replace steering wheel motion sensor

97Z71

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Here is some useful information about the EVO Steering system used in our Tahoe's and Suburban’s.

This system was used from 1997 until 2000 and abandon by GM partially because of problems mostly with inconsistent steering and possible legal ramifications (I have been told it was also on a handful of very late production 1996's)

First, it is called Electronic Variable Orifice Steering and works like this:

The computer monitors vehicle speed and steering wheel action to activate/deactivate a solenoid on the power steering pump. This solenoid opens and closes to control the fluid flowing to the steering gear.

At low speeds the solenoid open fully allowing full pump pressure to the steering box thus giving the operator easy steering. At higher speeds the solenoid operates and closes to restrict the fluid flow stiffening the steering. (so, power to the evo is removed at low speeds and provided at high speeds to activate the solenoid)

This system uses the steering sensor to determine the position and speed of movement of the steering wheel and uses this to determine when the EVO solenoid will open and restrict.

Troubleshooting the system:
It's really easy if you own a GM Tech 2 tool, but since most of us don't here are a few things you can try:

Jerky Steering:Unplug the (red) plug on the bottom of the EVO solenoid, this is located on the power steering pump and can be accessed from the bottom of the vehicle. Once unplugged the pump will be applying full pressure to the steering gear and you should have very easy steering that will not change with vehicle speed or wheel position. If this solved the wheel jerking replace the wheel position sensor.

I know of a few people that just left the EVO solenoid unplugged to resolve the jerky steering. Though it does solve the problem it creates a new and more dangerous one: over steering and sensitive steering at high speeds, not recommended! Fix the problem or delete the system!

EVO Delete:Knowing the error of their ways GM made a kit to delete the EVO system completely, what they did was to remove the EVO solenoid from the rear of the power steering pump and added an adapter that would allow the existing high pressure hose to be connected to the back of the pump. The part no for this kit is: 19168825 and sells upwards for about $60.00. It comes with a new power steering union and hose adapter. If you do this keep in mind you will have standard steering effort at all speeds, some really like this because it gives more of a sporty feel. The downside is your wife will probably bitch about the harder steering.

Another way to delete the EVO system (and much more cost effective) is to simply go to your local junk yard, find a pre-97 and remove the union from the pumps high pressure line, if the pressure line is in good shape take it to. These parts should cost less than 10 bucks. If the hose is shot get a new one at your local parts store, ask for a 1995 Tahoe high pressure hose. Remove the EVO solenoid from the rear of the pump , remove the high pressure hose install your replacement parts. With the car jacked up and not running operating the steering stop to stop at least 10 times, add fluid to the pumps reservoir as needed and your done!

Replacing the steering sensor: There are lots of good write-ups on the replacement of the wheel sensor so I won't go into that, one thing to mention, make sure the new sensor goes in exactly as the old one was removed, look at the old one, clock the new one exactly as the old and insert as it was removed.

One last thing, the 4x4 Tahoe, Suburban uses a 16:13:1 variable ratio steering gear (25001484). If your box is shot make sure you get the same part number, many rebuilder will give you 25001843, this is a light duty 2WD unit. It will fit but your steering will change, the zero position will also be off and will require a front end alignment to correct your steering wheel position.

Helpful Part numbers:
Wheel Sensor: Dorman Part# 31025, GM Part no:26064468
GM EVO Delete kit:26064468
Steering Gear:25001484


Happy wrenching!
Dan
 
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HANSIL59

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Read the many posts. 15mm socket. Wheel at 9 oclock. Small screwdriver 3 clicks. Nasty old foam wrap removal. Unplug - Re-plug. Click it back in place. Bolt back in. Done. Don't let a dealership charge you several hundred dollars to do this simple repair. Sure your'e upside down in the floor of your truck, but easy enough. Thanks for the details and photos.
 

rockstarchevy

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i have an 01 z71 that keeps eatin through pumps. ive replaced 3 this month. ive changed the lines and flushed the system but it just ate the last one up after about three days. anyone know what might be causin this????
 

Rondo

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I acquired a sensor from O'Reilly Auto Parts (part #31025 by Dorman) who price matched Summit Racing Equipment for $27.95 - great price. It's the Help! version. It's for a 1999 Chevy Tahoe.

