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Fault: ABS BAS ESP warning lights stay lit when car started. Steering is harder than normal. Brake feels normal.
iCarSoft MB 2.0 scanner 38 pin connector
left front speed sensor implausible does not match engine speed
left front speed sensor open circuit
Transmission module and esp module. No other relevant codes. Clear codes and they return.
Action: Replaced left front speed sensor and wire. Corrosion metal debris present on old sensor. Cleaned ABS commutator/geared ring as best as can, scraped each tooth and flushed and blown out with high press air.
Results:ABS BAS ESP lights were out for several drives, but came on again and are now intermittant. Restart car several times without driving and lights go out. They are present on start up before driving after car has been shut down when lights are not present.
Error codes reappear: left front speed sensor/wire
The ABS BAS ESP system seems to be detecting a fault without moving car, ie. wheel speed at 0. Fault can go away and stay off for extended periods.
Would replacing front left axle make sense? The current speed sensor ring is corroded, but intact. It has been in service in Minnesota for its life. Has anyone replaced the speed sensor ring for similar faults?
Bonus round: Why is the steering stiff when warning lights are on.
Replacing the axle is a pain, just got done rebuilding entire front suspension about 5,000 miles ago, and going back in to replace axle is doable but gonna hurt. At least it's warm out.
Does this intermittent error behavior point to the speed sensor toothed ring? If there is a bad spot would it explain this behavior? Will this show up with a live data capture?
Has anyone had to replace an axle because of bad speed sensor ring? Is the engine speed sensor an alternative explanation?
The ABS ESP BSA lights do not come on if a start takes place and they go out. Can drive without them coming on. If a start takes place and they remain illuminated, they stay on, until a start occurs where they go off. A lovely intermittent problem.
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Thanks Dave, it's a chore keeping things protected from the salt here. Staying off the roads as much as possible during sledding season helps.
Wondering what signal is tripping the ABS ESP BAS lights when the car has not moved. Whatever it is, it can go away on its own and no lights come on when started again. Could the speed sensor ring be off sufficiently that where it lands on shutdown could influence the start up and error trigger? Is it a random process that depends on position of sensor ring when car is shut down? A bad spot on ring which may or not be under the sensor on start up and thus does or not trigger warning lights ?
It is an interesting problem, makes one think of all the engineering hours that must have gone into these systems. Given the extreme service requirements, it's impressive they work as intended.
The ring looks to be integral to the axle, but either way with the reasonable price for rebuilt axles with rings installed, a new axle is in order.
What is frustrating is the nature of the issue. This morning went out to start, lights stayed on, the brain decided system was not right. Stopped after a 1 mile drive, return to car and started up with no errors. Pulled into driveway, turned off and restarted no warning lights. If I go out this afternoon to drive, I will bet the warning lights will stay on after start.
Curious as to what is being sensed when car is started that triggers the warning lights to stay on. Is it a historic error that hasn't been properly cleared? Not likely as it can go into normal state without lights on.
Is there a technical source that describes signal inputs and behavior of the system, it would be a good read.
Walked around the car with the new axle cradled in my arms, whispering quietly to the myself. When I rethought the error messages and a possible explanation that did not involve the sensor ring itself.
How does the system know to throw error code when it isn't even driven? Ah ha, bias voltage. Bias voltage is applied to the wiring and the expected voltage is sensed instantly, as soon as key is turned. If return voltage is off, system trips error. This fit with the intermittent signal, sometimes on, sometimes off, even without use of system ie. no drive. Explains the speed sensor wire error messages. Renewed efforts to test for wiring failure.
There is a youtube video for W163 owners showing how to disconnect the module, clean with spray, and reconnect. I had removed all the modules when I changed the upper control arms and recalled that it was a lot of connectors etc.
Could it be possible that contamination had entered a connector socket and was giving intermittent connection? Well, disconnected module and sprayed CRC cleaner into the connections and plugged back in.
None of the lights have been on since.
Still not sure why steering was stiffer when the lights were lit?
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