Whats the best way to correct the speedometer? - The Unofficial BMW M5 Messageboard (m5board.com)

Kmac · 6th March 2008, 03:37

The delta between my actual speed (GPS derived) and my speedo is annoying. I have read that the BMW speedo reads between 8 and 10% high. I also read Alex Roy's book where he installed a sensor (wheel something) and it had a digital readout of his actual speed.

Is there a way to correct the speedo or do you need to go aftermarket and use the wheel speed sensor?

6spd · 6th March 2008, 04:11

I have been looking into this also, I don't know if its possible to adjust it in the dash cluster test 07.3 or 07.058(one of those two).

First the mars lander calculations and now BMW speeds, It must have been the same NASA employee.

Kmac · 6th March 2008, 04:58

Quote:

Originally Posted by 6spd

I have been looking into this also, I don't know if its possible to adjust it in the dash cluster test 07.3 or 07.058(one of those two).

First the mars lander calculations and now BMW speeds, It must have been the same NASA employee.

lol - and you are waaaay farther into this than me. I assume that the input is digital?

6spd · 6th March 2008, 07:12

I will try to find the instructions again, I had to run off to a softball game so I couldn't look for them earlier.

E39 Instrument cluster test functions

Test functions

Menu	Sub menu	Sample	Meaning
Test 1: Vehicle specific data	1.0	12345	VIN
	1.1	4812	Body number
	6_1.2	834762	Part number of cluster
	1.3	010203	Coding/Diagnosis/Bus index
	1.4	3495	Manufacturing data (calender week/year
	1.5	04_600	Hardware/software number of cluster
	3_1.6	415_06	Injection status, number of cylinders, engine factor
Test 2: Cluster system test			Activates test for gauge drivers, indicators and LEDs
Test 3: SI data	3.0	1500	Litres
	3.1	0	Periodic inspection days (not applicable for US)
Test 4: Fuel consumption data (current)	4.0	0267	26.7 litres/1000km
	4.1	0073	7.3 litres/hour
Test 5: Fuel consumed/distance travelled	5.0	0195	19.5 litres/100km
	5.1	226	Momentary distance to go (22km)
Test 6: Fuel level sensor input in litres	6.0	237415	Fuel level averaged. LH sensor input = 23.7 litres - RH sensor input = 41.5 litres
	6.1	0652	Total tank level averaged = 65.2 litres
	1_6.2	0667	Indicated value and tank phase. 1 = Both sensors OK. 2 = One sensor fault.3 = implausible input
Test 7: Temperature and speed	7.0	032	Coolant temperature input 32C (90F)
	7.1	245	Outside temperature input 24.5C (76F)
	7.2	5283	Engine speed 5,283 RPM
	7.3	085	Vehicle speed 58 km/h (36 mph)
Test 8: Input values in HEX code	8.0-8.3	XXX	Hex code, instrument cluster inputs
Test 9: battery voltage	9.0	125	12.5 Volts
Test 10: Country coding	10.0	02	US 02
Test 11: Cluster code	11.0	000003	Cluster code
Test 12: Not used
Test 13: Gong test	13.0	GONG	Activate gong by pressing button (gong response is delayed)
Test 14: Fault memory (not used for diagnosis)
Test 15 - 18: Not used
Test 19: Lock/unlock	19.0	L-On L-Off	Lock/unlock specific test functions
Test 20: Average fuel consumption correction factor	20.0	XXX9	Press button when correct 1s position is attained
	20.1	XX5X	Press button when correct 10s position is attained
	20.2	12XX	Press button when correct 100s position is attained
Test 21: Software reset	21.0	reset	Reset software

Instrument cluster, self testing
Perform the following steps to access the instrument cluster self test functions:

Remove and insert ignition key (ignition OFF)
Press and hold RIGHT cluster button. “CHECK CONTROL OK” is displayed.
Without releasing button, turn ignition switch to first dent (RADIO position). “TEST-NR. 01″ is displayed.
Press LEFT cluster button for the test sub-menus.
Press RIGHT cluster button to scroll to next test.

