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Cat Man
Cat Man, Cat Engine Expert
Category: Medium and Heavy Trucks
Satisfied Customers: 8913
Experience:  I am ASE Master Truck Certified.
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I have an 04 peterbilt throwing codes 34 73 72 74 and 34 if

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I have an '04 peterbilt throwing codes 34 73 72 74 and 34 if I've understood how to retrieve the codes correctly... can somebody tell me what they mean?

Hi. Thanks for using JA! I will try and help you out.

 

Code 34 is an engine speed timing sensor fault code.

 

Code 72 is a fault with the injector circuits on cylinders 1 and 2

 

Code 73 is a fault with the injector circuits on cylinders 3 and 4

 

Code 74 is a fault with the injector circuits on cylinders 5 and 6.

 

Please let me know if you need more help or have more questions.

Customer: replied 5 years ago.
do you know how to fix it?

Yes.

 

How is the engine running?

 

Is it a crank no start?

 

Does it run rough and the check engine light on?

Customer: replied 5 years ago.
runs fine, but when cruising will blubber and turns on check engine light

I see. Thanks for the information.

 

You most likely have an engine speed timing sensor problem. I have seen this many times before.

 

Normally when you have fault codes for all the injectors, the engine does not run or run well. this normally indicates the injector driver in the ECM is faulty and the ECM must be replaced.

 

However, since your engine runs fine and just blubbers, I am sure you have an engine speed timing sensor problem. Your engine has 2 engine speed timing sensors. One on the crankshaft and one on the camshaft. the flash code 34 will come up whenever one of them are faulty. You would need to have a service tool like Cat ET connected to read the code and find out which of the two are the problem. Once you find out which one, I would replace the sensor.

 

Please let me know if you need more help or have more questions.

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