction stroke.

The injectors are electromechanical devices that meter and atomise the fuel delivered into the inlet and they are mounted in the lower intake manifold, positioned so that their tips are directing fuel just upstream of the intake valves.

The injector is a solenoid that actuates a normally closed needle valve assembly. The fuel rail into which the injector is set contains fuel maintained at a constant fuel pressure by the fuel regulator, so fuel flow is regulated only by how long the injector remains open. An electrical signal from the EECV PCM activates the solenoid and lifts the pintle from its seat allowing the fuel through the orifice, which is contoured to atomize the fuel.

First the CCM monitors the INJector circuit for opens and shorts:

P0200   Injector Circuit Malfunction 

Then the CCM monitors each of the INJector  events

P0201   Injector Circuit Malfunction - Cylinder 1

P0202   Injector Circuit Malfunction - Cylinder 2

P0203   Injector Circuit Malfunction - Cylinder 3

P0204   Injector Circuit Malfunction - Cylinder 4

P0205   Injector Circuit Malfunction - Cylinder 5

P0206   Injector Circuit Malfunction - Cylinder 6

Check the connector to the INJector producing a code and examine the wiring on the engine control loom - especially the DOHC models where the Fuel Cut Off (cylinder head) loom has proved vulnerable to cracked insulation.

NOTE: 

bulletDO NOT APPLY BATTERY VOLTAGE to the injectors during any kind of diagnostics.
bulletDTCs apply to electrical checks only. Gummed INJectors may not atomize the fuel sufficiently to cause a thorough combustion and this will not generate an Injector DTC.
bulletINJector malfunction may also generate a Misfire DTC.

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Comprehensive Component Monitor - 

TRANSMISSION

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Although there is no MIL light on the Scorpio there is a Transmission Indicator Light (TIL) - this is the Overdrive (O/D light. When this flashes the EECV has detected a hardware fault within the autobox and is alerting the driver of impaired function. The EECV may be able to 'program out' a solenoid and not call it during gear changes in order to minimise damage to the transmission, and if the EPC valve has failed the PCM will restrict the power that the engine develops - 'LOS'. In the meantime Transmission DTCs are recorded by the EECV.

OTHER CAUSES

Transmission DTCs can be generated by problems not caused by the autobox. The following should be checked first, in this order:

bulletDirty MAF sensor. see Clean the MAF
bulletFaulty MAF sensor, see Faulty Maf
bulletWet/damaged multiplugs on autobox see Looms
bulletFaulty Fuel Cut-off Loom on DOHC engines Cutoff
bulletPre June 1996 vehicles, faulty Arnitel wiring on the thin-walled insulated control looms between the PCM and the engine and gearbox see chafed

LIMITED OPERATION STRATEGY (LOS)

If the EECV PCM detects an fault that endangers the gearbox it will flash the TIL and engage LOS mode. This is also known as 'Limp-Home Mode' because the intention is that the vehicle can still be driven - at drastically reduced performance - so as to arrive at the nearest Ford main dealer without delay.

During LOS the PCM will only allow the engine to develop enough torque to reach a low speed, perhaps up to 20mph even flooring the accelerator. The spark advance is set exactly to 10 BTDC, regardless of load or revs, and the INJector duration is fixed to minimum fuelling. The effect of this programming is that the cooling fans run constantly while the ignition is on - this is a tell-tale sign, which together with the steamroller performance and the flashing TIL, leaves the owner no choice but to seek diagnosis .

If LOS is experienced in a Scorpio then the DTCs need to be downloaded from the PCM. This can be done (at a cost) by a Ford main dealer, but also free of charge by an owner equipped with an OBD lead.

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TRANSMISSION RANGE SENSOR (TRS) 

The TRS is also known as the PRNGL switch. In fact it is a variable resistor, not a switch, and on EECV equipped Scorpios it moderates the 5V signal voltage to high with a low resistance in position 1 to the lowest voltage with the highest resistance in P.

The TRS is tested in any or each position for 30 seconds. Opens and shorts, performance and high and low inputs may all generate a DTC:

P0705   Transmission Range Sensor Circuit malfunction

P0706   Transmission Range Sensor Circuit Range/Performance

P0707   Transmission Range Sensor Circuit Low Input

P0708   Transmission Range Sensor Circuit High Input

P0709   Transmission Range Sensor Circuit Intermittent 

Typical thresholds are > 4.8 or < 0.2 V. The TRS is the module on the passenger side of the A4LDE gearbox just to the rear of the gearchange fulcrum.  

NOTE: Check also the linkage from the gear lever to the gearchange fulcrum to ensure that the indicated gear is actually being selected.

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TRANSMISSION FLUID TEMPERATURE (TFT) Sensor

The EECV powertrain control module uses analog input from the TFT sensor to check that the temperature of the transmission is within safe parameters. If the temperature is too low or too high the EECV will prevent the Torque Converter Clutch from engaging. This will be noticeable as a failure to lockup and a higher rpm at cruising speed than usual.

In the event of a failure of the TFT the EECV will subsitute the data from the ECT, so it is possible that the TFT sensor may have failed and that there are no symptoms apart from DTCs - until a problem with the ECT itself then causes strange autobox behaviour.

