THE BOSCH EDC15M L SERIES INJECTION SYSTEM (post 1999 models)

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Contents:

  1. ENGINE SENSORS
  2. EXHAUST GAS RECIRCULATION (EGR)
  3. LIMP HOME MODE - THE THROTTLE POSITION SENSOR
  4. MIL LIGHT - the engine management warning light
  5. DIY TPS

INTRODUCTION.

The post 1999 L series powered Rovers and MGs feature Bosch's widely used EDC15M diesel injection system. Also found in VAG and GM/Vauxhalls to mention but two.

The injection pump is a VP30 - this is an axial piston injection pump. (Not a radial VP44 pump)

This single piston pump operates at a higher pressure than the VP37 pump - up to 1400bar (20,500psi) and has its own built-in PSG5 ecu.

This communicates with the main ecu via the can bus (Controller Area Network). The pump ecu needs only to be told how much fuel to inject. It does all the rest, calculating the start & end of the injection and compensating for fuel temperature etc.

The 6 hole injectors operate with a two stage injection to reduce noise and improve emissions.

Unlike the VP37 pump, in this pump, the injected quantity is varied by altering the duration that fuel is supplied. A high speed solenoid valve releases the pressure and as soon as this drops below the injector opening pressure, the injection is terminated. A rotating disc distributes the fuel to each injector in turn. This pump is also rated at 25kw / cylinder (134bhp from 4 cylinders) though this is probably a conservative rating.

1) ENGINE SENSORS

TPS - THROTTLE POSITION SENSOR

The TPS has two signal outputs: one is the pedal position signal, which varies from about 0.5volts pedal up to 3volts pedal down. The other is the pedal up or idle mode switch. This changes from 3.5v to zero as soon as the pedal is moved, thus informing the ecu to switch from idle to drive mode. If this fails you will experience Limp Home Mode - see below for more details.

 IAT - INTAKE AIR TEMP SENSOR.

Fitted either to the left hand end of the inlet manifold (sd/sdis) , or built-in to the MAF sensor. It enables the ecu to correct the fuel quantity injected for different air temperatures. Cooler air = more fuel. the resistance falls with temperature rise (NTC) so the voltage on pin 1 of the MAF plug drops. At 7.5C my 45 reads 3.9k ohms. The ecu also adjusts the timing based on the temperature - advancing it slightly as the temp drops.

CKP - CRANKSHAFT POSITION SENSOR. Tells the ecu when TDC is reached, measures the crank angle and also is used to provide the engine rpm.

MAP - MANIFOLD ABSOLUTE PRESSURE SENSOR.

Fitted to the bulkhead, it is supplied with pressurised air from the compressor outlet. It is used mainly to indicate an overboost condition, which causes the ecu to cut the fuel to reduce the boost to a safe level. On the sdi engine it is also influences the fuel quantity injected. A boost pressure of over 20psi will normally cause the ecu to cut the fuel.

MAF - MASS AIRFLOW SENSOR

This converts airflow into a voltage by relying upon the cooling effect of air passing over a heated sensor. As the airflow increases, the sensor cools down, the heater current is then increased to maintain the temperature constant. This increase in current is converted into a voltage proportional to the airflow. Used to regulate exhaust gas recirculation, and on the EDC15M engines also heavily influences fuel quantity injected.

ECT - ENGINE COOLANT TEMPERATURE SENSOR. (2400ohms at 17C dropping to 300 at about 85C)

Fitted to the outlet elbow at the front left hand end of the engine, it is used by the ecu to control cold start enrichment and heater plug on-time. (Its the upper, 2 wire one, the lower single wire one is for the temp gauge)

FUEL TEMPERATURE SENSOR

This is built into the fuel pump and compensates for the change in fuel density due to temperature. On the sdis, the fuel temp signal is transmitted to the ecu. So could be 'altered' to fool the ecu into injecting more fuel... 

NEEDLE LIFT SENSOR

This is built in to no.1 injector and indicates to the ecu exactly when injection has commenced by providing a pulse when the injector opens. If it is missing due to a fault or short circuit, the engine runs unevenly and may be down on power.

VEHICLE SPEED SENSOR

Fitted to the differential housing near the nearside inboard CV joint, this produces pulses proportional to the speed of the road wheels. The sensor in my 45 produces 10,000 12volts pulses per mile. The signal is fed to the odo and speedo, AND to the ecu. The ecu doesn't return fully to idle mode until the vehicle stops.

BRAKE PEDAL SENSOR.

This just senses the change in voltage from zero to vbat when the brake pedal is pressed. It is used to implement over-run fuel cut off control.

On the sdis, if the switch is faulty, maladjusted or the brake light bulbs are blown, a loss of power may be experienced. This is because the ecu thinks the brakes have been applied, and if the throttle pedal is also pressed, it gets totally confused, goes into a sulk, and cuts the fuel and can turn on the MIL light temporarily! (The programmer had obviously never heard of heel and toeing!)