Note:
Test 1 and 2 are always unlocked
Test 3-21 are only accessible after unlocking using TEST-NR. 19 lock/unlock function. See Instrument cluster self test, unlocking.
Instrument cluster self test, unlocking
To unlock a specific test:

Remove and insert ignition key (ignition OFF)
Press and hold RIGHT cluster button. “CHECK CONTROL OK” is displayed.
Without releasing button, turn ignition switch to first dent (RADIO position). “TEST-NR. 01″ is displayed.
Use RIGHT cluster button to scroll to TEST-NR. 19 (lock/unlock)
Press LEFT cluster button once to access TEST-NR. 19 submenu. “LOCK : ON” is displayed
Use LEFT cluster button to scroll to test you wish to unlock.
Press RIGHT cluster button once to unlock desired test. Display returns to TEST-NR. 01.
Scroll to unlocked test using RIGHT cluster button.
Press LEFT cluster button to perform desired test or access that tests submenu.
Repeat unlock sequence for each test required.
Switch ignition OFF to cancel self test mode.

Note: Display shows no visual confirmation of test unlock.
Instrument cluster, software reset
To reset instrument cluster software:

Remove and insert ignition key (ignition OFF)
Press and hold RIGHT cluster button. “CHECK CONTROL OK” is displayed.
Without releasing button, turn ignition switch to first dent (RADIO position). “TEST-NR. 01″ is displayed.
Use RIGHT cluster button to scroll to TEST-NR. 19 (lock/unlock)
Press LEFT cluster button once to access TEST-NR. 19 submenu. “LOCK : ON” is displayed
Use LEFT cluster button to scroll to TEST-NR. 21. “LOCK : 21″ is displayed
Press Right cluster button to unlock TEST-NR. 21. Display returns to TEST-NR. 01.
Use RIGHT cluster button to scroll to TEST-NR. 21.
Use LEFT cluster button to access TEST-NT. 21 sub-menu. “REST ?” is displayed.
Press LEFT cluster button again to perform reset.
Switch ignition OFF to cancel self test mode.

Note: Display shows no visual confirmation of test unlock.

Thank you to KinMak for having posted this else where.

Alin10123 · 6th March 2008, 10:47

Could it be possible that there's a difference between the nav and speedo speeds because of the up and down grades of the roads? The GPS probably doesn't know if you're going up a grade or down a grade, would that make it possible there's a difference in speed, along with the wearing down of the tires decreasing the outer circumference of the tires?

Kmac · 6th March 2008, 15:19

Quote:

Originally Posted by Alin10123

Could it be possible that there's a difference between the nav and speedo speeds because of the up and down grades of the roads? The GPS probably doesn't know if you're going up a grade or down a grade, would that make it possible there's a difference in speed, along with the wearing down of the tires decreasing the outer circumference of the tires?

Good thought, but its a known fact the speedo is off. At least according to the wheels that are on your car, which are rather important in determining speed. And you are right, if the circumference of the wheel changes, it has more revs per mile and I have no idea if the wheel speed sensor adjusts for this.

Maybe I should try a wind speed gauge on top of the car

Kmac · 7th March 2008, 07:23

That speed in 7.3 must be a calculated item. I wonder if its using a pre-determined wheel revolutions per mile, that changes depending on the tires, etc. If it bases the number on a tire that we no longer use, that could cause an inaccuracy. Next, you have to wonder if it could be changed. The number that is in there would look like 788 or something to that effect give the standard tire sizes.

I wonder what the standard tire sizes are for european models?

Also, did you see that in speedo accuracy ratings, BMW was dead last!!!

Kmac · 7th March 2008, 07:45

Found the answer.

http://www.atrol.com/era.htm

E55AMG2 · 7th March 2008, 07:53

The error is programmed into the cluster itself. Mine is a constant 3mph. The OBC "average speed" reading is dead on accurate when compared to GPS.

Kmac · 7th March 2008, 08:18

Quote:

Originally Posted by E55AMG2

The error is programmed into the cluster itself. Mine is a constant 3mph. The OBC "average speed" reading is dead on accurate when compared to GPS.

Nice - I just read that somewhere else also. I wonder if they are reading from two different sources (one from the tranny, one from the wheels?) or if there is a build in + function between the OBC and Speedo.

My guess is two different sources. You also had to convert from m/s to mph correct?