The DTCs for the TFT may be:

P0710   Transmission Fluid Temperature Sensor Circuit Malfunction

P0711   Transmission Fluid Temperature Sensor Circuit Range/Performance

P0712   Transmission Fluid Temperature Sensor Circuit Low Input

P0713   Transmission Fluid Temperature Sensor Circuit High Input

P0714    Transmission Fluid Temperature Sensor Circuit Intermittent  

The TFT is built into the valve chamber of the autobox. Most owners would prefer to use an autobox specialist to replace the sensor. 

Typical failure parameters: Reading < 0.05V or > 4.6 V

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TURBINE SHAFT SPEED (TSS) Sensor

VEHICLE SPEED SENSOR (VSS)

Both the VSS and the TSS are Hall devices: the VSS is external to the gearbox connected to the final drive shaft, but the TSS is mounted internally in the intermediate planet carrier. They provide the PCM with reference data for the rpm of the autobox internals. Using both the VSS and the TSS input, the PCM can lessen the torque from the engine at the moment of shifting to smooth out the change.

The CCM checks both these inputs for rationality. If the engine RPM is above the Torque Converter stall speed and the engine LOAD is also high then the PCM infers that the vehicle is moving. 

If there is insufficient output from the VSS, then 

P0500 Vehicle Speed Sensor circuit malfunction

The VSS is on the offside of the gearbox and secured with a single bolt. It can be replaced quite simply, but access to the underside of the car is required and it may be necessary to lower the exhaust and/or heatshielding, depending on engine.

If there is insufficient input from the TSS, then

P0715    Turbine Speed Sensor Circuit Malfunction  

In the case of the TSS, this is mounted on a planet carrier and would not be accessible to the average owner - an autobox specialist would be needed for a replacement.

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SHIFT SOLENOIDS - ELECTRICAL

The shift solenoid (SS) output circuits are checked for opens and shorts by the PCM. As usual, it does this by monitoring the feedback circuit from the output driver internally in software. 10 shift events are monitored. 

Entry Conditions: Transmission Fluid Temp between 70 and 225 F and positive driving torque.

Depending on the reading software, these solenoids may be shown as SSA to SSD, or SS#1 etc. A detected open or short is reported by the DTCs

P0750   Shift Solenoid A Malfunction

P0755   Shift Solenoid B Malfunction

P0760   Shift Solenoid C Malfunction 

for each of the shift solenoids. Those are the electrical checks. Next, the Mechanical checks.

SOLENOIDS - MECHANICAL FUNCTION:

The solenoids are also checked for mechanical function. During a sample of 10 shift events the PCM calculates the gear ratio for each shift during positive driving torque and monitors the VSS and TSS. The actual gear ratio can be computed and compared with the predicted gear ratio in memory in order to determine the actual gear pattern obtained during the upshift sequence. In this way a malfunctioning solenoid can be determined; for example a shift sequence 1-2-3-4 which produces a 2-2-4-4 pattern identifies that SSA is shorted to power or hydraulically stuck.

P0751   Shift Solenoid A Performance or Stuck Off/1-2 Shift Solenoid Valve Performance

P0756   Shift Solenoid B Performance or Stuck Off/2-3 Shift Solenoid Valve Performance

P0761   Shift Solenoid C Performance or Stuck Off/3-4 Shift Solenoid Valve Performance

Owner action is usually limited to seeking the services of an autobox specialist. In the case of Solenoid failure these can sometimes be repaired with the gearbox still in the car: the solenoids are accessible on the nearside of the autobox. On 16V vehicles the solenoids can be close to the exhaust and in very hot weather this may cause the solenoid to stick.

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CCM - TORQUE CONVERTER CLUTCH (TCC)

The Torque Converter Clutch locks the input to output together during low-torque periods of driving. This lowers RPM and saves petrol as well as engine wear and tear. The TCC is a duty-cycle between 0 and 200% and is controlled directly by the  PCM.

There are both Electrical -

P0743   Torque Converter Clutch Circuit Electrical

and Mechanical checks -

P1744   Torque Converter Clutch System Performance

The following conditions have to be met before the CCM runs the TCC check:

Conditions: Transmission Fluid Temp between 70 and 225 F and positive driving torque. The Electric check needs a Commanded TCC duty cycle of 60 to 90% with 0 RPM slip, while the mechanical check requires 60 to 100% for 0 rpm slip. The TCC is not checked while the gearbox is shifting gears.

If the output Driver feedback circuit does not match the commanded driver state (> 1 volt if commanded on, <2 volts if commanded off,) the P0743 DTC is recorded. If the slip across the torque converter >100 rpm (or on some application the speed ratio <0.93%) then P1744 is recorded.

Owner action is limited to seeking the services of an autobox specialist.

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ELECTRONIC PRESSURE CONTROL (EPC) Solenoid

The hydraulic pressure required by the actuators, clutches and brake bands is provided by a transmission fluid pump mounted on the input shaft. The line pressure in the system is controlled by the PCM using a duty-cycled variable-force solenoid, the EPC. 

The EPC has a feedback circuit in the PCM that controls the EPC current. If this current indicates a short to ground then engine torque may be reduced to prevent damage to the transmission.

P1747 Pressure Control Solenoid Short Circuit

Remaining faults include a faulty solenoid itself (P1745 and/or P1748), or a faulty connection to the solenoid, P1746.

In all these cases owner action is limited to seeking an autobox specialist, provided that the other checks mentioned at the beginning have already been carried out.

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All diagrams Ford copyright, reproduced by kind permission.

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EricR

 

 

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