: calling yukon guys....overboosted steering

11-23-08, 01:25 PM
My fellow GM truck owners....the sister to your rides, our 01 Denali, has overboosted steering recently. Very light effort to turn.

No jerking or catching. No codes. No grinding. Just super easy.

Now i read about a steering sensor,
but that part number only went up to '00s.
Does the 01 have something similar? What can my issue be? thanks!

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11-24-08, 11:40 AM
My wife has an 01 Yukon Den with some steering issues. If you make a left turn, the wheel returns to normal like it should. If you turn right, the wheel just stays there until you bring it back like you're driving a semi. Its also easier to turn the wheel right than left. Alignment and everything has been checked and the caster (part of the alignment that makes the wheel return to center) is nominal according to Midas. That's a good post on the other forum. If a couple guys are changing a $30 part on their lunch break and correcting the problem, I might give that a try.

Urbanski, I'm not sure what you're asking when you say does the 01 have something similar? Are you looking for part #s or something else?

11-24-08, 11:50 AM
that part number only goes up to '00 Yukons...and I didnt turn up a '01 part on rockauto, etc.
So I didnt want to buy something that's not for my ride.

I have read about your issue as being another sensor, EDS or something.

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11-24-08, 12:15 PM
Did you read about that on the caddie forum here or that chevy forum? I joined and searched over there for EDS, but nothing came up. Same with this forum. Please let me know.

11-24-08, 05:11 PM
had the same problem on my 00 escalade.... turned out to be the "pitman arm", a $600 repair with an alignment.... the steering was very very loose... it got progressively looser and looser each passing month... i eventually ended up bringing it in

11-24-08, 05:36 PM
Did you read about that on the caddie forum here or that chevy forum? I joined and searched over there for EDS, but nothing came up. Same with this forum. Please let me know.EVO sensor. I read it over there.

had the same problem on my 00 escalade.... turned out to be the "pitman arm", a $600 repair with an alignment.... the steering was very very loose... it got progressively looser and looser each passing month... i eventually ended up bringing it in
egads, hope its not that!

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11-25-08, 09:45 AM
Yea, I hope I don't have a problem with my pitman arm either. I can think of better things to do with $600 other than replace that thing.

Urbanski, after reading several of the other posts on tahoeforum.com, I'm thinking the steering wheel position sensor is my problem, not the EVO. That's about a $60 part for the Yukon so I'm thinking I'll try that and see what happens.

And you're correct, I couldn't find that part on rockauto either, but gmotors.com can ship one to me for $60.

11-25-08, 10:28 AM
dig, are you going for it? if you order it, give me the part # please. For 60 i almost dont care if it doesnt fix it.

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11-25-08, 02:37 PM
I have a vague recollection of having similar symptoms on my 01 Tahoe. As I recall, under the GPMM, they replaced a steering position sensor. I will try to dig up my old records at home later to 100% confirm, but I fear I may have tossed them when I sold it in 06. Good luck.

11-25-08, 10:41 PM
Hay urb, did you check w/EWill? He might have some insight.

11-26-08, 06:54 AM
They deleted EVO steering around that time but I am not sure what specific years they did it.

Sometimes the sensor would glitch and the EVO would go to full boost, usually in a turn.
To know if you have EVO steering just look at the pump.
On the back where the pressure line comes out there would be a solenoid attached to the fitting and I think it would have a red two wire electrical connection. If it is just a pipe and a small flat fitting then you don't have EVO steering.

Most non-Y91 (not an Escalade) vehicles don't have the fancy schmancy stuff that the Escalade does so you might not even have variable rate steering. It probably does have a steering sensor but that would be used with stabilitrak if you have it.
I can't remember if it is JL9 or JL4...

If the steering is just too easy all the time you could have pump or gear issues.
Does this have a hydraulic brake booster or a vacuum booster?
Usually those gears fail with no steering at times, not too much.

More to follow, gotta run right now.

11-26-08, 08:18 AM
Thanks, Bill. You da best! (Imaginary REP points!!)

11-26-08, 09:20 AM
Sorry urb, my records are nowhere to be found.

11-26-08, 09:32 AM
thanks guys. mystery deepens.

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11-26-08, 04:30 PM
Urbanski, part # from gmotors.com is 26084178 Steering position sensor $53.76 plus $11 shipping. That's for an '01 Denali. I haven't had time to check ewill3rd's suggestion to see if there is an extra solenoid on that PS pump or not. If you purchase the part and have any luck, let me know.

