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Transmission input speed sensor


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I am getting intermittent codes on the 96 aurora for the transmission input speed sensor. I have looked on alldata to find the location of the sensor but I cannot find a good illustration, alldata does say that the transmission must be removed to service the sensor.

Is this true? I sure hope not, I would like to find the wires at least going to the sensor to look for breaks in the insulation / shorts and try to fix it.

Any help is appreciated.

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Thanks, i found the same with a little searching. As it is intermittent, It could be a plug or wire going to the sensor. I need to find a diagram that shows the plugs detail and maybe the wire routing.

This code will prevent the shift adapts and the tourque converter from locking. My wife does not like the way it drives, so I will look to fix it.

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Not for the weak at heart......here is a 'in car' repair for the trans input speed sensor (not vehicle speed sensor)....


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Thanks for the link, I did not even bother to check bruce's site. The procedure looks a little daunting, but I should be able to do it. The only problem is that we rely on the car and the repair has the potential of taking more than a weekend to do right.

I wonder if the sensor is going bad of if the spacing has just been compromised.

I will have to think about it - the light is off right now. Maybe it will stay.

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  • 4 weeks later...

Here is an update:

I ordered service manuals off of ebay and a transmission tech manual off of Jc Whitney, both are good buys. The tech manual had some clear diagrams of the plugs, locations and corresponding circuits.

I was performing an oil change and swapping the oil pressure gauge on the Aurora today and decided since I was dirty, that I would check to see if I could find the transmission input speed sensor wire.

After a lot of contorting, I found that I could access it by removing the radiator - but that seemed like a lot of work you can also get to it pretty well by removing the lower splash shield.

The connector was covered with oil and upon uncoupling the plug, oil started dripping our of the individual holes that the pins insert into. How the oil got in there is another story. I used a toothbrush, degreaser and compressed air to clean out the holes.

Upon reconnecting the plug I restarted the car and the light disappeared. It may reappear, but it is possible that the oil was coating the conductors causing problems. I also noticed that the wires going to the plug make an extreme bend offering no stress relief for the wires - that may eventually cause problems as well

I hope this simple repair works, I am really not looking forward to the official repair.

A side note, I did some searching on the low oil pressure message and noticed a lot similar threads where the original poster got some advice and then never got back to the group with an update on wether the problem got fixed. I think a lot duplication of questions could be avoided if the orignial poster would update the gorup with the results.


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Hope the plug cleaning works for you. I have the same symtoms with my Eldorado, and I know what you mean about the dive-ability. I'll keep an eye out for your feedback on the long-term results. I agree, everyone should try and make an effort to report back findings whenever possible.

Mine isn't that bad, but it really bothers my wife when she drives the car when that codes is active. It idles higher when you put it in gear, and shifts quite a bit firmer...

'09 Cadillac CTS-4 3.6 direct injection, 128 K mi.
'15 Chevy Tahoe LTZ, 5.3i V8, 125 K mi
'70 Firebird Formula 400, Bored+.04, RAIII heads, M21 4spd., in-process restoration!

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  • 5 months later...


well the problem came back, but I am pretty sure of the culprit - the water pump! The cables leading into the trans route underneath the pump, got the low coolant light the other day which led me to this discovery.

I figure the aurora had a small leak from the pump for a long (years) time. That side of the splash guard was always dirty and damp. I figured it to be the radiator drain plug or a hose. I never gave it much thought.

I pulled the airbox, splash shield and more off last night to find that the plug was again saturated. Water leaks onto the wires which lead into the plug. Capillary action in the plug holds the moisture in. I cleaned it out with compressed air and let it dry. I took it out today and again the light is gone.

Looks like I will need to change the pump, the leak is getting worse anyway.

Hope this fixes the problem.

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