I made an attempt at installing it today but was unsuccessful in getting the lower column to slide down enough to remove the old sensor. I'm no weakling, but it took me all I had to slide it about 3/4 of an inch. I gave up and put it back together which again took a big effort to get it to slide back on. Is there some secret to sliding the lower shaft down?

Thanks
 
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adios447

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Here is some useful information about the EVO Steering system used in our Tahoe's and Suburban’s.

This system was used from 1997 until 2000 and abandon by GM partially because of problems mostly with inconsistent steering and possible legal ramifications (I have been told it was also on a handful of very late production 1996's)

First, it is called Electronic Variable Orifice Steering and works like this:

The computer monitors vehicle speed and steering wheel action to activate/deactivate a solenoid on the power steering pump. This solenoid opens and closes to control the fluid flowing to the steering gear.

At low speeds the solenoid open fully allowing full pump pressure to the steering box thus giving the operator easy steering. At higher speeds the solenoid operates and closes to restrict the fluid flow stiffening the steering. (so, power to the evo is removed at low speeds and provided at high speeds to activate the solenoid)

This system uses the steering sensor to determine the position and speed of movement of the steering wheel and uses this to determine when the EVO solenoid will open and restrict.

Troubleshooting the system:
It's really easy if you own a GM Tech 2 tool, but since most of us don't here are a few things you can try:

Jerky Steering:Unplug the (red) plug on the bottom of the EVO solenoid, this is located on the power steering pump and can be accessed from the bottom of the vehicle. Once unplugged the pump will be applying full pressure to the steering gear and you should have very easy steering that will not change with vehicle speed or wheel position. If this solved the wheel jerking replace the wheel position sensor.

I know of a few people that just left the EVO solenoid unplugged to resolve the jerky steering. Though it does solve the problem it creates a new and more dangerous one: over steering and sensitive steering at high speeds, not recommended! Fix the problem or delete the system!

EVO Delete:Knowing the error of their ways GM made a kit to delete the EVO system completely, what they did was to remove the EVO solenoid from the rear of the power steering pump and added an adapter that would allow the existing high pressure hose to be connected to the back of the pump. The part no for this kit is: 19168825 and sells upwards for about $60.00. It comes with a new power steering union and hose adapter. If you do this keep in mind you will have standard steering effort at all speeds, some really like this because it gives more of a sporty feel. The downside is your wife will probably bitch about the harder steering.

Another way to delete the EVO system (and much more cost effective) is to simply go to your local junk yard, find a pre-97 and remove the union from the pumps high pressure line, if the pressure line is in good shape take it to. These parts should cost less than 10 bucks. If the hose is shot get a new one at your local parts store, ask for a 1995 Tahoe high pressure hose. Remove the EVO solenoid from the rear of the pump , remove the high pressure hose install your replacement parts. With the car jacked up and not running operating the steering stop to stop at least 10 times, add fluid to the pumps reservoir as needed and your done!

Replacing the steering sensor: There are lots of good write-ups on the replacement of the wheel sensor so I won't go into that, one thing to mention, make sure the new sensor goes in exactly as the old one was removed, look at the old one, clock the new one exactly as the old and insert as it was removed.

One last thing, the 4x4 Tahoe, Suburban uses a 16:13:1 variable ratio steering gear (25001484). If your box is shot make sure you get the same part number, many rebuilder will give you 25001843, this is a light duty 2WD unit. It will fit but your steering will change, the zero position will also be off and will require a front end alignment to correct your steering wheel position.

Helpful Part numbers:
Wheel Sensor: Dorman Part# 31025, GM Part no:26064468
GM EVO Delete kit:26064468
Steering Gear:25001484


Happy wrenching!
Dan
I am about to change out the PS pressure sensor on my 1997 Tahoe, 5.7, 4WD.

Any tricks or is it as simple as it looks. Any after installation calibration instructions?

Thanks guys, I'm a newbie.
 

97Z71

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I am about to change out the PS pressure sensor on my 1997 Tahoe, 5.7, 4WD.

Any tricks or is it as simple as it looks. Any after installation calibration instructions?

Thanks guys, I'm a newbie.

Not sure what your speaking of when you say PS pressure sensor, if your speaking about the steering wheel position sensor simply notice the orientation of the old one and install the new one in the exact same position. It is really easy to do just difficult to get to.

