Vehicle speed sensor

[PSX]

I've been getting an error code for the vehicle speed sensor ('implausible signal' - the car does reach some speeds but I hadn't described them as implausible myself ) for some time now and slightly hesitant acceleration and uneven running has led me to buy a new one so I can try replacing it.

I know it sits ontop of the gearbox - however I just can't seem to see the thing in order to reach it and try to change it myself.. Could anyone provide a photo of the sensor's location or some tips on which parts I'll need to remove to get down there? Car is a LCR225.

Cheers,

Alex

 

[Deleted member 12147]

Had the same problem before christmas and couldn't find a picture anywhere, so to help you i've taken some. It's covered by some silver heat shield material.

 

[PSX]

Many thanks, I was out just now hunting for the thing but rain stopped play! Will give it another shot shortly!

Alex

 

[PSX]

Found it... Cheers for the photos! I had my entire arm down the back of the engine pretty much, slipped the heat-shielding back up along the cable, unplugged the connector, then took my trusty Halfords ratchet with knuckle joint and 9mm socket to free the bolt - enough space for 2 notches of turn and then it was finger tight (thankfully didn't need anymore than this.. dropping the tool would not have been clever!). Definitely a job to be done by feel alone!

Sensor pops out with a little force due to the rubber O-ring securing it, and be aware that it will be coated in gearbox oil!

Car is running much more smoothly now from what I can tell, a lot more precise on fuelling and when letting the clutch out in the lower gears (1st through 4th).


Alex

 

[andycupra]

Found it... Cheers for the photos! I had my entire arm down the back of the engine pretty much, slipped the heat-shielding back up along the cable, unplugged the connector, then took my trusty Halfords ratchet with knuckle joint and 9mm socket to free the bolt - enough space for 2 notches of turn and then it was finger tight (thankfully didn't need anymore than this.. dropping the tool would not have been clever!). Definitely a job to be done by feel alone!

Sensor pops out with a little force due to the rubber O-ring securing it, and be aware that it will be coated in gearbox oil!

Car is running much more smoothly now from what I can tell, a lot more precise on fuelling and when letting the clutch out in the lower gears (1st through 4th).


Alex

so have you fixed it by replacing it or simply removed it?

i cant imagine why the speed sensor would affect fuelling and clutch control... anyone?

 

[PSX]

I replaced with a new part from SERE motors yes, no the sensor doesn't directly affect your clutch or fuelling - but my understanding is the ECU relies upon a consistent vehicle speed reading combined with MAF reading in order to provide a good air/fuel ratio for smooth running - and one of the issues I have been experiencing is an intermittent uneven running at low throttle inputs - specifically when changing gears at high torque (i.e. 1st to 2nd, where any sharp inputs cause a bit of a lurch re-engaging the clutch).

To be more clear - I'm as smooth as I can possibly be when changing gear between the low gears, and was finding it difficult to get slick and smooth changes at times until I swapped this sensor out.

I'm still not 100% certain that the uneven running isnt down to an old MAF (30,000 miles, original Bosch part) or in the case of gearchanges, a dodgy clutch slave cylinder (original part), however the speed sensor is the only part to repeatedly throw an engine management light, so this seemed like a wise idea.. Will report back if the low speed running turns bad again.

Alex

 

[Sly-Delvecchio]

Hi mate,

I'm having trouble with "speed sensors" at the moment.

Have you run VAG-COM to discover the error properly? What did it say?

Do you know if this is the same kind of thing as the Camshaft Speed Sensor or Crankshaft Speed Sensor?

 

[Slimy]

Hi mate,

I'm having trouble with "speed sensors" at the moment.

Have you run VAG-COM to discover the error properly? What did it say?

Do you know if this is the same kind of thing as the Camshaft Speed Sensor or Crankshaft Speed Sensor?

I thought that if the car gets a crank or cam speed sensor it goes into limp home mode, as it normally means a failing or failed cam belt?

The engine speed sensor is less important, but still generates an ECU light.

 

[Sly-Delvecchio]

Done some research & asked some people. The engine speed sensor is the crankshaft speed sensor, aka crankshaft positioning sensor.

I think the "engine speed sensor" can also be the camshaft speed sensor, although quite rare.

No a failed crankshaft sensor won't put the car into limp mode, but it can give some strange problems i.e. car not starting, randomly dropping revs when driving or cutting out and starting again when driving.

On mine (TDI), it also makes the glow plug light flash.