ABC multiple faults (looks like a CAN short)
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2005 CL65
ABC multiple faults
Guys,
Car: CL65, 60K, 2005
ABC: replaced all hydraulic components
1) Every hydraulic hose
2) Pump
3) Both valve blocks, all accumulators
4) Front struts
5) Rear struts were replaced 20K miles ago
Car drives very well, no sags, excellent handling, etc.
But, under hard acceleration from rest, get a red ABC fault. Driving the car hard on twisty's and fast highways, mountain roads, etc NO fault.
Can't reproduce problem in reverse.
Can also reproduce by holding the car with the brakes in D. Hit 1.9K revs and DING fault triggered. Easier to trigger fault on hard left turn at speed. Hard right turn, no fault. Hard left or hard right in reverse, no fault.
Very predictable fault. Never fires intermittently, only under specific conditions described above.
STAR reports all sensors have failed. Switching off and on resets the problem.
DAS states that if multiple sensor faults are reported, then it's a short in the harness or in the sensor.
Replaced all the sensors. 4 Level sensors, 3 acceleration sensors, lateral and long sensors, everything on the fault list except the pressure sensor. Swapped out controller. All tests and diagnostics pass.
All connectors look good.
When the fault is triggered, it looks like a CAN bus short to ground. Every sensor goes to zero, pressure sensor goes to max.
Any ideas ?
Car: CL65, 60K, 2005
ABC: replaced all hydraulic components
1) Every hydraulic hose
2) Pump
3) Both valve blocks, all accumulators
4) Front struts
5) Rear struts were replaced 20K miles ago
Car drives very well, no sags, excellent handling, etc.
But, under hard acceleration from rest, get a red ABC fault. Driving the car hard on twisty's and fast highways, mountain roads, etc NO fault.
Can't reproduce problem in reverse.
Can also reproduce by holding the car with the brakes in D. Hit 1.9K revs and DING fault triggered. Easier to trigger fault on hard left turn at speed. Hard right turn, no fault. Hard left or hard right in reverse, no fault.
Very predictable fault. Never fires intermittently, only under specific conditions described above.
STAR reports all sensors have failed. Switching off and on resets the problem.
DAS states that if multiple sensor faults are reported, then it's a short in the harness or in the sensor.
Replaced all the sensors. 4 Level sensors, 3 acceleration sensors, lateral and long sensors, everything on the fault list except the pressure sensor. Swapped out controller. All tests and diagnostics pass.
All connectors look good.
When the fault is triggered, it looks like a CAN bus short to ground. Every sensor goes to zero, pressure sensor goes to max.
Any ideas ?
Last edited by Shiv Sikand; Jul 27, 2017 at 09:13 PM.
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Joined: Apr 2011
Posts: 130
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From: NC
'15 GLK350, '05 CL65 AMG, '04 C320 4matic
On a CAN bus a short will shut down all communications over the bus. It could be an open on a branch of the bus. You should be able to measure a resistance between the two bus wires, at any node on the bus, of about 60ohms. Significantly different readings indicate a problem. In that case look for a loose or corroded connection at a junction that is common to the components giving errors.
Last edited by Geraldius; Jun 13, 2017 at 11:16 PM.
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Joined: Apr 2011
Posts: 130
Likes: 53
From: NC
'15 GLK350, '05 CL65 AMG, '04 C320 4matic
A CAN controller will typically shut off communication to an unresponsive device on the bus after some number of failed retries. So even if the malfunction ceases the device might not be picked back up by the controller until commanded to do so by software, or by a reset of the hardware.
My guess is that flexing in the wire harness at a connection is momentarily causing an open, or high enough resistance to let the bus become electrically noisy.
Holding the brakes while in drive while revving the engine, or hard acceleration, will both cause the engine to torque in one direction. Reversing will cause it to torque in the opposite direction.
Bad motor mount on one side? Have a helper watch the engine for abnormal movement while doing your power braking test. (don't run anyone over)
My guess is that flexing in the wire harness at a connection is momentarily causing an open, or high enough resistance to let the bus become electrically noisy.
Holding the brakes while in drive while revving the engine, or hard acceleration, will both cause the engine to torque in one direction. Reversing will cause it to torque in the opposite direction.
Bad motor mount on one side? Have a helper watch the engine for abnormal movement while doing your power braking test. (don't run anyone over)
Last edited by Geraldius; Jun 13, 2017 at 11:49 PM.
Thread Starter
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2005 CL65
If I watch the actual values very closely on DAS, the moment there is a large forward physical impulse, I see the actual sensor voltages for the components on the list go to zero virtually instantly and the fault light comes on.
I have thought about your hypothesis previously, but I don't know how to isolate it.
