steering angle sensor strange issue

HI guys,

I have a bit of a puzzle on my hands. I have an ABS code that illuminates 2 of the 3 ABS lights on the dash. Icarsoft MBII told me it was an implausible signal/reading from steering angle sensor. I used the same tool to read the sensor values and come to find it was reading perfectly one way (left) 0 degrees to bottom out at -6xx degrees. If I turn right however, it will not read past 80 degrees. After that the readings are ---, or no reading, and then reads on again past 680 degrees (almost full right turn). I thought I had a bad sensor on my hand and got another one. Only to find the exact same result. Of course I recalibrated with the same tool every time I swapped. The readings when available are incredibly precise. It reads at 75, 76, 77,78,79 and 80 degrees and any turn to the right after that is met with the ---, or no reading....
Has anyone come accross that issue? I doubt I have 2 bad sensors with same default. Where do the sensor sends its info to? ABS module I'm guessing. I hope that's not fried somehow....

Any suggestions? It is a 2006 T1N Sprinter 2500.

Thanks!

Killer.
Most problems on Sprinters are caused by faulty electrical connections. You do not say which model you have but if you get a can of contact cleaner and clean the plugs on the loom between the steering and the ECU you probably will fix it. Eric.

Eric Experience said:

Killer.
Most problems on Sprinters are caused by faulty electrical connections. You do not say which model you have but if you get a can of contact cleaner and clean the plugs on the loom between the steering and the ECU you probably will fix it. Eric.

Click to expand...

DAAAAHHHH!!! 2006 Sprinter 2500 T1N

I will try that. Something is telling me the problem is somewhere else if the wires or connections were bad I don't think i'd read much at all. Again, it is so precise in the range it reads value from. Since I'm guessing wiring goes to the ABS module, is that on the ABS pump in engine bay?
Thanks for your input Eric.

I have 2 more tests I want to run but I think alignment might be a problem. I'm curious to see what I read from a working sprinter as far as steering angle with the tool. I have another one I will be able to compare to.

In the car is the can bus connected to the ground somehow? When I was testing the wires from the sensor connector to the abs module I noticed the 2 green wires, which I believe to be can bus +and - show 1020 ohms to the ground. Normal?

The CANbus is probably a "balanced" circuit ... the receivers look at the difference between the two wires, without really referencing "ground". This isolates the communications from whatever hiccups the car's primary electrical system may be doing (such as 10v during starting to 14.4v during charging).

At some point in the circuitry there will be a resistor network holding the wires at some "neutral" point, just to give induced currents a place to go (see quoted section below). The two wires themselves are twisted together as further shielding against induced currents from other heavy-current (or spikey) wires in the bundles.

To read/see the CANbus with a scope or logic analyzer, you need to run it as a "differential" input (one wire to channel A, the other to channel B, then set the scope to "A-B"). If your scope is not in any way connected to the vehicle's frame, you could, instead, connect one of the CANbus lines to the scope's "ground".

As an example of what the 1020 ohms is used for, here's a quote from the 2006 service manual about the TCM's use of the CANbus C pair:

CAN C Bus Indirect Input Signals
A 2.5-volt bias (operating voltage) is present on the CAN C bus any time the ignition switch is in the RUN position. Both the TCM and the ABS apply this bias. On this vehicle, the CAN C bus is used for module data exchange only

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(from page 8e-8) ... and that says that two modules are both (redundantly) providing that bias voltage. If one were to fail, the other would keep the CANbus at its designed bias (allowing +/- 2.5v (or 5v peak-to-peak) signals to continue to pass).

--dick

Thanks autostaretx
I like nerd stuff but that's a lot to absorb! I think the wires are fine. I'm going to get an alignment done and see if the code goes away after alignment and angle sensor reset. Otherwise I will get another Sprinter and read with the same tool the angle since I know it works. It is possible the tool is not able to translate some of the signal since I think the option is for 90x.6 vans which this on eisn't if I'm not mistaken. So it's possible the read on the other VAN will yield the exact same readings.....

As i recall, the DAD (actually an old (v2.3) CarSoft multiplexer imported from Europe) didn't care about series/body (211,315,906,etc)
The model designation can be read from set into the ESP module.

It only needed to be told "diesel" or "petrol", and then (for engine stuff) CDI2 (OM612) or CDI3 (OM647).


The steering angle display is provided as a part of the ESP/Traction screen:
(this is from my 2005 Sprinter)



And the model designation is one of the parameters you can set into the ESP:



(i don't know if it got the "901" from my 118" wheelbase Sprinter, or if it's just a DAD prompting ... the Wheelbase default of "middle" certainly ain't me.)

The service manual only says "calibrate steering angle sensor using the scan tool" (2006, page 5-33)

--dick

Doing more reading (in the Chassis diagnostic manual)...
among other things, they say that steering angle issues need to be corrected before addressing other error codes.
(you probably knew that, i'm just plodding through the documentation)

The Drive Test tree (page 29) says:

NOTE: When the vehicle is in a turn, the ESP compares the Steering Angle
Sensor value and the speed of the inner and outer wheels to determine if the values are plausible.
Inspect the front end and steering components for damage or misalignment.
Inspect the Lateral Acceleration Sensor for correct mounting and installation.
Inspect the tires and wheels to make sure that they are the correct size. All tires must be the same size

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So the "implausible" can arise if the wheel speed sensors don't agree with the "measured" angle.
Certainly a not-almost-zero-angle-when-going-straight would fit that criterion.

You said that you did run through the calibration routines, so it is a puzzle.

On page 66, they discuss problems if the sensor reports more than 720 degrees:

NOTE: If a system undervoltage or overvoltage DTC is set along with this DTC, diagnose the system voltage DTC first.
NOTE: Electromagnetic (radio) interference can cause an intermittent system malfunction by interrupting communication between the sensor and the CAB.
NOTE: The Steering Angle Sensor is very sensitive to changes due to alignment problems. The sensor must be recalculated using the DRBIIIt if alignment has been changed by more than 5 degrees.
---------
Inspect the related harness and connectors.
Look for any chafed, pierced, pinched, or partially broken wires.
Look for broken, bent, pushed out, or corroded terminals.

Click to expand...

--dick
p.s. 2006 Chassis manual: http://www.diysprinter.co.uk/reference/2006-VA-Chassis.pdf
The 2004 is at http://www.diysprinter.co.uk/reference/ , too.

A bit off topic.

autostaretx said:

Doing more reading (in the Chassis diagnostic manual)...
...

Click to expand...

Once someone gets you on the scent you are like a combination of Bloodhound and Pit Bull.

I intend that in the kindest way possible. It is an admirable trait for helping others here on the forum.

vic