Mercedes Common ECU Failures

email  p@remmington.plus.com

site index A-Z

Vito 110 CDi 2.2D 1999-03 engine code 611.980 that will not rev above 3000rpm, check ECU output pin number 18 to MAF air flow meter, it should be a constant 2V when engine idling, input from pin number 33 harness side should scope out 11V-14V rising with engine revs, falling on deceleration.  If any other values are recorded suspect main ECU module has failed. 

Vito 122 (EDC 15CO) have near to impossible to remove injectors fitted, its rumoured in the trade that Mercedes main dealers just quote customers for a new cylinder head at 2000+ including, the injectors & other parts, due to their high labour charges and the inevitable chance of breaking an injector in its seat.  We have attempted the job three times in our workshop & failed twice to remove a whole set, you have been warned!

SLK (from 1999) C class (from 2002) suffer from 'check engine' light illuminating with PO30/32 codes (misfire). This is caused by defective soldered spur connection in wiring harness (+12V feed to coils). Resolder to rectify.

SLK 320 2000-04 suffer BAS, brake assist problems.  Problem will manifest itself with symptoms including touch start feature not working and complete non start.  Cause due to CAN data bus malfunction.  Multiplug 3 on BAS module likely to have corrosion, if not moisture in BAS module is a common cause.  BAS modules cost the earth.  Repair if possible makes financial sense.

Sprinter Vans all years suffer from wiring problems in the loom behind the battery which damage the ECU, we have seen several of these catch on fire.

S-Class (220) S280 2.8 + S320 3.2  1998-04  Bosch ME 2.1 type.  Suffer voltage output from ECU pin C22 to accelerator pedal position sensor, output voltage should be 5V.

M-Class (163) 2.7D ML270 CDi 1999-05  suffer engine running problems due to air in low pressure fuel system.  Faultcode P1187 maximum pressure exceeded.  Cause being bad design of fuel filter, Mercedes UK sell a modified fuel filter, part number 6110920001

A-Class (168) A160 CDi 1.7D 2001-05  ESP warning light illuminated, faultcode C1142 stored in module.  Problem being G-force sensor too sensitive.  This module can be updated to meet specification of the later up-rated part number 0295454132.

A-Class (168) starter motor replacement on all petrol variants 1.4 - 1.6 - 1.9.  Involves removing engine undertray & dropping the engine on the starter motor side over three inches, to allow access to the starter motor.  Engine removal is not needed as some tech' manuals advise.  Book time is four hours.  Last one I enacted albeit on the floor with a trolley jack, took me a whole day (eight-nine miserable hours).

E320 1991-96 suffer a common fault with the VDO ECU fitted to the E320 and various other models. The problem is with the coil drivers inside the ECU failing thus causing the engine to misfire.  This unit can usually be repaired at very low cost.

Late E320 E280 CDi V6 engines suffer constant limp mode due to intake swirl motor failure.  Code present 2513-001.  We can supply an electronic engineered solution for this at our workshop to get the car out of limp mode with out changing the 1500.00 manifold and motor.  click on this link

ML Vito E-class 270 CDi engines suffer constant limp mode due to intake swirl motor failure.  Code present 2513-001.  We can supply an electronic engineered solution for this at our workshop to get the car out of limp mode with out changing the 1500.00 manifold and motor.  click on this link

Late E-Class W211 & R203  K-line activation & de-activation of the electro-hydraulic brakes.  Laser tools do a handheld electronic tool for 125 ish.  Part Number: 4311 (18-12-07). 

All late Mercedes.  Identifying which engine management system is on your car is important to establishing whether or not we can rebuild ECU. Basically we can rebuild HM type ECUs but not (currently) PMS type ECUs. HM = Hybrid Management System, PMS = Pressure Management System.  PMS type ECUs manufactured by Bosch and Siemens can be identified by two rectangular connectors on top of ECU (opposite metal base plate) and vacuum hose attachment.  HM ECUs manufactured by VDO and Bosch are cast alloy rectangular boxes with top and bottom covers held in place by small anodized torx screws. There are two rectangular connectors on the side of ECU.  VDO ECUs are also fitted to SsangYong Musso and Korando vehicles from 1992. CAUTION: These ECUs are difficult to source for SsangYong as the UK dealer network has closed down.  Failure symptoms for all ECU types are loss of spark on 2 cylinders. On Bosch and Siemens PMS type ECUs, this failure is caused by ECU design - ignition power stage transistors are glued to ECU base plate. This glue joint fails and transistor junctions melt once thermal conductivity is lost. We are now able to rebuild these ECUs.  On VDO and Bosch HM ECUs, the cause of failure is more difficult to ascertain, but the system design and components appear to be under-specified for automotive applications.

Pencil type glowplugs fitted to newer Mercedes diesel engines are prone to snapping off.  Its getting common in the small garage trade, to refuse the job of replacement.  It may pay to pre-warn your customers of the risk & possible extra expense.  Before starting the job!  It is rumoured, main Merc dealers, will not quote for glowplug removal on Vito van diesel engines, because 50% of the time they end up replacing the cylinder head.

Mercedes CDI engines.  Later type diesel injector suffer leakages.  Lack of a thick copper sealing washer results in blow by of combustion gases, this leads to carbon build up (known as 'black death' in the trade) around the injectors which can seize the injectors solid in the head.  One of the first signs of injector leakage is fumes inside the vehicle.  Both issues more common on the Sprinter and Vito than other applications.  Injectors can be removed sometimes by soaking them in thinners, over the course of a few days.  Most-all of the carbon must be removed to get rocker cover off.  It is rumoured, main Merc dealers, will not quote for injector removal on Vito van diesel engines, because 50% of the time they end up replacing the cylinder head.  In E-class Mercs, the dealers just wreck the injectors with a slide hammer and bill the customer for a new 400 ish per injector.  We have a special 1200 puller made in Spain at our workshop to remove these injectors, its a very cost effective answer to this nasty problem.

Mercedes 2.9 diesel engine (Pre CDI).  Superb engine found it's way into the Sprinter and SsangYong Musso , thou  the Sprinter is fitted with the better Bosch VP37 pump.  A good low revving engine which if maintained goes on and on and on.

All Mercedes Models > 2000  Intermittent poor/non start or poor idle/running.  Has vehicle got over-voltage protection relay (also called OVP relay or surge protection relay)? If yes REPLACE! any problems here can cause fuel injection system mis-operation.  We have changed hundreds of these over the years in our workshop.

1980's Mercedes  Bosch ignition ECUs types 0227 100 023 and 0227 100 042 fitted to many 1980's Mercedes models suffer common failure with loss of spark as main symptom.  ECU is a rectangular cast alloy box approx. 10cm deep by 8cm across by 4.5cm high with 3 mounting screws. It has 2 circular connectors (1 pin and 4 pins). Cause of failure appears to be deposits of dissimilar metal corrosion building up on (alloy) base of ECU where it is mounted on steel. This reduces ability of ECU to dissipate heat and leads to premature failure of power transistor and associated components. If you own a classic, preventative maintenance should include cleaning deposits off base and remounting with thermal grease.

2006 spec touchscreen MB STAR loaded with WIS-DIS

 

Page updated 28-05-18

(date information written)