2006 DTS - Electronic Throttle Relearn

[93SixtySpecial]

Hello,

After driving a Buick for a while, I decided to go back to a Caddy. I was performing some maintenance and after I was finished, my idle was not correct. By the way, this is a 2006 DTS vin Y.

It's tough to detect a pattern, but in drive it runs around 1100-1200 RPM without touching the gas. Sometimes if I apply the brake and come to a complete stop, it fixes itself and goes down to around 800ish. After about 3 seconds if I let off the brake, it will creep back up to that 1100-1200 RPM range and start accelerating. I'm not exactly sure of the precise RPM because my code reader is too old for this car. For some reason, it doesn't seem to do this in reverse or I just haven't tested it enough yet.

Today it seemed to be resolved after I left work. I was able to idle around the parking lot and it seemed to idle correctly. As soon as it warmed up to operating temperature, it went back to the fast idle.

The maintenance that I performed were these items: transmission fluid exchange, main serpentine belt replacement, air filter change and throttle body clean.

In the process of cleaning the throttle body, I broke the nipple that comes out of the air intake duct/hose that connects to the hose in the attached picture (it goes from the intake duct to the valve cover). It appears that the part cannot be ordered separately from the intake duct, so I rigged something temporarily. I can guarantee there is no vacuum leak from that area, so that shouldn't be the issue. Unless there was actually some sort of check valve in that piece that broke, but I couldn't see anything.

I have tried the throttle relearn procedure that I have seen across the web where you turn the key on (with a cold engine) for 3 minutes, turn it off, start it for 30 seconds, and then turn it off and restart. This didn't seem to do anything with the idle. I tried disconnecting the battery for 30 minutes with no luck either. I tried cleaning the throttle body again, thinking I may have not cleaned it enough. Still nothing.

Before this, the car idled perfect. I'm kind of at a loss here. There are no check engine lights whatsoever. Any suggestions are welcome!

[KHE]

What is the condition of the rubber coupler between the intake and the throttle body? If there is a tear on the underside (where they always split) you have a vacum leak which will result in a high idle.

[rockfangd]

Did you touch anything with the throttle body?

If you did it must be relearned, Possibly replaced and relearned.

Otherwise it will very likely idle high and a check engine light should be on. I would be concerned if it is not

[James Woods]

Sounds like a problem with unmetered air (vacuum leak).

One time my wife's car had a high idle even while in gear. I checked everything. Codes vacuum leaks, I double checked everything. Ended up being user error, the floor mat had come free from the retaining hook and was bunched up around the pedal not letting the pedal go back to zero position. I can laugh now, but after hours of diagnosing it wasn't funny then

[airmike]

Sounds like a vacuum leak to me. Have you tried spraying carburetor cleaner around all possible leaks?

[93SixtySpecial]

​I just checked the outside of the coupler this morning of the rubber coupler, but I'll thoroughly check it tonight when the engine cools down a bit.

Yep, I did a throttle body clean. This is at least the 3rd electronic throttle I have cleaned on multiple GMs, but this is the only one I've had an issue afterwards (could be a vacuum leak like everyone including myself is suspecting). No check engine lights though.

I will check the floor mat! At least that would be an easy fix.

I haven't tried carb cleaner yet, but I was going to tonight after I check the coupler.

Does anyone have any idea why it would not have high idle when the brake is applied? Is it because of the vacuum boost for the brakes?

Thanks everyone for the tips. I will post back with my results later tonight.

[rockfangd]

It would be funny if it was the mat on the pedal

It started right after you cleaned the Throttle body right?

If it did it makes me wonder if you removed it or cleaned just the throat and butterfly, Which could cause it to need to be relearned.

The couplers can look good but be bad. Usually are bad at the bottom

[93SixtySpecial]

Sorry for not posting last night. It got a little late.

No mat stuck under the pedal, so we're good there!

It did start right after I cleaned the throttle body, but I also had changed tranny fluid, replaced air filter, replaced serpentine belt, and broke the nipple off of the air duct. It's definitely possible it might still need a relearn. Is there a way to do it myself or do you have to have the PCM reset?

