E250 Bluetec: Limp Home Mode; P00C1
Thread Starter
Junior Member
Joined: Jul 2011
Posts: 24
Likes: 6
'97 Frankenstein
E250 Bluetec: Limp Home Mode; P00C1
2015 E250 Bluetec with increasingly persistent limp home modes triggered lately. At first it would happen once every few weeks. A key cycle sometimes restores proper running for a while. But one day last week it triggered a dozen limp homes in ten miles of driving. No amount of key cycling had any lasting effect.
It registers a P00C1 code and nothing else. This is "Turbocharger Bypass Valve 'B' Control Circuit Low".
Near as I can tell, this code has something to do with either the wastegate control, or the boost pressure control flap (this flaps redirects exhaust flow away from the small turbine to the large turbine).
Where I'm unclear is this: the actuators for both of these systems are controlled pneumatically. Each actuator is plumbed to a "transducer" (as Mercedes calls it) on one barb, and two other barbs that are connected to a vacuum reservoir and ambient air, respectively. The transducers have no electrical component to them.
So I'm puzzled why the code is "control circuit low", which I read to mean low voltage. Now, if it was low pneumatics, then I would expect every other system that is vacuum operated to be affected too - EGR, coolant pump, etc. But nope, all I ever get is the P00C1 code.
What else could this code be related to? A boost pressure sensor? Also, which system is "Bypass Valve B"? I don't have Xentry, just a Launch Elite 2.0 Creader. So kind of flying blind here.
It registers a P00C1 code and nothing else. This is "Turbocharger Bypass Valve 'B' Control Circuit Low".
Near as I can tell, this code has something to do with either the wastegate control, or the boost pressure control flap (this flaps redirects exhaust flow away from the small turbine to the large turbine).
Where I'm unclear is this: the actuators for both of these systems are controlled pneumatically. Each actuator is plumbed to a "transducer" (as Mercedes calls it) on one barb, and two other barbs that are connected to a vacuum reservoir and ambient air, respectively. The transducers have no electrical component to them.
So I'm puzzled why the code is "control circuit low", which I read to mean low voltage. Now, if it was low pneumatics, then I would expect every other system that is vacuum operated to be affected too - EGR, coolant pump, etc. But nope, all I ever get is the P00C1 code.
What else could this code be related to? A boost pressure sensor? Also, which system is "Bypass Valve B"? I don't have Xentry, just a Launch Elite 2.0 Creader. So kind of flying blind here.
Out Of Control!!
Joined: Apr 2019
Posts: 12,253
Likes: 6,916
From: Silicon Valley
W212 MY'14 M276-3.5NA @75kMi
Run Bidirectional Test
2015 E250 Bluetec with increasingly persistent limp home modes triggered lately. At first it would happen once every few weeks. A key cycle sometimes restores proper running for a while. But one day last week it triggered a dozen limp homes in ten miles of driving. No amount of key cycling had any lasting effect.
It registers a P00C1 code and nothing else. This is "Turbocharger Bypass Valve 'B' Control Circuit Low".
Near as I can tell, this code has something to do with either the wastegate control, or the boost pressure control flap (this flaps redirects exhaust flow away from the small turbine to the large turbine).
Where I'm unclear is this: the actuators for both of these systems are controlled pneumatically. Each actuator is plumbed to a "transducer" (as Mercedes calls it) on one barb, and two other barbs that are connected to a vacuum reservoir and ambient air, respectively. The transducers have no electrical component to them.
So I'm puzzled why the code is "control circuit low", which I read to mean low voltage. Now, if it was low pneumatics, then I would expect every other system that is vacuum operated to be affected too - EGR, coolant pump, etc. But nope, all I ever get is the P00C1 code.
What else could this code be related to? A boost pressure sensor? Also, which system is "Bypass Valve B"? I don't have Xentry, just a Launch Elite 2.0 Creader.
So kind of flying blind here.
It registers a P00C1 code and nothing else. This is "Turbocharger Bypass Valve 'B' Control Circuit Low".
Near as I can tell, this code has something to do with either the wastegate control, or the boost pressure control flap (this flaps redirects exhaust flow away from the small turbine to the large turbine).
Where I'm unclear is this: the actuators for both of these systems are controlled pneumatically. Each actuator is plumbed to a "transducer" (as Mercedes calls it) on one barb, and two other barbs that are connected to a vacuum reservoir and ambient air, respectively. The transducers have no electrical component to them.
So I'm puzzled why the code is "control circuit low", which I read to mean low voltage. Now, if it was low pneumatics, then I would expect every other system that is vacuum operated to be affected too - EGR, coolant pump, etc. But nope, all I ever get is the P00C1 code.
What else could this code be related to? A boost pressure sensor? Also, which system is "Bypass Valve B"? I don't have Xentry, just a Launch Elite 2.0 Creader.
So kind of flying blind here.
These 4-Cyl. diesels are famous to run for ever trouble free. It must be something unusual here.
Normally a "low" fault means a bad positive supply, like a fuse or poor connection to 12V.
Let's not waste time right away....
Go to tge obvious first: like you said if it was simple vacum or power supply more than one item would show fault.
The way it WENT GRADUALLY WORSE sounds more like dome plugged up than something fried up like a one-time fuse.
Use your handy bi-directional Elite scanner to test this item with command: on/off in the ECU menu.
At this stage the only thing important is what item is in at fault. Treat the " low " as a misleading condition.
Test the actuator to find out what is not happening: no voltage or no vacuum?
Hope this helps you focus.
Last edited by CaliBenzDriver; Yesterday at 02:59 PM.
Thread Starter
Junior Member
Joined: Jul 2011
Posts: 24
Likes: 6
'97 Frankenstein
I take it back, there is a 12V connection on the transducers. It’s impossible to see it with the transducer in the car.
Okay so these things are electropnematic devices which probably means one of them is getting dodgy.
I’d still love to know which one is “Bypass B” circuit. The wastegate transducer is relatively accessible but the other one is a real PITA to access.
Okay so these things are electropnematic devices which probably means one of them is getting dodgy.
I’d still love to know which one is “Bypass B” circuit. The wastegate transducer is relatively accessible but the other one is a real PITA to access.
Out Of Control!!
Joined: Apr 2019
Posts: 12,253
Likes: 6,916
From: Silicon Valley
W212 MY'14 M276-3.5NA @75kMi
I take it back, there is a 12V connection on the transducers. It’s impossible to see it with the transducer in the car.
Okay so these things are electropnematic devices which probably means one of them is getting dodgy.
I’d still love to know which one is “Bypass B” circuit. The wastegate transducer is relatively accessible but the other one is a real PITA to access.
Okay so these things are electropnematic devices which probably means one of them is getting dodgy.
I’d still love to know which one is “Bypass B” circuit. The wastegate transducer is relatively accessible but the other one is a real PITA to access.
Trace where it's hot near engine rear by the firewall.
I dont know where/what's an E250 BypassB ?
Last edited by CaliBenzDriver; Yesterday at 05:18 PM.
