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Discussion Starter #1
I have a 2002 beetle 2.0 with automatic. The speedometer indicates about 45mph at 70-75 mph when cold and 25-30 when hot at 70-75 mph, I have been using the tach to drive by(it appears to be ok). the odometer is only picking up half the distance traveled, about equal to the speedometer, the cruise control surges as well, I think its from improper signal to the cluster. I have replaced the speed sensor in the trans under the mount, no change.
Could this be related to low fluid in the trans?
Does the other sensor on top of the trans signal vehicle speed too?
Any way the gear for the sensor could be slipping?
I have also read about needing it calibrated, but want that to be last to check as I can do most of my own work.
Any ideas would be greatly appreciated.
 

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First, I would start with a fresh scan with a VW compatible scan tool and see if there are any trouble codes. As for the cruise not working; I have seen brake light switches and bad connections inside turn signal stalk, kill the cruise control.

Speedo failures; are becoming more, more common, as our cars are becoming older. If you have a scan tool; that shows live data from the obd II connector, you could check and note, if the computer can "see" the right mph or if it is the same as what the speedo is showing. If it is different; than, I would say that would isolate the speedo from the ecu data and the speedo would need repaired. What we have been seeing; is that the stepper motors, get old and eventually fail, plus components on the inner circuit board are dying as well. Problems with the speedo; could possibly cause problems with the cruise control but we haven't seen that here so far.

The better VW specific scan tools; can run output tests on the speedo cluster and see if the stepper motors, sweep the full degree they are made to.

Check out this thread; for repair info and output test examples on video: http://newbeetle.org/forums/2-0-liter-gas/128361-instrument-cluster-interchangeable.html
 

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Discussion Starter #3
Won't scan

well tried my buddy's scanner wouldn't work also tried the Autozone, comes up Error...
time to unhook the radio and try again ( blue wire I have read needs clipped ) anyone know what the blue wire is for?
 

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Discussion Starter #5
Okay I disconnected the radio wire and got a scanner (BT), scanner is able to talk to the ECU and reset codes ok. reading the speed on the road it shows the same as the display cluster, i'm thinking it's in the tranny or something to do with the sensors or a calibration of some kind.
Any new thoughts?
 

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Factory calibration is about 5 MPH; off than actual speeds. I do not think it is a calibration issue; as you are saying the speed is varying widely, hot/cold etc. Is this still the way it is; according to your scan tool?

Again, a VW specific scan tool; could give you some specific trouble codes, that point you in the direction of the problem.

Your transmission; is the 01M 4 speed, I have heard of the speedo gear getting damaged and needing replaced. Based upon the description of your problem and this thread, it sounds like it could be the gear. They are saying either trans removal or careful axle, bearing removal is needed to do the job.

VWVortex.com - Mk4 01M Spedometer Drive Gear DIY

Before going that deep; I would want to make sure, it isn't a speedo sensor, that is connected to the speedo gear. Other people, have referenced the G22 speed sensor falling apart and needing repaired or replaced.

Check out this video:

https://www.youtube.com/watch?v=7ryOUaHuHZ0

It seems the G22 sensor; is the one for the cruise and speedo: (look at location photo):

Kansas City Tdi & CoolAirVw Repair

sensor: VW part # 357919149B

https://www.ecstuning.com/ES335235/?gclid=CjwKEAjw-_e7BRDs97mdpJzXwh0SJABSdUH0NFAsEHsV5NZDZZggKpKRlvdPUSwEuWQ7X4Mse5kSBBoCKvPw_wcB

Good info for the 01M:

http://wiki.ross-tech.com/wiki/index.php/4-Speed_Automatic_Transmission_(01M)

General Notes

The 01M transmission has 3 speed sensors which are found in the repair manual however TSB 01-99-02 clearly describes the location and function of the sensors (G38/G68/G22).

http://www.rialtainfo.com/vw/vw_images/tech_bulletin_01-99-02.pdf

Vehicles with (G38/G68) specific speed sensor faults may have applicable TSBs for overlay wiring harnesses.

Jetta and Golf (9M/1J) platforms would refer to TSB 01-07-09 for G68 faults and TSB 01-06-23 for G38 faults.

New Beetle (1C) platform would refer to TSB 01-07-17 for G68 faults and TSB 01-07-16 for G38 faults

The 01M transmission has a plastic speedometer drive gear inside the transmission which operates the driven gear connected to the G22 VSS sensor. When the transmission has internal failure of the drive gear the common concerns include inoperative cruise control and/or speedometer.
 

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Discussion Starter #8
ok now have replaced the G22, G38 and G68 sensors.
Still no change in problem.
With the scan tool hooked up running Bluetooth to a tablet I can watch the OBD2 speed and GPS speed. There was two separate times that the OBD2 speed showed correct but the display cluster had no change. But most of the time OBD2 shows the same as the cluster, which is almost half the correct speed and mileage.
I wonder if a dealership would have the capability to hook up the sensor wires and input to the system values to determine if it is in the trans or not. Or does Fixmyvw.com have rentable equipment, guess I'll have to ask them.
 

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Was the G22 sensor; damaged, like in the video? Your internal gear; maybe, the issue at this point? Its either the speedo or the G22 sensor; where the speedo is getting the data to display. Seeing how the OBD II data is off; I would assume, something related to the sensor data acquisition is compromised?

I think fixmyvw.com; will rent out VCDS for a fee.
 

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Discussion Starter #10
It's been a while

Still haven't gotten it fixed, but I think I have it narrowed down to what it is. Now that winter time is here and its cold outside. I noticed that when the tranny is cold the speed matches GPS dead on, but only when it's cold, after a minute or so the speed drops off like normal as stated above. This kinda tells me from other articles I have read it could be the sensor gear. The oil cold makes the gear turn normal and when it gets warm/hot it slips causing the speed to appear to drop. I plan on talking to a garage to see what it will cost to have it replaced. I have read these gears are plastic and go bad all the time. Wish me luck.
 
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