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Cat Man
Cat Man, Cat Engine Expert
Category: Medium and Heavy Trucks
Satisfied Customers: 8412
Experience:  I am ASE Master Truck Certified.
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HOW DO YOU GET DIAGNOSTICS OUT OF MY 1998 CHEVY CAT 3126 ENGINE WITHOUT A SCAN TOOL and WH

Customer Question

HOW DO YOU GET DIAGNOSTICS OUT OF MY 1998 CHEVY CAT 3126 ENGINE WITHOUT A SCAN TOOL and WHAT THE CODE MEANS
Submitted: 1 year ago.
Category: Medium and Heavy Trucks
Expert:  Cat Man replied 1 year ago.
Hi. Thanks for asking your question! I will try and help you out.
Use the following procedure to retrieve the flash codes from the check engine light:
Turn the ignition key switch to the On position/ Engine OFF.
Turn the cruise control ON/OFF switch to the OFF position.
Move the SET/RESUME switch to either position. Hold that position until the yellow lamp begins to flash.
The yellow lamp will flash in order to indicate a two digit flash code and the SET/RESUME switch may be released. The sequence of flashes represents the system diagnostic message. Count the first sequence of flashes in order to determine the first digit of the flash code. After a two second pause, the second sequence of flashes will identify the second digit of the flash code.
Any additional flash codes will follow after a pause. These codes will be displayed in the same manner. Flash Code 55 indicates that No Detected Faults have occurred since the ignition key switch has been turned to the ON position.
Let me know what two digit code you get and I can tell you what the problem is.
Customer: replied 1 year ago.
went through the process and it doesn't work no flashing lite
Expert:  Cat Man replied 1 year ago.
I see. Thanks for the information.
I have seen the procedure not work sometimes. Not sure why.
Does the yellow engine light come on at all? Like when you turn the key to the on position?
Also, what kind of problem are you having? Will the engine not start?
Customer: replied 1 year ago.
Yellow lite comes on. Key on engine off starts. Once engine starts lite goes out
Just finished a tow and 2000 rpm is top on level and going up hill normally 45 and now 25. Going up the hill did warm up to 210
Feels like fuel shut off or governor, don't know
Changed fuel filter and water filter and there was a small amount of water in 1st filter, Pulled filter again and no more water
Expert:  Cat Man replied 1 year ago.
Thanks for the information.
So the engine light is not on while driving and the engine has low power?
Customer: replied 1 year ago.
yes
Expert:  Cat Man replied 1 year ago.
Thanks for the information.
Since the check engine light does not come on, I would suspect 1 of 2 things are causing your problem.
The first is low fuel pressure. If there is a low fuel pressure problem, the check engine light will not come on and the engine will have low power. Your engine should maintain a fuel pressure between 65 and 85 psi. There is a plug beside of the secondary fuel filter that is used to check the pressure. If it is low, I would first try the fuel filters if you haven’t already. If it is still low, you may have a failed fuel pressure regulator, which is located on the back of the cylinder head. I have replaced a ton of these for low fuel pressure. It is kinda a known problem. You could also have a weak fuel transfer pump or restricted hand primer pump, if your engine has one.
Second I would suspect you have a low boost condition. This can be caused by a leak in the air piping or air to air aftercooler on the truck. I would first inspect all of the piping to see if there is a hole in any of the rubber boots that hold the pipes. From there you may want to cap off one side of the air to air cooler, and pressurize it. They have been known to crack and leak and cause low boost.
Please let me know if you need more help or have more questions.
Expert:  Cat Man replied 1 year ago.
Hey. I just wanted to see how things were going. Please let me know if you need more help. I am happy to assist. If my information was helpful, please leave a good or higher rating so that I receive credit. Thanks!

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