bwjoyner Report post Posted July 5, 2015 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. Share this post Link to post Share on other sites
dickandlois Report post Posted July 5, 2015 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. Share this post Link to post Share on other sites
bwjoyner Report post Posted July 6, 2015 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. Share this post Link to post Share on other sites
dickandlois Report post Posted July 6, 2015 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. Share this post Link to post Share on other sites
jleamont Report post Posted July 6, 2015 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 Share this post Link to post Share on other sites
bwjoyner Report post Posted July 6, 2015 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. Share this post Link to post Share on other sites
bwjoyner Report post Posted July 9, 2015 Replaced the Injector Activation Sensor today, check engine light is off, codes are gone and engine runs great. Life is GOOD! Share this post Link to post Share on other sites
jleamont Report post Posted July 9, 2015 Good to hear. How hard was it to access on your coach? Share this post Link to post Share on other sites
bwjoyner Report post Posted July 10, 2015 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. Share this post Link to post Share on other sites
jleamont Report post Posted July 10, 2015 Good to hear, with the different floor plans sometimes it can be tough. Nice looking coach also. Safe travels! Share this post Link to post Share on other sites
homefreefmca Report post Posted November 20, 2017 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 Share this post Link to post Share on other sites
wolfe10 Report post Posted November 20, 2017 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? Share this post Link to post Share on other sites
rsbilledwards Report post Posted November 22, 2017 Hate it when the OP's do not follow up...why spend the effort is one does not follow up...??????? Share this post Link to post Share on other sites
manholt Report post Posted November 24, 2017 BillE. Probably tied up for thanksgiving, if nothing from OP next week, then I will agree with you! Who knows, he might be a pilot... Share this post Link to post Share on other sites
dickandlois Report post Posted November 24, 2017 Carl, Think that Homefree lives in Canada, and stays in the Southwest during the winter. So he might be on the road towards a warmer spot. Rich. Share this post Link to post Share on other sites
manholt Report post Posted November 24, 2017 Rich, you maybe on to it...Triple E is the company from Canada that bought out Landau in 1974...very popular in Canada! Share this post Link to post Share on other sites