Faulty sensors - please read this.


2) EXHAUST GAS RECIRCULATION SYSTEM. (EGR)

The egr valve is shown opposite. It is a water cooled tube with a valve in it, connecting the exhaust manifold to the inlet manifold. (Not water cooled on pre1999 engines)

The egr actuator (the circular capsule with the black 3mm pipe attached) is controlled by a solenoid valve fitted to the bulkhead and connected to the brake servo line.

This is pulsed 50times per second by the ecu, with the 'on time' being varied to modulate the volume of exhaust gas fed into the inlet manifold. To calculate how much exhaust gas is being recirculated, the ecu monitors the MAF sensor and notes by how much the signal drops when it opens the valve. (Exhaust gas replacing the intake air causes the drop in MAF signal) This is the only reason for the pre 1999 engines having a MAF!

The ecu keeps the egr valve closed under acceleration, (or boost pressure would escape through the valve into the exhaust manifold) so theoretically there should be no need to disconnect or blank it off. However, there is no harm in disconnecting the small bore pipe to see if it makes a difference.

The solenoid valve buzzes when working - this is normal, though sometimes the EGR valve itself makes a metallic rattling / tinkling noise due to it chattering on its seat when partially open, This can be irritating - if so just try disconnect the pipe.

Bosch claims that up to 40% recirculated exhaust gas reduces emissions, improves fuel economy and minimises soot production. 


3) LIMP HOME MODE (Diesels) WITH REVS FIXED AT ABOUT 1300.

NB Any limp home / reduced power mode can be reset by simply switching the ignition off and on assuming the fault is not still present.

BUT on the post '99 cars, the MIL may stay  on until it is reset via the diagnostic port even though the ecu returns to normal operation. In other words, just because the light is on does NOT automatically mean power has been reduced. (see below)

THE SAGA OF THE THROTTLE POSITION SENSOR. (FAILURE OF THESE IS NOT UNCOMMON ON OLDER CARS)

Recently, the throttle position sensor failed whilst I was on holiday in Argyll. This is one sensor that almost always will cause limp home mode to be invoked. This is understandable, as an erratic throttle signal could lead to an accident if for example, the car was to suddenly accelerate.

Limp home mode is characterised by complete absence of response to accelerator pedal movement, and the engine revs being fixed at about 1300. The car is driveable and you can go up through the gears as the ecu will endeavour to maintain the rpm at 1250 regardless of gear or gradient: max speed is therefore, about 35mph.

The way in which limp home mode occurs can indicate which part of the TPS is faulty.

If the revs rise quickly to 1300 the instant the engine is started, it seems to be the TPS idle switch that is faulty. On the other hand, if the revs build up slowly to 1300, it is he pedal position signal that is absent or out of range or the voltage hasn't started to increase soon enough as the pedal is pressed.

Another indication that the switch signal is wrong or the TPS is maladjusted is that the car can be driven normally so long as the pedal is never fully released, eg you can drive for miles on the motorway. Then once the pedal is released limp home occurs (sooner or later).

TESTING THE TPS.

The sensor has a 4 pin connector nearby with the following wire colours: Stick a pin through the insulation or push the meter probe through the seal and down the wire entry.

PINK/BLACK = 0VOLTS (battery -VE)

RED/GREY = +5Volts from ecu

GREEN/RED =  PEDAL SWITCH - IDLE POSITION: Must be about 3.5volts with the pedal up and as soon as the pedal is moved more than a mm or two, it drops to zero (or below 0.5volt).   If the pedal moves more than this before the switch operates, limp mode will usually occur.

ORANGE/YELLOW  = PEDAL POSITION. Should be about 0.4 to 0.5 volts pedal up increasing smoothly as the pedal is moved to about 3volts on full throttle.

ADJUSTING THE TPS.

1) Make sure that with the pedal released, there is enough slack in the cable to allow the quadrant to abut the end stop on the TPS bracket.

2) Measure the voltages on the wires and confirm they are as listed above.

3) If not, bend the end stop(s) either way until they are correct.

WHY A NEW TPS MAY NOT APPEAR TO CURE THE FAULT?

If the TPS is not adjusted correctly, the ecu will regard it as faulty and limp mode will occur. The most probably causes are:

a) End bracket allows the pedal to move up too much so the position signal is too low. This also means that the position signal will vary significantly BEFORE the switch signal changes.

b) End bracket bent (or cable too tight) so the pedal is not high enough and switch signal REMAINS at zero. (can also give high idle speed)

TPS PART NO:BOSCH 0281 002 370

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4) MIL LIGHT HINTS (Malfunction Indicator Light - Orange engine management warning light with engine symbol on it)

On the pre 1999 cars, the MIL light only comes on whilst a fault is present.

On the later cars, once lit it often stays on until reset via the diagnostic socket. BUT PLEASE NOTE.....