I first visually inspected the coupler with a mirror and it appeared fine. I went around to all the areas where there could be a vacuum leak (PCV hoses and ports, plenum coupler, air intake, air duct, throttle body, purge valve, EGR, etc) and I did not notice any change in RPM during this procedure. I was wanting to find a vacuum leak, so I used plenty of carb cleaner. I made sure to clean up after since I don't know what it does to wires and rubber if it sits on it. I'm assuming that stuff is fairly corrosive.

I'm going to go back to this nipple/port in the air duct that I broke for now. It's the only thing that isn't back to the same after I worked on it. Is there a chance that it's pulling too much air, possibly from the engine, through this port? I may have made the hole a little too big or did something else to mess with it, but I don't know what it looked like before. I can't find any images on the internet.

Would anyone with a 2006 DTS or around that year be willing to take pictures of their air duct so I can compare? I'm most interested in the size of the port inside the air intake.

What would be the symptoms of additional air getting in past the MAF?

[BodybyFisher]

If there is unmetered air should he be getting lean codes?

I dont know the 2006, but when I have cleaned my throttle body she idled fast until the ISC readjusted.

How was the throttle body cleaned, in place or did you remove it?

If the 2006 has an idle speed control is it possible that the connector was dislodged? That however should set a code

If its not setting a code it sounds to me like the plate is not closing. Sometimes the back of the plate has gunk that is loosened and if not cleaned off holds the plate open slightly.

Did you remove the idle speed control / compensator? Is this throttle body throttle by wire?, i.e. no linkage?

When cleaning the throttle plate did you pay attention to the back and edges of the plate and where it contacts the throat? Could something be holding it open, I see you say it drops sometimes when you brake.

Is it possible for the throttle relearn to not take affect? Check all connections around throttle body, electrical and vacuum. But, again unmetered air should set lean code. Sounds mechanical to me, something holding plate open.

Unmetered air and excessively high idle should set a code. If you are 1200 in drive in neutral she must be screaming and the screaming high idle should set a code. Why no codes?

[93SixtySpecial]

​I would think I would get a lean code, but maybe it's not enough to throw a light? Also, I did verify that my check engine light is not burnt out if anyone was curious. I think I'm going to invest in a code reader that can actually read this car. I sure do miss onboard diagnostics.

I don't believe it has an ISC since it's electronic throttle. I made sure that the back and edges were cleaned thoroughly and made sure it moved freely when I was finished (both times). I cleaned it in place and cleaned it with a rag and some O2 sensor safe carb cleaner. I only cleaned as far as I could reach with my hand.

It drops every time I come to a stop with the brake on. About 2-3 seconds after letting off the brake, it will rev up to 1100-1200 RPM again.

I have triple checked all connections around the throttle body and they all seem good.

Sometimes, if I go from drive to park when it's idling high, it will rev up to 1500+ RPM. Other times, it stays around the 1200 mark. When I first start it, it idles normally. It's only when I put it in drive that the high idle situation starts.

I'm going to order an intake duct since the port is broken on it anyway and I want to get rid of my rigged setup that I currently have.

It seems my mileage is suffering with this high idle situation as well, but it's tough to tell since I just bought the car a week before I started the maintenance on it. I didn't have a good idea on what mileage it gets to begin with.

[BodybyFisher]

Lots of interesting hints in your post.. like, it idles fine, until, you put it in drive, hmmm....

For the hell of it, check the plastic L-shaped vacuum connector at the brake booster for a partial crack..that opens on engine shifting

A look at all codes would be terrific maybe the fly by wire is considered a B code? I GOTTA buy a Tech 2, pronto

Its obviously something that happened when you cleaned it. Cant help but thing its related to the relearn.

[93SixtySpecial]

On Tuesday the car started idling normally. Every time I tested it, it wouldn't start accelerating like before. I'm assuming at this point that it was the throttle that needed to be relearned and it did so after some time.

