Car serviced now speedo 10mph too fast?

[Pani]

After months of research and reluctance due to fear of poor workmanship, I took my car in for an extensive service.

The shop performed an Inspection 2 (including valve adjustment, tranny and diff fluid flushes). I also requested replacement of the DM-TL module due to a persistent SES light and the transmission shift pin service to be done. The shop was able to replace the DM-TL and reprogrammed the computer for unspecified updates, but they were unfamiliar/hesitant to do the shift pin service, so they sent the tranny out to a specialist.

Anyway, now that I have the car back I've noticed that the speedometer consistently reads 10mph higher than road speed as measured by GPS. Even at low speeds like 25mph, the speedometer reads 35mph. I know our speedometers aren't the most accurate, but this discrepancy seems extreme and I am sure it was not this inaccurate before the service.

Any thoughts on what could be going on?

Thanks,
Pani

[Vintage42]

Maybe a speed sensor is not working right. I think a sensor on the right rear wheel gives speed to the ECU, and a sensor on the differential gives speed to the speedometer. Maybe the one on the differential was disturbed when the gear oil was changed.

[Pani]

Yeah, that's what I was thinking too. I will have the shop check that when I take it back.

They found that my Rogue Engineering RSMs where shot and replaced them with JTD RSMs one of which is squeaking over the slightest bump. Experiences like this make me dread any time I have to service the car. Unfortunately, I'm too busy these days to do any of the work myself.

[Vintage42]

... They found that my Rogue Engineering RSMs where shot and replaced them with JTD RSMs one of which is squeaking over the slightest bump...

I wonder if the Rogues' bumpers were deteriorated or their plates broken. The JTDs look like works of art. I think the noise can come from not using enough of the paper gaskets between the plates and the body; there is a DIY somewhere that mentions that.

[Shoe Coupe]

s54 mcoupes have horribly inaccurate speedos. Its not the sensor, if you hook up a OBD2 scanner, the speed is dead accurate. It is the cluster.

Ive looked into this plenty, there's another thread on here that talks about this.

[Vintage42]

s54 mcoupes have horribly inaccurate speedos. Its not the sensor, if you hook up a OBD2 scanner, the speed is dead accurate. It is the cluster...

You mean the inaccuracy is in the speedometer gauge in the cluster. Is it normal, or a malfunction? If a malfunction, would it show up in the "cluster test"?
Videos:
YouTube "bmw cluster test"
See test 1 and test 8:
http://www.bmw-m.net/TechProc/test.htm

[Shoe Coupe]

You mean the inaccuracy is in the speedometer gauge in the cluster. Is it normal, or a malfunction? If a malfunction, would it show up in the "cluster test"?
Videos:
YouTube "bmw cluster test"
See test 1 and test 8:
http://www.bmw-m.net/TechProc/test.htm

its not a malfunction per se, according to a BMW article, a certain % of error in speed indicated on the cluster is normal. BMW apparantly builds in some error to show speed higher in case wheel diameters and stuff are changed.

It definitely wont show up in the cluster test.

[Vintage42]

... I think the noise can come from not using enough of the paper gaskets between the plates and the body; there is a DIY somewhere that mentions that.

This is not what I was looking for, but does apply to the noise... see Msg #4 in this thread:
http://www.bimmerfest.com/forums/sho...d.php?t=429511

[Shoe Coupe]

Originally Posted by BradK
copied from SIB 620296:

SUBJECT:
Maximum Permissible Speedometer Error

MODELS:
All

General Information:
A certain amount of "speedometer advance" is necessary to compensate for negative tolerances in tire diameter, electronic controls, and other factors. This advance reduces the risk of the speedometer displaying a speed that is less than the vehicle's actual speed.
The amount of speedometer advance can be calculated by inputting a frequency (using the DIS Tester, "Kombi Test Schedule") that corresponds to a given speed and noting the speed that is indicated by the speedometer. The maximum permitted speedometer advance is 10% of the actual (input) speed plus 2.4 mph.
Example:
Actual Speed = 50 mph
50 mph x 10% = 5 mph; 5 mph + 2.4 mph = 7.4 mph
Therefore, the permissible displayed speed is 50 to 57.4 mph.
(Note: The displayed speed must never be less than the actual speed).
No repairs should be attempted if the speedometer advance is within 10% + 2.4 mph.
NOTE: The amount of speedometer advance has no effect on recording of accumulated mileage in the odometer display. The odometer records total mileage digitally and does not incorporate any "advance" tolerances.

Warranty Status:
Information Only.


hope this helps everyone!

[Pani]

Thanks for the info and advice.

Prior to the service the speedometer had about a 10-11% advance, however, now it is consistently reading 10mph higher at all speeds. At 25mph the speedometer reads 35mph which is a 40% advance!

I wonder if the computer update the shop performed could be suspect?