I think I have a Speed Sensor Issue

[FrankO]

I just drove my MH from Storage to Home getting ready for a 3 week trip. I have not driven the MH Since April but I do run Gen with Load once a month to keep the batteries up to par. All is well except that in driving the 20 mile trip I found my speed on the Scan Gauge and the Digital DIsplay to be off by almost 90%. It had my max speed at 102 when the Analog speedo showed 60. I read the write-up on the Allison 100 and it talks about 3 speed sensors (input, torque converter and output). I think my output sensor may need to have the contacts cleaned or replaced. Anyone know what I should look at or where the speed sensor is? I have a couple of days to get this straightened out. I hope Driver is lurking around
Frank O.

[FrankO]

I just drove my MH from Storage to Home getting ready for a 3 week trip. I have not driven the MH Since April but I do run Gen with Load once a month to keep the batteries up to par. All is well except that in driving the 20 mile trip I found my speed on the Scan Gauge and the Digital DIsplay to be off by almost 90%. It had my max speed at 102 when the Analog speedo showed 60. I read the write-up on the Allison 100 and it talks about 3 speed sensors (input, torque converter and output). I think my output sensor may need to have the contacts cleaned or replaced. Anyone know what I should look at or where the speed sensor is? I have a couple of days to get this straightened out. I hope Driver is lurking around
Frank O.

[Joe Gilbert]

It is certainly easy enough to check the actual speed (1 mile in 1 minute @ 60MPH). I expect you have a setup issue with your Scan Gauge.

[DriVer]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by FrankO:
All is well except that in driving the 20 mile trip I found my speed on the Scan Gauge and the Digital Display to be off by almost 90%. It had my max speed at 102 when the Analog speedo showed 60. </div></BLOCKQUOTE>FrankO. I'm going to go out on a limb and "guess" that your Scan Gauge was setup for Kilometers. Failing that your Scan Gauge is defective.

[FrankO]

Nope, it is setup for MPH as is the WH Digital Gauge. Both are reading high, AVG speed on the drive was 43 MPH and 102 Highest Speed. The reason why I think it is a sensor is because the ScanGauge and the on board digital gauge read the same. I saw my miles per gallon behaving very erratic and then I noticed the speed was say out of wack.
Any further clues? Can I hurt anything if there is a faulty sensor? I would not like to delay the trip if the problem is "cosmetic".
Frank O.

[DriVer]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by FrankO:
Nope, it is setup for MPH as is the WH Digital Gauge. Both are reading high, AVG speed on the drive was 43 MPH and 102 Highest Speed. </div></BLOCKQUOTE>Frank, I think you need to find a way to reset both gauges to zero and try this whole thing again. It just doesn't compute.

[FrankO]

Driver,
My main concern is whether anything can happen within the Tranny if the sensor is not working correctly. If not, then I will go ahead with the travel plans and try to fiddle with the setup of the ScanGauge and the WH Digital Gauge durring the travels. You know more than most about how these things work so I need your help and respect your opinion.
Frank O.

[DriVer]

FrankO,

Are you reading and comparing your analog readout on the speedometer to the digital MPH readout on the Scan Gauge?

[TandW]

When a computer controlled device acts up it can often be cured by doing a reset entailing a power disconnect for one minute. Good luck!!

[Joe Gilbert]

This does sound like a software issue. I doubt that the actual speed sensor is bad. I worked my entire career as an engeneer for the largest supplier of Hall Effect sensors into the automotive market. While a speed sensor can fail it is very unlikely that it will send incorrect data (digital pulses). It either works or it does not work. Must be a software (chassis computer)or setup issue.



Let us know what you find.

[FrankO]

Driver: Yes I did the compare and the Analog is fine - only the ScanGauge and Chassis Digital are wrong.
I agree that it sounds like software so it has to be the sender which means the TCU/ECU so a "CTRL-ALT-DEL" means disconnecting the chassis battery for a while and then reconnecting it, sound good?
Thanks guys -- Frank O.
BTW -- I should have thought of this as I have worked with computers for &gt;20 years.

[FrankO]

OK, just returned from my 3 week trip through the CO Mountains and wanted to let those interested that my issue had nothing to do with sensors or the Computer Modules. The ScanGauge that I received (from the upgrade) had a speed adjustment set that was way off. The good folks at ScanGauge helped me correct it and all is good.
Frank O.