I'm also noticing that when I let off the gas on the highway, the instant economy is now going to 70MPG again. After my idle problem, it wouldn't go much higher than 40-50 MPG when slowing. It appears my mileage is getting better too (around 30 going 60).

I just received my replacement air duct as well. I don't believe that was the cause or even added to the situation as the hole that I created was approximately the same size as the stock one.

I'll update in a few days, but it appears everything is working correctly!

On a side note, does anyone know if there is a way to adjust the tension on the gas pedal? I'm struggling with the ease of pressing the gas pedal and it's causing me to speed or accelerate more than I'd like to. I'm hoping since this is ETC that there might be some adjustment.

[rockfangd]

not to my knowledge . If you get used to it you likely wont even notice

[93SixtySpecial]

I spoke too soon. It's still acting strange, but it's not as bad as it has been before.

I noticed something interesting while doing a few wide open throttle runs. When I took my foot off the throttle, it was slowing down, but VERY slowly. It would almost hold the speed at 70 and it almost sounded like the throttle was still open slightly. Then after a few seconds, it drastically changed and slowed down much quicker (what I would think would be more normal). It did this fairly consistently throughout the procedure. I wouldn't think this is normal, but this is a slightly different beast compared to my 04 DTS.

I'm thinking I may need to go to the dealer to get the throttle relearned/PCM flashed to stock. That's about my only go to at this point. I miss having a cable in between my foot and the throttle.

[rockfangd]

I agree. Likely needs a relearn or replacement. I know GM had bulletin for them but not sure about cadillac

[93SixtySpecial]

Interesting. What was the bulletin for?

I was reading online that there is a stepper motor inside that may have gotten damaged. I wasn't very forceful when opening the throttle plate, so I'm hoping that's not the issue.

It's very odd because some days it seems perfectly fine, some days it's idling semi fast, and others it has a mix. I'm going to try disconnecting the battery for at least an hour and try re-cleaning it with a toothbrush to make sure I really get in there. Then I'm going to try a few different relearn procedures I found. I found an article that said there were 6 different types of relearn procedures that GM has, but I've only found about two

[BodybyFisher]

I worked on a BMW 850i I few years ago that had a bad accelerator, they use opposing voltages as a reference as the accelerator is pressed, zero to 5 volts and 5 to zero volts, with the combined voltage always being 5 volts, if at any point in the accelerator swing the voltage does not equal 5 volts the system went into safe mode. Replaced the accelerator and had a hell of a time doing the relearn, eventually it was taken to the dealer who had the proper bmw "tech 2" type device to do the relearn.

[rockfangd]

IIRC you are not supposed to manually manipulate the butterfly of the throttle body. They are very sensitively calibrated. you likely need a new unit.

I have dealt with these before and my best rule of thumb is it if it runs ok dont mess with it. Something as simple as cleaning the throat and messing with the butterfly will completely throw off the calibration.

I cleaned the TB in my 05 Altima and it was a nightmare to relearn the idle. It kept idling high on certain key cycles then others it seemed to be normal.

But usually while driving it seemed to rev up on its own.

All I had done to clean it was wipe the throat and valve with a rag and that was all it took

[Texas Jim]

I spoke too soon. It's still acting strange, but it's not as bad as it has been before.

I noticed something interesting while doing a few wide open throttle runs. When I took my foot off the throttle, it was slowing down, but VERY slowly. It would almost hold the speed at 70 and it almost sounded like the throttle was still open slightly. Then after a few seconds, it drastically changed and slowed down much quicker (what I would think would be more normal). It did this fairly consistently throughout the procedure. I wouldn't think this is normal, but this is a slightly different beast compared to my 04 DTS.

I'm thinking I may need to go to the dealer to get the throttle relearned/PCM flashed to stock. That's about my only go to at this point. I miss having a cable in between my foot and the throttle.

When you do a wide open throttle and then let off, there is a built in 5 second delay before it shuts the fuel off and the goes back to the 70 mpg on deceleration.

This is to minimize driveline shocks in case you had suddenly let off and then jump back to WOT again...

Normal delay is 3 seconds...