11-26-08, 05:15 PM
will order it, thanks :)

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11-26-08, 09:27 PM
I didn't mean to imply that the solenoid could be faulty. I have honestly never seen one go bad.
The issue with EVO is usually a glitching sensor causing the EVO module to react by turning the solenoid off and causing full boost which can cause an oversteer condition.
I intended that information to be used as a starting point to see if the vehicle even had that feature.

I was hoping to hear a better description of the original issue.
And what type of brake booster system this vehicle has.

11-26-08, 10:01 PM
ewill3rd...the issue with my yukon is if I make a left turn there is (what seems like normal) resistance and if you let the steering wheel go, it returns to center. If I make a right turn, its super easy to turn the wheel, but the wheel just stays put if I let it go so I have to bring it back to center like I'm driving a semi. I've had an alignment, chassis lube, replaced a couple ball joints that had busted boots and the problem is still there. The tech who did the alignment said the caster is nominal as I asked him specifically about this issue. So I read a couple posts saying replace the steering wheel position sensor...

To test to see if my sensor is bad, I unplugged it the other day and the feel of left and right turns is now more uniform than with the sensor plugged in. There is less resistance to a left turn and the wheel does not want to return as much as before. Right turns were pretty much unaffected by unplugging the sensor. So it seems like unplugging the sensor got rid of the boost?

What do you think...will changing the sensor fix my issue? A guy on a different forum had a 99 Denali and said when he changed his sensor, it seemed like the system now had "lots of caster" and tightened up to a sporty feel. That sounds great to me as I almost ran into a curb after overshooting a right turn b/c I normally just let the wheel slip through my hand when returning to center. I'm not sure if the 99 Den has the same steering system as the wife's 01 and no one has been able to confirm this for me.

So that problem seems a little different from Ubs' where he has fulltime overboosted steering that I'm assuming feels very loose.

11-27-08, 06:02 AM
I was hoping to hear a better description of the original issue.
And what type of brake booster system this vehicle has.

better description!!!???? its too damned easy to turn the wheel :p

and regarding the brakes, i wouldnt know a vacuum from a hydraulic from a chipmunk on steroids :hide:

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11-27-08, 08:07 AM
Is it way too easy or just a little?
Open the hood and look at the master cylinder. What I need to know is does the booster look like a small cast iron block with hydraulic lines going to it or does it have a large round flying saucer looking thing with a large vacuum line going into it on the inboard side just above the master cylinder.
While you are under there, look at the power steering pump, find the two lines on it, and look to the one on the back side of the pump. See if there is a solenoid on there or not, snap me a photo maybe?

Urby, too much assist all the time can only be caused by a couple of things. One would be too much system pressure or flow. The flow control valve in the pump could be stuck or something of that nature. I don't see that often. GM does have a tool that allows us to test system pressure and flow to isolate the cause of the issue.
The other thing could be the piece inside the steering gear. There is a small torsional rod inside the gear with a valve on it. The twisting of the rod causes pressure to flow through the gear to give you assist in the direction you are turning. If this torsion rod is weak or damaged it can move too much causing a bit too much assist on turns.
Both problems are pretty rare and frankly it is almost the toss of a coin as to which one is really bad.
Sadly I think both are expensive to fix. If you had hydro-boost (the cast iron booster with hoses on it) this could be a more complicated issue but a pump problem should affect the brakes as well to some degree.
I bet you could tell a chipmunk on steroids from a brake booster... you don't give yourself enough credit.... lol

11-27-08, 08:17 AM
digital, your problem could be similar to urbys issue. The caster in the alignment should help force the wheels back straight after a turn. If the alignment has been done you should be okay... I am not really an alignment guy so I can't really throw any super great information your way.

The key to finding out what your problem might be is knowing exactly when this occurs. If it is at highway speeds on long turns then EVO could be an issue and the SWPS could be a suspect. If it happens below say 20 mph then I doubt EVO has anything to do with it.
EVO does nothing below a certain speed, and I don't know what speed that is off the top of my head. To add to that the manual doesn't say.

It looks in the manuals like both of these vehicles COULD have EVO and if they do it certainly can't hurt to replace the SWPS. It isn't that hard and it CAN fix issues with assist at higher speeds.

I guess you guys could try the sensors and go from there.
I can't say one way or another that it will fix your issues but barring me being able to actually put my hands (and test equipment) on them I can't really give you much more right now.

