How JustAnswer Works:
  • Ask an Expert
    Experts are full of valuable knowledge and are ready to help with any question. Credentials confirmed by a Fortune 500 verification firm.
  • Get a Professional Answer
    Via email, text message, or notification as you wait on our site. Ask follow up questions if you need to.
  • 100% Satisfaction Guarantee
    Rate the answer you receive.
Ask Cat Man Your Own Question
Cat Man
Cat Man, Cat Engine Expert
Category: Medium and Heavy Trucks
Satisfied Customers: 8958
Experience:  I am ASE Master Truck Certified.
Type Your Medium and Heavy Trucks Question Here...
Cat Man is online now
A new question is answered every 9 seconds

I have a 2001 gmc 6500 with the 3126 cat engine ifor a flat

Customer Question

I have a 2001 gmc 6500 with the 3126 cat engine ifor a flat bed tow truck and over the last 5 years at times the high idle shuts off on it's own. sometimes it will do right away sometimes when we move the bed. when it happens it you can turn it back on and it will stay on and sometimes when you turn it back on it shuts the high idle off right away. at first i thought moving the automatic shift lever helped and replaced the prindle switch and then it seemed like if i moved the brake pedal it helped so i adjusted the switch and twice have replaced the brake switch. non of that that seemed to help. some times it won't act for weeks.
JA: Sometimes things that you think will be really complicated end up being easy to fix. The Heavy Truck Mechanic I'm going to connect you with knows all the tricks and shortcuts.
Customer: THANK YOU
JA: Anything else you want the truck mechanic to know before I connect you?
Submitted: 2 months ago.
Category: Medium and Heavy Trucks
Expert:  Cat Man replied 2 months ago.
Thanks for asking your question. I will try and help you out.
There are only 4 things that can cause the high idle to disengage.
A clutch switch
A brake switch
A high idle switch
A transmission neutral safety switchIt can either be a faulty switch or faulty wiring to the switch. The engine ecm records which of these cause the kick out of the high idle. To confirm which circuit caused it, I like to connect cat ET and monitor these items.Please reply back if you need more help or have more questions. I am happy to assist.