If your speaking about the EVO selenoid on the rear of the pump, this too is easy to remove, simply remove the retaining clip, slide the evo assembly off then remove the large fitting assembly screwed iinto the pressure side of the pump.

By the way if you want to find out if your steering sensor is actually bad just unplug the 2 wire connector on the bottom of the pump and go for a ride. Your steering should be easy and stay that way without any change. If you do this keep in mind you really don't want to leave it that way.

Read one of my previous posts on how the system works.
Good Luck!
Dan
 

adios447

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Thanks, it's the EVO power steering pressure sensor that mounts at the back of the power steering pump that I am changing. I am trying to get the steering back to not being so free at all speeds. When I remove the old sensor, am I going to have a flood of fluid to deal with?

Thanks,
Randy
 

floydwall888

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Very helpful info, thank you everyone.

I'm just starting to throw some much needed love my Tahoes way, and the strange steering behavior would have me throwing lots of money at this normally.

From the symptoms described by a few of you I can say with a high certainty that this sensor is definitely faulty on my Tahoe. The steering going "dead" has happened more than a few times, several at interstate speeds..around a corner. I'll be picking this part up over lunch and installing it this weekend. For the money, it'd be stupid not to. Hopefully it does the trick.
 

m610

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New guy. Searched. I think I found the solution to my problem so now I won't have to start a new thread and ask dumb questions.

Symptoms - power steering would cut out entirely, luckily so far only during slow maneuvers. It would also plus and sometimes seemed to want to turn the wheels the opposite direction just a bit. This indeed sounds like a flaky sensor.

Thanks for the post and the photos.

Mike
 

m610

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It turns out my Tahoe doesn't have this sensor.

Back to the drawing board.
 

bowtieman55

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BECAUSE THIS IS SUCH A GOOD WRITE-UP, I'M REVIVING THIS THREAD.

I'm having an issue with separating the steering shafts; the bell shaped one will go as far as the end of the column shaft and separate, but no further. Am I missing something here or what? Thanks.
 

rkymnt4

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power steering position sensor. I was having the same problem with my '99 Yukon SLT. It feels like you just hit a patch of ice when your turning. I did my R&R and found prices ranging from $33 to $67. Then I thought, Hey its just like a rheostat so why not shoot some electrical cleaner/lube in there? I crawled under my dash and gave it a shot and all this black stuff came out. I gave it another couple of shots until the fluid was clear and drove it around, high speed, low speed and around corners left and right and it works fine (so far). So before you go out and buy a new part, give this a try. $9 bucks is better than $33.
 

lesterl

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It will fail again...... Mine I tore apart after replacement and the wipers were worn down, the black could be the material that causes the resistance (carbon).....
 

doityourselfer

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This thread doesn't seem to cover the 2001 Yukon XL sensor. My sensor is a light gray doughnut and seems to be part # BWD S8516. Just wondering if both sensors do the same thing on other model cars.
 

DMCrawford

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So - 7-1/2 years after Lone Ranger's 1st post I replaced my SWMS too. Huge difference in steering response, from sloppy in the "11 to 1 on the clock" range to like-new tight. What a difference on curvy roads. Thanks guys.

1998 Tahoe 4WD 182K miles, new Jasper 5.8L rebuilt engine (4-bolt main) & tranny at 162K miles. Slowly but surely I am on my way to a new truck, one part at a time.
 

PL0WKING

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I'm going to tackle this job over the weekend, and I have one question after reading through all the posts here.

I noticed one member mentioned a black dust, possible being a buildup from the breakdown of the sensor, so should I clean the shaft area that the sensor itself "monitors"..?

I was thing about about giving that steering shaft area a good wipe down with some 70% isopropyl alcohol.

For those that have done this fix: Good idea or no?
 

TPinSoCal

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m610,
Did you fix your issue, i don't think mines has the sensor and still am looking for a fix
 

lesterl

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What year is your rig, 1996 and older dont have the system... Lucky dogs.....
 

TPinSoCal

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2001, I took the shaft apart and pulled the plastic end cap / bearing off and no sensor was installed?
 

Roballa

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So I have on 03 yukon and can't find any wires to the sensor.. And the sensor is missing from the plastic housing. Is this a different style of sensor?
 
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