A loose or a corroded connector is a valuable thought but there are no obvious connectors beyond the sensors themselves and the harness for these connectors is all 9ver the car. The lat and long sensors are in the footwells for example, the rear acc sensor is under the parcel shelf etc.
I have thought about your hypothesis previously, but I don't know how to isolate it.
A loose or a corroded connector is a valuable thought but there are no obvious connectors beyond the sensors themselves and the harness for these connectors is all 9ver the car. The lat and long sensors are in the footwells for example, the rear acc sensor is under the parcel shelf etc.
Last edited by Shiv Sikand; Jun 13, 2017 at 11:55 PM.
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Posts: 681
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Benz
If I watch the actual values very closely on DAS, the moment there is a large forward physical impulse, I see the actual sensor voltages for the components on the list go to zero virtually instantly and the fault light comes on.
I have thought about your hypothesis previously, but I don't know how to isolate it.
A loose or a corroded connector is a valuable thought but there are no obvious connectors beyond the sensors themselves and the harness for these connectors is all 9ver the car. The lat and long sensors are in the footwells for example, the rear acc sensor is under the parcel shelf etc.
I have thought about your hypothesis previously, but I don't know how to isolate it.
A loose or a corroded connector is a valuable thought but there are no obvious connectors beyond the sensors themselves and the harness for these connectors is all 9ver the car. The lat and long sensors are in the footwells for example, the rear acc sensor is under the parcel shelf etc.
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Benz
Like the above guy said check for corrosion. Then what I would do is get a multimeter and back probe the power and ground to the control module. See if you are briefly loosing voltage when the fault occurs.
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Joined: Jan 2017
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2005 CL65
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Cl65 AMG
Having worked in the Tune-up & driveability department for G.M. for a long time, I would get cars like this where doing what you described would get the car to act up I would hold the scanner under the hood and grab the engine wiring harness and move it around hoping to see a reaction. I would go that
way trying to isolate areas that might react to engine movement. I wish you good luck !!!!
way trying to isolate areas that might react to engine movement. I wish you good luck !!!!
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2005 CL65
Hi Folks,
Thank you to everybody for their responses so far.
I have now analyzed the circuit diagrams and the pins. I have attached the image for your review. The problem is not CAN related, because these are all analog 3 wire sensors.
My next step now is to physically remove the power pin for each sensor, sequentially, from the control unit connector (power and ground are common for all sensors, but each has a separate pin thank heavens - except for the left and right front body acceleration sensors, and the longitudinal and lateral acc sensors which are shared via z splices) and then stimulate the fault. This will allow me to isolate the wire segment that is causing the problem.
Cheers,
Shiv
Thank you to everybody for their responses so far.
I have now analyzed the circuit diagrams and the pins. I have attached the image for your review. The problem is not CAN related, because these are all analog 3 wire sensors.
My next step now is to physically remove the power pin for each sensor, sequentially, from the control unit connector (power and ground are common for all sensors, but each has a separate pin thank heavens - except for the left and right front body acceleration sensors, and the longitudinal and lateral acc sensors which are shared via z splices) and then stimulate the fault. This will allow me to isolate the wire segment that is causing the problem.
Cheers,
Shiv
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2005 CL65
Resolved
ABC problem is black/yellow power circuit wire of right front level sensor is being crushed between the air filter housing and the right front strut tower. There is a sharp surface on the tower that cut through the wire.
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Benz
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2005 CL65
The bulging section is where we added a lot of rubber to prevent it happening again. Also, the engine mounts were replaced, so the air box is a lot higher in this pic than it used to be, so perhaps that was the root cause of the rubbing.
Geraldius called it !
Geraldius called it !
Last edited by Shiv Sikand; Oct 17, 2017 at 02:16 AM.
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Joined: Nov 2021
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2003 s55 amg
Thank you!
had this same issue with my s55 and it was bugging me out. Couldn’t find the source, until I stumbled upon this thread. I had the same exact codes you did. Something seemed very off because it was only giving sensor codes. Turns out my wiring harness on the FR passenger side strut mount was cut into by my custom intake system. Luckily the wires weren’t in bad shape, other plastic sheath was torn but wire intact. Put electrical tape on it and it worked like a charm! Pm me would love to send you something as appreciation! Lol
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Moe
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Joined: Jan 2017
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2005 CL65
had this same issue with my s55 and it was bugging me out. Couldn’t find the source, until I stumbled upon this thread. I had the same exact codes you did. Something seemed very off because it was only giving sensor codes. Turns out my wiring harness on the FR passenger side strut mount was cut into by my custom intake system. Luckily the wires weren’t in bad shape, other plastic sheath was torn but wire intact. Put electrical tape on it and it worked like a charm! Pm me would love to send you something as appreciation! Lol
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Moe
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Moe