12-01-08, 03:05 PM
Thanks ewill. I can take/post some pics either tonight or tomorrow as I'm not completely sure what you're describing. The brakes seem fine. If Urb pulls the trigger on this sensor and has some luck, I might do the same thing unless you see something in the pics that indicates I don't have the EVO steering. I didn't see 2 red wires coming off the power steering pump, but maybe I wasn't looking in the right spot and/or I'm not exactly sure what I'm looking for.

12-01-08, 03:16 PM
Oh, and to be a little more specific, I notice the wheel not returning to center after slow (15-20mph) righthand turns and, now that I disconnected the sensor, there is less push back after making lefthand turns. As far as the wheel turning easily to the right, I'm not sure if its "way too easy" or just "sort of easy". I would have just chalked all this up to SUV steering if there wasn't a noticeable difference in the effort it requires to turn left compared to right. My Escalade has uniform steering feel and the wheel pulls back to center if you let it go after making a slow turn. My father-in-law's 02 Silverado drives the same. Left turns with the sensor plugged in seem normal i.e. there is moderate resistance. Some of the resistance goes away with it unplugged which is where I left it so the right and left respond similarly although there is still a difference.

12-02-08, 06:49 AM
Actually what I meant to say was where the line goes into the pump (pressure hose) there is a red connector with two wires in it.
I think it is red.
If I see one I'll try to post up a picture, I murdered one of my digital cameras yesterday though :(
I crushed the screen by accident.
It still works but....

12-02-08, 02:14 PM
Ewill...all these pics are taken with me standing right next to the driver's front tire looking into the engine area. Front of the truck is on the left of each pic, firewall is on the right, driver's front tire toward the bottom, passenger's front toward the top, etc. Let me know if that's what you're looking for or if I need to take some more.

Sorry to hear about your camera...those things sure are handy though.

12-02-08, 02:17 PM
mine looks about the same

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12-02-08, 08:48 PM
Picture 3 shows the pressure hose coming from the pump to the gear.
See how the fitting goes in to the gear with a manufactured pressure crimp, the other has a cheesy spring clamp on it, that is the return hose.

Follow the pressure hose around and behind that shield to the back side of the pump, going to be hard to see back there. Where that line attaches to the pump there should be a solenoid and connection IF it has EVO.

I also see a vacuum brake booster on the right in picture two.

12-03-08, 10:24 AM
OK, thanks. I'm thinking the best way to see where that hose goes is to look beneath the truck which means I'll have to remove a skid plate, but that's just a couple bolts. How big is the solenoid? Can of soup size?

12-03-08, 09:16 PM
No not nearly that big, maybe the size of a small spool of thread?
diameter of about a nickel, and about 3/4" long?
I am not convinced that EVO is your issue though.
I wish I was better with that particular kind of stuff but we don't see too many trucks and it has been almost 5 years since I worked for Chevy or I might have some more tips for you.

12-12-08, 10:15 PM
Urb...any updates with the sensor? I've been trying to find time to get underneath the truck and hunt for that solenoid, but its been snowing here and my garage doesn't have a floor drain which means that its cold and full of puddles of melted snow. Yick...

12-13-08, 06:28 AM
nope, sorry, no time to work on anything lately

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12-23-08, 11:50 PM
ewill...I traced the hose coming off the pump around to the part circled in the pic. Is that the solenoid you're talking about? If so, this confirms that I have EVO steering and changing the sensor above the pedals on the steering column could have an effect? If no, do I need to take another pic or what do you think? Please let me know and Merry Christmas.

12-24-08, 06:36 AM
You are getting a lot closer, it is on the other end of that black adapter.
It is kind of tight back there, you almost have to get back in there for the ability to photograph it.

12-24-08, 06:44 AM
I don't know why I didn't think of this before.

If you have this, then you have EVO, if you have a line that goes straight into the pump, you don't.

01-02-09, 02:38 PM
ewill...this might be a stupid question, but I'm still a little confused with this system. So if I have EVO steering, the pump that is in pic #3 from post #25 in this thread (my post from 12-02-08 1:14pm) should look like the sketch that you posted? Those do not look similar to me indicating that the Yukon doesn't have EVO steering. If I'm looking at the wrong part, where should I find what's in the sketch you posted? Thanks in advance.

01-06-09, 08:32 AM
Pic 3 is the front edge of the pump, that image I posted it a view from the back.
You just have to get to the back side to see if the solenoid is there.
In the picture in post 32 I see the fitting that goes to the solenoid valve, if this was a non-evo vehicle then the pressure hose fitting would go straight to the back of the pump, not to that fitting that I can clearly see.