THIS DOES NOT MEAN THE FAULT IS STILL PRESENT OR THAT A REDUCED POWER MODE HAS BEEN IMPLEMENTED.

By watching it when first turning on the ignition, you may be able to tell whether there is still a fault, or it simply needs resetting due to a previous fault.

If the light comes on & stays on, the ecu has detected a fault during its power-on self tests.

If it comes on for a few seconds whilst doing its self tests, and then goes off for about half a second and then comes on again, there is probably no fault present now..

RESETTING THE MIL.

On the 200/400/600 it is reset when the ignition is turned off. If it comes on again, the fault is still present.

On the later models with EDC15M and probably the ZT/75 as well, the MIL may stay on whether or not the fault is still present.

YOU DO NOT NEED TO VISIT A MG-ROVER DEALER AND PAY 50 - 70 to have it reset.

Any autoelectric or diesel diagnostic centre should be able to reset it for about 20. I use a local Krypton agent. Their generic handheld tool will list & clear the DTCs and turn off the MIL, though I did have to tell the technician that it was EDC15 - I don't think it specifically listed a Rover 45 TD. A Sykes Pickavant ACR2 or 4 code reader with Rover 3 or 4 pods will also work.

ALSO SEE THE EOBD PAGES FOR FAULT CODE INFO

5) My Diy Throttle Position Sensor.

A replacement TPS was a shock at 128 + vat & carriage. This was [typically] still cheaper than Rover - they quoted me 148.27+vat, had none and one dealer couldn't even be bothered to phone me back with availability & that's after I told them the Rover part number which they couldn't even find.

Because Bosch had no TPSs in the UK & there was a delay of a week in having one shipped from Germany, I decided to have a go at making a temporary one. This was more of a challenge than I expected - mainly due the ecu being very 'fussy' about the synchronisation of the switch & pedal position signals.

Nor was using a conventional potentiometer straightforward as the throttle quadrant only turns through 90o

The pot was fitted in the original TPS housing and an amplifier constructed to compensate for the pot only turning through a third of its range, yet has to provide a varying voltage from .5 to 3 volts from a 5v supply. A microswitch was also needed to emulate the switch in the TPS - it has to close when the quadrant turns less than 10degrees. Also, I suspect the original pot does not have a linear law, which affects the pedal response.

However I did manage to keep mobile even though it would revert to limp home mode occasionally - usually when slowing down - ie foot off.

THE NEW TPS. Bosch part no 0 281 002 370.

I purchased this through Teeside Autotech - whom I'd order Bosch Yellow books from online last year and received excellent service.

I wondered whether the ecu would need to recalibrate the new TPS. I thought maybe it had to be programmed with the idle & full throttle settings by using a diagnostic mode via the obd connector. So I emailed a Bosch diesel parts stockist, after finding their details on the Boschautoparts.co.uk web site.

So its many thanks to the staff at Andrew Watt of Wishaw, Lanarkshire who passed my email on to Bosch, and to the chap from Bosch UK for phoning me back.

Happily, the answer was - no - the TPS just needs to be adjusted correctly.

The quadrant must be fitted so that the voltage with it against the idle end stop is below .54 volts.

IT WORKED FIRST TIME.

The new TPS arrived a day late thanks to ANC Cumbernauld. I fitted it to the bracket and attached the cable quadrant, but with only the left hand (front) bolt holding the TPS to the bracket. (Allows it to pivot toward or away from the idle end stop.)

This was so I could fit the quadrant by trial and error without having to 'fight' the very strong spring built-in to the TPS housing. Then by swinging it into position, so the peg butts up against the end stop, the voltage was adjusted to about 0.5volts by moving the quadrant on its splines. I checked that the switch also closed within about 10degrees - which is needed to avoid limp home mode and then fitted the 2nd bolt.

I returned the assembly to the car & plugged it in and with some trepidation started her up and went for a spin. Idle speed was correct and the over-run fuel cut off was working as it should again, and no more sudden limp home modes! I also checked the throttle range using eobd and OBD Logger, confirming that pedal up was 0% and pedal hard down was 99.22% - near enough 100% for me!

Back to normal. Today, (16/9/04) has been an average days driving of 130miles from city centres to motorways and has shown up no further problems.

Sat 18th Sept, refitted the cruise control lever, and reattached the cable, after having no further problems.

19th October. I'm pleased to say that I'd had no more problems since replacing the TPS until I changed the car in October for a 03/53 Impression S 115 TD.

The upper photo shows my diy TPS, comprising the butchered housing, a conductive plastic potentiometer, V3 microswitch and assorted bits and pieces - and yes, that's a rubber band you can see. Later replaced with a long spring when it snapped...!

The lower photo shows the new TPS. The variable resistor & switch occupies just the bottom 1.5cm. The remainder contains the 2 torsion springs that control the entire pedal feel & tension, plus bearings.

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