Guys, not been on here for a while as (at last) the IT infrastructure business is booming again so spare time is a distant memory.
My E280CDi (2006 and just under 100k miles) switched on the check engine light & dropped into limp mode on Friday and so as I "limped" home I called out Mobilo for diagnosis.
Code was 2501-001 which indicates a turbo positioner (component Y77/1) signal fault. Star was used to exercise the positioner a few times - this test passed.
This car has a Garrett turbo which has an electrical (screw-drive) positioner that sets the variable-vane angle inside the exhaust side of the turbo to control boost.
There was no accompanying 2359 code (which would indicate boost too low or too high and often means the variable vanes are stuck or sticky).
Merc dealer contacted as part of the Mobilo process recommended a new turbo as the positioner is integral and not available separately (even though it unbolts from the turbo!). Roughly £1,500 after some discussion on labour...(and no part in stock).
I asked the Mobilo guy to print and then reset the codes so the car was out of limp mode (they have an HP printer in the R-class cars).
Reading the charge pressure control logic, it occurred to me that the fault code actually means that the positioner can't achieve a sensible boost reading and so I decided to have a play before looking for a sensibly-priced replacement turbo (as an aside, the turbo is also fitted to Jeeps and Chrysler models with the same 3ltr V6 engine and also available via Garrett dealers - these routes are 20-35% less than the Merc part but are 100% identical -there is no coding on this part).
First check was to unclip the positioner linkage and check that the variable vane mechanism inside the turbo was moving correctly. It was free and smooth with no stickiness from stop to stop.
So, Star had checked the electrical part of the actuator and I had checked the physical......
I took the air filter pipe off and spun the turbo by hand - smooth and free with no noise.
Next was to check the exhaust back pressure sensor (located to the side of the turbo on the EGR casting).
(this car has no DPF so this is the main exhaust-side sensor and is used by the ECU as one of the parameters to manage the turbo - i.e. to estimate exhaust gas flow).
This was sooted up and the hole in the casting was narrowed with soot as well.
I decided to take out the EGR valve for a look at the same time (2 bolts and a wiggle).
EGR was a bit dirty but amazingly clean by the old standards for a diesel at 100k miles.
I cleaned out the pressure sensor and the hole it reads through using a cloth in the EGR casing to catch the debris (the sensor is a simple diaphragm variable resistor device that feeds a voltage back to the ECU).
All reassembled the car has since not missed a beat (we went to Sheffield and York and back plus lots of local mileage while we were there - over 300 miles total) and is also improved in linearity of low engine speed torque and gearchange smoothness at low throttle inputs.
I had been aware of a very slight power oscillation on very low throttle before the failure so this might well be another diagnostic for this fault. This has also completely gone.
Early days, I know but at least the £1500 (dealer) or £550 (Garrett and DIY) is still in my pocket so far.......
My E280CDi (2006 and just under 100k miles) switched on the check engine light & dropped into limp mode on Friday and so as I "limped" home I called out Mobilo for diagnosis.
Code was 2501-001 which indicates a turbo positioner (component Y77/1) signal fault. Star was used to exercise the positioner a few times - this test passed.
This car has a Garrett turbo which has an electrical (screw-drive) positioner that sets the variable-vane angle inside the exhaust side of the turbo to control boost.
There was no accompanying 2359 code (which would indicate boost too low or too high and often means the variable vanes are stuck or sticky).
Merc dealer contacted as part of the Mobilo process recommended a new turbo as the positioner is integral and not available separately (even though it unbolts from the turbo!). Roughly £1,500 after some discussion on labour...(and no part in stock).
I asked the Mobilo guy to print and then reset the codes so the car was out of limp mode (they have an HP printer in the R-class cars).
Reading the charge pressure control logic, it occurred to me that the fault code actually means that the positioner can't achieve a sensible boost reading and so I decided to have a play before looking for a sensibly-priced replacement turbo (as an aside, the turbo is also fitted to Jeeps and Chrysler models with the same 3ltr V6 engine and also available via Garrett dealers - these routes are 20-35% less than the Merc part but are 100% identical -there is no coding on this part).
First check was to unclip the positioner linkage and check that the variable vane mechanism inside the turbo was moving correctly. It was free and smooth with no stickiness from stop to stop.
So, Star had checked the electrical part of the actuator and I had checked the physical......
I took the air filter pipe off and spun the turbo by hand - smooth and free with no noise.
Next was to check the exhaust back pressure sensor (located to the side of the turbo on the EGR casting).
(this car has no DPF so this is the main exhaust-side sensor and is used by the ECU as one of the parameters to manage the turbo - i.e. to estimate exhaust gas flow).
This was sooted up and the hole in the casting was narrowed with soot as well.
I decided to take out the EGR valve for a look at the same time (2 bolts and a wiggle).
EGR was a bit dirty but amazingly clean by the old standards for a diesel at 100k miles.
I cleaned out the pressure sensor and the hole it reads through using a cloth in the EGR casing to catch the debris (the sensor is a simple diaphragm variable resistor device that feeds a voltage back to the ECU).
All reassembled the car has since not missed a beat (we went to Sheffield and York and back plus lots of local mileage while we were there - over 300 miles total) and is also improved in linearity of low engine speed torque and gearchange smoothness at low throttle inputs.
I had been aware of a very slight power oscillation on very low throttle before the failure so this might well be another diagnostic for this fault. This has also completely gone.
Early days, I know but at least the £1500 (dealer) or £550 (Garrett and DIY) is still in my pocket so far.......
