BWJoyner

CAT Engine Code 39

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BWJoyner   

I have a 2003 Discovery on a Freightliner chassis with 3126E Caterpillar engine, 42,000 miles. I am getting a Check Engine Code 39 which appears to be an Injection Actuation Pressure Fault. The engine will start, idle and increase RPM at idle but when the transmission is shifted into drive or reverse the engine will not rev, even at full throttle.

We were about 10 miles from home on our last trip and the Check Engine light came on several times but did not stay on, when the light would came on engine would bog felt like it was not getting fuel.

I have replaced the fuel filter, it is a 2 micron single filter system, but that did not fix the problem.

I have read a couple of post about the Injector Actuation Sensor needing to be replaced but am not sure if that is my problem.

Any ideas on what the problem is would be appreciated.

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BW,

Not as up to speed regarding Cat engines, but look under the dash and see if there are 2 switches mounted just left of the steering column.

Should your coach be equipped with a self diagnostic system, you use these switches to read the ECM stored fault codes.Is this how you got the code you posted?

Cat 3126 that is giving codes 15 & 39. injector accentuation pressure ... look for chafed or corroded wires in the engine harness between the sensor?

Let the group know if you find these switches.

Rich.

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BWJoyner   

Rich, on the CAT 3126 I used the engine Cruse Control to find the Check Engine codes, that's where I got the code 39. The plug to access the ECM and check the engine codes with a scan tool on this motorhome is at the rear of the coach above the radiator I believe. The ECM is mounted in one of the compartments near the engine on the passenger side.

I'll check the wiring harness tomorrow.

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BW - The way they set up the diagnostic code reading on coaches is set up different from Model year and coach builder. Sounds like you got the information using the cruse control on your coach. You might rerun the test and see if there are any other codes present.

The pattern for the display is generally, one code repeats 3 times then a pause, and a three peat of a second code. The pattern continues until all codes have been displayed. Then the codes are repeated until you exit the test.

This is a time when a scan gauge or other system comes in handy to read fault codes.

Keep the group in the loop!

Rich.

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jleamont   

BWJoyner,

I have attached a photo of what you are looking for on your engine, it should resemble the photo (yours is probably painted the color of the engine assuming it has never been replaced) These are a common failure on the 3126E and C7 CAT with the HEUI fuel system.

Usually they will seep oil into the electrical connector through the sensor and cause a malfunction. If I recall they cost around $150.00 and are located on the passenger side of the engine on top to the left of the valve cover (opposite side of the turbocharger) about 1/4 way down the engine behind the belts, directly across from the oil fill in the valve cover, it is screwed into the cylinder head.

Depending on you engine access it should be fairly simple to inspect/change, depending on what tools and skill level you have.

You may have to clean or even replace the connector depending how oil soaked it is. CAT did make a connector pigtail kit for the problem.

Good luck

post-39881-0-80121200-1436187058.png

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BWJoyner   

jleamont, thanks for your help. I will have a look at it today. Fortunately Holt Caterpillar in West Sacramento is not to far away, I'll drive down and get one.

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BWJoyner   

The engine compartment in our Discovery is fairly easy to get to, lift the bed, remove 2 sections of the floor and there is full access to the top and sides of the engine. The Injection Activation Sensor is right where you said it was, screwed into the head near the belt/fan end of the engine, very easy to replace. While I have access to the engine I'll go ahead and do the annual maintenance, clean the engine, check all the belts and hoses, lube the fan bearing, exhaust brake and change the oil. We're planning an extended trip in September so we should be good to go.

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jleamont   

Good to hear, with the different floor plans sometimes it can be tough. Nice looking coach also.

Safe travels!

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wolfe10   
1 hour ago, homefreefmca said:

Am looking for  how much it costs  to replace our Cat3126E . we have a 2022 Triple E Signature. Motor only had 122,000 miles. 

Thanks

Replacing the whole motor? What happened to the original motor???

Or what part of it?

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