[Sumedik]

Hello SupremeBaleno, it is good to see you are close to solving the issue. Since a single front wheel sensor fixed the Speedometer and Odometer issue, it seems that in Astar AT vehicle speed is determined by a single ABS sensor only. This is surprising to me, since I was expecting that the average of 2 front wheel sensor inputs would determine the correct speed of the car ! After all different wheels rotate at different speeds during various instances of the drive; that's the reason cars have 4 ABS sensors anyway.

I too suspected the lethargic function of the speedometer after it started working, looks like i did not imagine it after all !

Replacing of the Right Front Wheel ABS sensor should switch of the ABS warning light, just like it happened in my case. Please try that before touching the rear wheel sensors.

I wonder why your ABS issue was not diagnosed earlier, in my case OBD2 scanner available in MASS straightaway showed the 2 relevant error codes indicating the front 2 ABS sensors have failed. Also in live data mode, the OBD2 scanner picked up 0 speed values from both the front wheels during test drive.

Regarding GSD, truly nobody in Maruti India seems to know its exact functionality; I have enquired enough. Based on my research I believe that the AT gearbox makes shift decisions (via ECU) by comparing gearbox output shaft RPM (captured by GSD) rather than actual wheel RPM (captured by ABS sensors) to current engine RPM (captured by Sensor, Speed Input). That is why the GSD is mechanical rather than magnetic, as this would ensure more accuracy.

Do keep us posted.

[supremeBaleno]

Originally Posted by Sumedik

Replacing of the Right Front Wheel ABS sensor should switch of the ABS warning light, just like it happened in my case. Please try that before touching the rear wheel sensors.

Agree. I have been trying to source the front right wheel sensor, but not in stock at outlets near me. Boodmo seems to have it, but the pic doesn't look like the sensor.

Originally Posted by Sumedik

I wonder why your ABS issue was not diagnosed earlier, in my case OBD2 scanner available in MASS straightaway showed the 2 relevant error codes indicating the front 2 ABS sensors have failed. Also in live data mode, the OBD2 scanner picked up 0 speed values from both the front wheels during test drive.

My FNG didn't have scanner, so obviously he couldn't diagnose it. I had taken it to the local MASS also, but they didn't use the scanner (not sure why). It has since visited MASS few more times, but for some reason it wasn't diagnosed/rectified. Since braking worked fine, I also didn't go chasing the issue much. Hopefully replacing both front ABS sensors will finally fix it.

[supremeBaleno]

Originally Posted by Sumedik

I too suspected the lethargic function of the speedometer after it started working, looks like i did not imagine it after all

Do you see the lethargy even after changing both the front wheel sensors ? In my case only left front sensor was changed, so I guess it could be due to right-front sensor being bad.

Last weekend I again took out the car for a drive. For the first 10metres or so, no movement of the speedo needle - glued to 0 position. Then needle started working like normal - tested till 80kmph. Odometer works fine, though I did not remember to check during the initial 10metres (was focussed on the speedoneedle).

[Sumedik]

Hello SupremeBaleno, in my case both the front wheel ABS sensors were replaced concurrently as we had previously detected (via OBD2) that NONE of those 2 sensors are sending any wheel speed inputs. So I do not have any insight on single front wheel sensor input based Speedometer behavior.

If you can manage, scan using an OBD2 scanner which can capture ABS modules before making further replacements. A suggested domestic setup would be an iCar Vgate scanner (available on Amazon at reasonable price) paired with SZ Android app.

My Speedometer lethargy issue seems to have gone now; maybe it was a case of things being too rusty due to prolonged non usage.

Keep us posted & stay safe.