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Cat Man
Cat Man, Cat Engine Expert
Category: Medium and Heavy Trucks
Satisfied Customers: 8677
Experience:  I am ASE Master Truck Certified.
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I have a cat c7 engine wont rev over 1500 I found broken

Customer Question

I have a cat c7 engine wont rev over 1500 I found broken wires rubbing on bottom of air filter housing im getting codes 46,39,31,49,51
Submitted: 10 months ago.
Category: Medium and Heavy Trucks
Expert:  Cat Man replied 10 months ago.
Thanks for asking your question. I will try and help you out.
Is the yellow check engine light on when the engine is running?
Customer: replied 10 months ago.
no check engine light
Customer: replied 10 months ago.
engine starts no problem filters where all changed
Expert:  Cat Man replied 10 months ago.
Thanks for the information.
If the yellow engine light is not on. There are no active codes. The codes you listed must be logged and inactive.
I would first suspect a low fuel pressure problem. I've seen this before. The fuel pressure should remain between 65-85 psi at all times.
There are three things that can cause low pressure. The first is clogged fuel filters. Which you have already changed
Second is a faulty fuel pressure regulator on the back of the head.
Lastly is a weak fuel transfer pump located on the back of the heui pump.
Please reply back if you need more help or have more questions. I am happy to assist.
Expert:  Cat Man replied 10 months ago.

Here are the definitions of your codes.

46 is low oil pressure warning. This can cause RPM limiting if the ECM is programmed to derate.

39 is an injection actuation pressure fault. This does not cause RPM limiting.

31 is a loss of vehicle speed signal. This will cause limited RPM

49 is an inlet air heater fault. This can not cause RPM limiting.

51 is low ECM DC power supply. This can not cause RPM limiting.

If by change the fuel pressure is OK, I would next suspect code 31 or 46 may be active and causing your RPM to limited.

Let me know if you need more help. I am happy to assist.

Expert:  Cat Man replied 10 months 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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