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Cat Man
Cat Man, Cat Engine Expert
Category: Medium and Heavy Trucks
Satisfied Customers: 8717
Experience:  I am ASE Master Truck Certified.
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I'm a light duty tech, and I am currently heels in a gmc

Customer Question

I'm a light duty tech, and I am currently heels in a gmc 6500 with a 3126 cat enginr. Initially I was just supposed to do the valve cover gaskets . And now at completion of gaskets I am having low power in all gears but gradually got worse from hight to lower gear within 5or so miles... power steering fluid level was only half full and filthy and had almost 1 gallon of oil more than it should . Damn new guys..lol. obviously hydro boost and or turbo as well . Also I have an electronic engine part that I just don't recognize. Looks like spool valve . Can you receive a photo attachment to confirm part and location of said part .. BTW I'm James. .. thank you
Submitted: 1 year ago.
Category: Medium and Heavy Trucks
Expert:  Cat Man replied 1 year ago.
Hi James. Thanks for asking your question! I will try and help you out.
Yes I can help you with your part. Just upload a pic and I can tell you what it is.
Does the yellow check engine light come on while driving?
Did the engine have low power before the valve cover gasket replacement?
Customer: replied 1 year ago.
the yellow mil light is on and blinks intermittently. Is that the blink code ? FYI the stored dtc was (B116B- LH POWERADE RUNNING BOARD MOTOR. THAT'S ALL THE INFO I COULD FIND ON THAT.
AND yes power has been continuously getting lower from 6th at 50mph to no hydro assistance at all. In emergency on the road last night I of coarse jammed the ac full blast and recovered enough power assist to get back to shop by city streets . But engine fid not want to stay running very well to say the least .
Expert:  Cat Man replied 1 year ago.
Thanks for the information.
Yes that's a code if the light is on.
If the truck has cruise control, we can pull the two digit flash code by using the cruise control switches.
Does the truck have cruise control?
Customer: replied 1 year ago.
it does
Expert:  Cat Man replied 1 year ago.
Here is how to pull the codes.
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.
11
Expert:  Cat Man replied 1 year ago.
Thanks for the information.
Unfortunately there is not a code 11. Sorry. Maybe try it again.
Customer: replied 1 year ago.
Ok going off like Morse code . But I think their as follows .
67 , 47, 37 ,72
Expert:  Cat Man replied 1 year ago.
Thanks for the information.
No codes 37 or 67. Sorry.
Code 47 is an idle shutdown. That does not cause low power.
Code 72 is a faulty with either the number one or number two injector circuit. Cat only gives one code for both 1 and 2.
If one or both of these are not firing. It will cause low power.
Normally I see a code 39 that causes low power. It's very common on these engines. That's a fault with the injection actuation pressure system.
Please reply back if you need more help or have more questions. I am happy to assist.
Customer: replied 1 year ago.
What's the test procedure for 39 47 &72????????
Customer: replied 1 year ago.
Here's the part I need identified . I believe it to be an injector solonoid or spool valve part. ?
Expert:  Cat Man replied 1 year ago.
I would not worry about 47. That's just an idle shut down.
Code 72 needs to have Cat ET software connected to run a solenoid test to verify which is faulty of one or two.
For code 39. This is the high pressure oil system that activates the injectors. The engine needs at least 870 psi to start. If it is low, you have either a failed Injection actuation pressure control valve in the HEUI pump, a weak HEUI pump, a high pressure oil leak at an injector, or a faulty Injection actuation pressure sensor. To test the sensor, just unplug it. If the engine starts, the sensor is bad. It has 3 wires and is located on top of the engine near the front and screwed into the head. To test the HEUI pump. You would need to connect a 5000 psi gauge to the outlet of the pump.
Expert:  Cat Man replied 1 year ago.
I see your part. I have not ever seen that. It's not a Cat engine part for sure.
Please reply back if you need more help or have more questions. I am happy to assist.
Customer: replied 1 year ago.
Are there any special steps to swapping that p reassure sensor
Expert:  Cat Man replied 1 year ago.
No nothing special at all. Just remove and replace. No calibration needed.
Customer: replied 1 year ago.
Last question . Please. This obviously helps build pressure. But should it remain open or does it need to be plugged while running?
Expert:  Cat Man replied 1 year ago.
That's the oil fill. It should be closed at all times.
Please reply back if you need more help or have more questions. I am happy to assist.
Customer: replied 1 year ago.
Oil fill? For what oil ? I thought oil was to be put in thru oil cap at top of fuel injectors cover? Please explain?
Expert:  Cat Man replied 1 year ago.
That is an engine oil fill. Some engines have an oil fill on the front. It should have a twist style cap. I think I see it behind the front cover to the right.
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.
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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