I have a 2006 Yukon Denali XL. When I accellerate from a stop, there is a pause for around 4 seconds and then it accellerates hard. A traction assist message appears on the dash during that time. Also, after just having stopped for a traffic light, the brake pedal will pop up against my foot like something mechanical is happening. Could these issues be related to speed sensors at the wheels?
Hesitation upon initial accelleration
- Thread starter vicnation
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Scottydoggs
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best to start off with getting it scanned for abs codes, need a real scanner for that, but its way better then tossing cash and parts at it hoping its fixed.
things it could be, bad ground on the frame under the drivers foot area. or the abs pump module is broken. they are rebuildable even diy if your up to some soldering. it just sucks to remove cause it under the drivers seat off the frame. theres vids but them little torx bolts like to strip out due to being rusty most of the time.
my hoe does the same thing pretty much, if one wheel spins even a little bit the gas pedal goes dead for like 4-5 seconds. im pretty sure its my abs pump module, i found if i just turn off T/C it does not do it. we also have stability traction control. if you push and hold the t/c button for 8 to 10 seconds the dash should tell you stability control is off, or its not working like mine does. so i just push it the one time and off i go.
things it could be, bad ground on the frame under the drivers foot area. or the abs pump module is broken. they are rebuildable even diy if your up to some soldering. it just sucks to remove cause it under the drivers seat off the frame. theres vids but them little torx bolts like to strip out due to being rusty most of the time.
my hoe does the same thing pretty much, if one wheel spins even a little bit the gas pedal goes dead for like 4-5 seconds. im pretty sure its my abs pump module, i found if i just turn off T/C it does not do it. we also have stability traction control. if you push and hold the t/c button for 8 to 10 seconds the dash should tell you stability control is off, or its not working like mine does. so i just push it the one time and off i go.
Scottydoggs
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no codes with abs scanner? your normal scanner only shows P codes. abs codes are U codes, and are stored in a history part that the abs scanner can see. most of the time theres a boat load of codes in history, so you clear history, then drive and when it happens again, re scan and those are the relevant codes to follow up on.
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@Scottydoggs is talking about a quality bi-directional scanner. Not only does it provide you with codes that cheaper unidirectional scanners cannot recognize, it also allows to to actually test various modules on your truck to see if they are performing as they should.
Scottydoggs
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abs scanners are not cheap really. might be best to stop at a shop and ask if they can scan it for ya. dont be surprised if they want to charge you for the scan.
the few times i've need one the garage right across the street from me will just hand me his snap on scanner and let me have at it for free. talk about being lucky there. i have spent a load of money there over the years tho. not like we are pals or nothing lol
the few times i've need one the garage right across the street from me will just hand me his snap on scanner and let me have at it for free. talk about being lucky there. i have spent a load of money there over the years tho. not like we are pals or nothing lol
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A clone Tech 2 will run you about $350-$450, and an Autec will run you about $500. The Autec is probably a better strategic purchase for new models of vehicles.
it should be noted that abs/srs codes almost always self-clear themselves upon a key cycle, if there is a intermittent problem
say when you hit a bump in the road or accelerate/brake, etc
you want to scan for that type of code when the light comes or has come on even briefly before the vehicle is shut off
they are not OBD systems, but are "read/written" thru the obd diagnostic port
if the problem is constant then you have a light on and/or drive-ability issue's and a persistent code (unable to pass-self checking)
otherwise upon a key cycle the code is normally gone
it's also why cheap scanners won't read abs/srs, it requires additional hardware/software which makes it cost more to produce the product
say when you hit a bump in the road or accelerate/brake, etc
you want to scan for that type of code when the light comes or has come on even briefly before the vehicle is shut off
they are not OBD systems, but are "read/written" thru the obd diagnostic port
if the problem is constant then you have a light on and/or drive-ability issue's and a persistent code (unable to pass-self checking)
otherwise upon a key cycle the code is normally gone
it's also why cheap scanners won't read abs/srs, it requires additional hardware/software which makes it cost more to produce the product
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Scottydoggs
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the light may clear on the dash, but that codes stored in history.
that's a maybe... based on numerous reports including my own experiences
obd codes are more likely to be stored as history codes, some times they don't save either.
and amazingly enough, sometimes cleared codes including history codes can be found even after being cleared
I have cleared history codes with the tech2 and months later, they just show up again out of the blue and "not" because the issue occurred again... just ghost in the machine
Scottydoggs
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only abs codes are stored in a history, i know some of your normal scanners on some cars will read abs codes, but they cant clear or see the history of every code thats been set over time.
if a abs code comes back after clearing, its a actual fault. even if its not setting the abs or brake light on.
if the module is shorting it's not going to save anything, that's why I said "maybe" really depends. A lazy or funky sensor could also cause a problem and not set a code. you might commonly see that happen when coming to a stop and just before a full stop the abs activates and pulses the brake pedal, it's doing that because a sensor is not giving correct data but yet is not off enough to trigger a light or throw a code it just thinks a wheel is slipping.
I have seen both of these instances happen more than once.
other people have reported the same, abs light comes on and goes off, maybe random on/off, yet no code stored.
which is why I always tell people to scan while the light is on or before shutting it off after the light has come on
same with the traction control that is another self-checking system in general it only activates with wheel slip (other problems CAN make it error) but, once it see's all is well it's off
Marty_S
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Hold on there, y'all discussing Case 580 backhoe/4in1/extender or automobiles? Some days, particularly Monday, this born blonde get easily confuzed. Yep, I do.
Update: I checked and cleaned the ground wire connections at the frame under the driver's door and took a short test drive. I didn't get far before the front brakes began locking up on their own. I think the ABS is locking them up for some reason and that must be why if felt like the car wasn't accelerating properly. So, I pulled the codes: P0C8B antilock brake code, C0040 RF Wheel sensor circuit malfunction, and C0283 - another antilock brake code. I have a service brake system message and a service stability message.
Does anyone know what this could be? I took the front wheels off and looked for anything that might be wrong with the wheel sensors and I didn't see anything.
Does anyone know what this could be? I took the front wheels off and looked for anything that might be wrong with the wheel sensors and I didn't see anything.
you won't "see" anything wrong unless the harness is disconnected, try swapping the left & right abs sensors and see if the code follows the sensor
I did swap the sensors and the drivers front sensor was then causing a code. I replaced both front sensors and the ABS has stopped grabbing like it did and the codes have not come back. But I still have the acceleration issue. Whenever I step on the gas, half-to-full throttle from a stop, nothing happens. The engine speed stays the same and there's no acceleration. After several seconds, the acceleration returns. Could this be a defective accelerator pedal? Or, could it be a throttle position sensor? I'm not getting any codes.
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