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BOBBYSS
BOBBYSS, Master Technician
Category: Chevy
Satisfied Customers: 17368
Experience:  ASE MASTER CERTIFIED, AA DEGREE AUTO/DIESEL TECH
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I have two questions on my 1999 K2500 5.7L It has a severe

Customer Question

I have two questions on my 1999 K2500 5.7L
It has a severe intermitent stutter/hesitation when "cold" on some mornings well until its warmed up then it just goes away???
The other problem (and i don't think they are related at all) is with the brakes and to be more specific the ABS brakes, The brakes do stop this truck just not real good and when i get to the end of the stop (the last 10 feet) the pedal buzzes/vibrates and pushes back and it feels like the front tires are sliding on ice. No lights or CEL on the dash are "ON"
Submitted: 1 year ago.
Category: Chevy
Expert:  BOBBYSS replied 1 year ago.

Hello, my name is Bobby. Thank you for the question. Can you tell me if the truck is all stock? How many miles are on it?

Customer: replied 1 year ago.
Hi, yes its all stock and just over 200,000miles
Expert:  BOBBYSS replied 1 year ago.

Thank you. Most of the time if this hesitation happens when it is cold it is due to a failure in the coolant temperature sensor or a failing air flow sensor. Both of these are common and will cause this on your vehicle. As for the brakes, it sounds like the ABS is kicking in at this low speed. Most of the time this is caused by a failing front wheel speed sensor. If you have an odd tire size on the front or if all of the tires on the truck do not match then this will occur. If the tires are fine then it is more than likely a bad sensor.

Customer: replied 1 year ago.
K, is there a simple voltage or resistance test so i don't replace what i dont have too?
Expert:  BOBBYSS replied 1 year ago.

Unfortunately the only test you can do that is a real true test would be with a computer scan tool that reads this engine and ABS data. You would need to monitor the wheel speed signals as well as the coolant temperature and the air flow reading. If you do not have one with this capability then you can do a voltage test of the front speed sensors, but it will only allow you to see an initial voltage reading.

Customer: replied 1 year ago.
Is it a specific scan tool? I have a digital DVOM
Customer: replied 1 year ago.
Why doesn't the light come on in the dash, i did check for codes but there were none
Expert:  BOBBYSS replied 1 year ago.

It does not have a specific scan tool, just one that communicates with all of the modules and shows you the sensor signals.

Expert:  BOBBYSS replied 1 year ago.

Typically these two sensors will read incorrectly and it will not cause a check engine light. Low fuel pressure would not cause a check engine light also.

Customer: replied 1 year ago.
I have only used the scan tool with the koeo
Expert:  BOBBYSS replied 1 year ago.

Does the scan tool read engine data or just codes?

Customer: replied 1 year ago.
Not sure, i will try it tomorrow but not sure if i can read it if it does. Can i check back with you tomorrow?
Expert:  BOBBYSS replied 1 year ago.

No problem. Let me know when you get a chance. If I am not online when you return give me some time to respond. Thank you and have a great night.

Customer: replied 1 year ago.
Sure and Thank you!
Expert:  BOBBYSS replied 1 year ago.

Thanks.

Customer: replied 1 year ago.
Well i plug in my scan tool and it says it cant id the pcm
??
Expert:  BOBBYSS replied 1 year ago.

If you cannot see this information it will be hard to diagnose. If it cannot ID it then it cannot communicate with it. You might want to try another scanner. Most auto parts stores will scan computers for free and give you the codes.

Customer: replied 1 year ago.
Do you think I should "wing it" and get the temperature sensor and air flow sensor just because and also have the store try to read the codes?
Expert:  BOBBYSS replied 1 year ago.

I would remove the air flow sensor and clean it. Using mass air flow sensor spray cleaner you can spray it out. I would also replace the coolant sensor as that is fairly inexpensive.

Customer: replied 1 year ago.
Why do u think the pcm doesn't communicate?
Expert:  BOBBYSS replied 1 year ago.

It depends on if it is the scan tool or the PCM. If it is the PCM then it may be failing or you may have a bad fuse. I would check the fuses in the fuse box under the hood. Pay close attention to the lighter fuse.

Customer: replied 1 year ago.
I need a coolant sensor and a air flow sensor. Was there something else? Oh and what are the brake sensors called?
Expert:  BOBBYSS replied 1 year ago.

They are called the wheel speed sensors. I hate to see you just replace parts without knowing for sure that they are bad

Customer: replied 1 year ago.
Right, i dont want to do that either.
But i dont know how to test them.
Expert:  BOBBYSS replied 1 year ago.

Check your fuses first to see if we can get the PCM to communicate with your scanner first. If we can communicate with the PCM we can get some answers.

Customer: replied 1 year ago.
Ok ill check those and get back to you, thanks jack
Expert:  BOBBYSS replied 1 year ago.

Thank you Jack. Please let me know.

Customer: replied 1 year ago.
Hi Bobbyss, I was reading online that these sensors may just need to be cleaned, Ill try removing them and cleaning them first.
Someone also said these might be recalled?
All the fuses are good, wish i knew how to communicate with that pcm
Customer: replied 1 year ago.
Oh, i did order the coolant sensor and air temp. sensor from Rockauto
Expert:  BOBBYSS replied 1 year ago.

Let me know what happens when you replace them and we can continue as needed.

Customer: replied 1 year ago.
Bobbyss, well I finally changed the wheel speed sensors along with the wheel bearings and I also changed the coolant sensor and air flow sensor. I have only driven it twice since it's all back together and what I've noticed when I hit the brakes initially the rear brakes lock up they seem very touchy now then when I get down the road they seem to be better
Expert:  BOBBYSS replied 1 year ago.

How old are the rear brakes ? Have they been adjusted recently?

Customer: replied 1 year ago.
I checked the rears and they have plenty of shoe lining left I'm not sure how tight they should be adjusted. As i drove down the driveway yesterday and lightly applied the brakes the rears locked up? I did not change this adjustment.

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