01-07-09, 04:00 PM
Thanks, ewill. I'll take a look back in there to see if I can spot the solenoid just to confirm, but it sounds like that truck does have the EVO steering. I'm getting to the point where I think dropping $60 on the part is worth a shot. It helped that I got through the holidays cheaper than expected mainly b/c I found a bar on NYE in downtown Chicago that had $1 well drinks...that saved a lot of cash.

01-15-09, 07:17 AM
lol, well good luck with the repair.
You are talking about replacing the Steering position sensor right?
I have never seen a solenoid fail, unless someone dropped the pump on it.

01-15-09, 03:22 PM
yea, I ordered the steering wheel position sensor from gmotors.com and received it yesterday. I'm outta town for about another week and will install it when I get home.

Do you know if that sensor has polarity to it or is there a wrong way to install? I read a post on another forum saying its easier to remove the carriage bolt in the steering column if the wheel is turned 180 degrees. I don't know if that means that I need to spin the sensing portion of the sensor to compensate or just stick the thing in there. Any suggestions? Thanks in advance.

01-21-09, 06:50 AM
Start the truck and turn the wheel to remove the nut on the I-shaft inside, then turn the wheel back to straight.
There is a small horseshoe shape that needs to stay at 12 o'clock when installed.
Put the shaft back in after you do the sensor (yes it needs to be straight and clocked properly) and then put the bolt back in, turn the column for access to the bolt again if needed.
The wheel must be straight ahead when doing the sensor, don't turn the wheel with the I-shaft disconnected, and be sure it is in the exact position it was when you disconnected it when you go to reconnect it.
Any deviation can break the SIR coil and cost you $$$.

02-01-09, 12:31 PM
OK, fellas, it finally warmed up here enough that I was able to install the steering wheel position sensor. Turns to the left stiffened up to where it feels nominal (a nice change), turns to the right still feel overboosted and the wheel still will not return to center so I must have some other issue. The steering column on that truck is not perfectly round so the sensor can only be installed one way or 180 degrees from that position. Ewill, does it matter which way I installed it? I tried both methods and there is no difference in the way the steering feels... And there didn't appear to be any marks or arrows or anything else indicating that the sensor is in correctly or 180 degrees off.

Urb, if you do this install, it helps to turn the wheel 90 degrees left to get the nut facing down so you can get it loose, then turn the wheel back to straight and remove the nut and bolt, then push the universal joint toward the firewall. Next use a flat screwdriver or something similar to take 2 of the 3 tabs loose on the retainer holding the steering wheel position sensor in place and then work the 3rd tab on the top loose. Slide and old sensor down and off and you're in business. I found it easier to kneel outside the truck rather than lay on my back by the pedals and try to work over my head. Wish I had some better news to report, but this part didn't do a whole lot for me.

02-01-09, 06:14 PM
The old sensors had a small horseshoe shaped indentation at the top on the outer part. The housing points so that the connector is in place and the horseshoe is at the top with the wheel straight ahead.
It has been a while since I did one and they may have changed the parts.
I don't think on that older EVO system it is as critical to have the sensor centered as it is on most newer car applications.
It sounds like you have something different going on here.
When was the last time someone checked all the alignment specs on this thing?
It almost sounds like some sort of caster problem.

02-02-09, 05:02 PM
thanks digital. ours too feels pretty back to normal now.

however she has a RMS leak :p
shop wants $800. i'm going to use some stopleak for now.

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02-04-09, 05:20 PM
I had an alignment done on that truck about 2 months ago now and talked with the midas guys specifically about the problem of the wheel not returning after right turns. They said they set the caster to nominal position and suggested that it might be the wheel position sensor.

FWIW the sensor for this truck does not have a horseshoe to indicate which way is up. I saw a pic on a different forum of a sensor for the '00 trucks and it clearly had that marking, but the sensor for the '01 has no clear markings.

Next thing that I might look into is idler arm. I'm gonn have to wait for the weather to warm up though before that happens.

02-10-09, 10:03 AM
I know on this body style truck that the idler arm has a zerk at the top that NO ONE ever greases.
Be sure to check that one.
I have actually had a loud noise coming from those for lack of proper lubrication.
Perhaps it is binding?
Yeah, they may have changed the sensor design, probably not even the same company making them now.