{"id":403,"date":"2011-03-13T19:08:06","date_gmt":"2011-03-13T23:08:06","guid":{"rendered":"http:\/\/www.tenfourmagazine.com\/content\/?p=403"},"modified":"2011-03-31T20:12:14","modified_gmt":"2011-04-01T00:12:14","slug":"understanding-your-ecm","status":"publish","type":"post","link":"https:\/\/www.tenfourmagazine.com\/content\/2011\/03\/performance-zone\/understanding-your-ecm\/","title":{"rendered":"Understanding Your ECM"},"content":{"rendered":"

\"\"<\/a>It\u2019s been 19 years since the first computer-controlled electronic diesel engine for semi trucks has been released.\u00a0 These days, just about everything on the engine is monitored and controlled by the engine computer, also commonly referred to as the ECU (Electronic Control Unit) or ECM (Electronic Control Module).\u00a0 And each year, these electronics become more and more integrated in the truck.\u00a0 Just being good with a wrench doesn\u2019t cut it anymore.\u00a0 Today\u2019s technicians need to truly understand the electronics and the ECM.<\/p>\n

Think of your truck\u2019s ECM and its electrical system being similar in function to your body\u2019s electrochemical nervous system.\u00a0 The ECM is the brain and can \u201cfeel\u201d problems through its wires and nerve-like sensors.\u00a0 If sensors are the ECM\u2019s nerves, then solenoids (including injector solenoids) can be thought of as the \u201cmuscles\u201d that the ECM controls.\u00a0 Sensors are designed to produce a specific range of either electrical resistance or voltage that changes with temperature, pressure or in the presence of an electromagnetic field.\u00a0 Each sensor typically makes a single signal circuit that feeds into a pin on the ECM.\u00a0 The ECM powers the sensor through a sensor supply and sometimes a sensor return circuit, and then monitors the sensor signal wire by watching the voltage range the sensor sends back.\u00a0 If the voltage drops too low or goes too high, the ECM will let you know by turning on a warning light.\u00a0 The ECM will tell you where to look by giving you a code that identifies a specific circuit and condition.\u00a0 Your brain does this as well, and will quickly let you know if you\u2019re touching something that\u2019s outside of your comfort range \u2013 like a hot exhaust stack.<\/p>\n

Compared to your nervous system, an ECM is very dumb.\u00a0 Most ECMs have no way to verify what the truck is actually doing.\u00a0 The ECM is simply reading a voltage and making an assumption.\u00a0 Because of this, ECMs are easily fooled.\u00a0 I once had an ECM tell me it was reading a turbo compressor outlet temperature of 1,600 degrees \u2013 while at idle!\u00a0 Remember, the ECM is just a machine.\u00a0 It didn\u2019t actually know that the temperature was actually 1,600 degrees \u2013 it was only going by what voltage it received from what it thinks was its temperature sensor.\u00a0 When ECMs do crazy things, like read 1,600 degrees at idle, don\u2019t assume the ECM is bad.\u00a0 There is a big difference between an ECM that is bad and an ECM that is simply being fooled.\u00a0 The ECM that is being fooled is doing its job correctly.\u00a0 What is not working correctly, in this case, is the electrical circuit or sensor the ECM is monitoring.<\/p>\n

Among technicians in the trucking industry, the most widely misunderstood part of the truck is the ECM.\u00a0 As a result, the ECM has become a scapegoat for almost any problem the technician fails to identify.\u00a0 A mechanical problem that a technician fails to recognize (or recognizes but fails to fix properly) is often blamed on the ECM.\u00a0 I have had people blame the ECM for everything from bad valve timing to CB radio interference.\u00a0 Here is a hint: if there isn\u2019t an electrical solenoid or sensor involved with the system having the problem, then the ECM has no control over that system and you\u2019re barking up the wrong tree!<\/p>\n

From time to time, ECMs do fail.\u00a0 ECMs have a limited lifespan.\u00a0 All ECMs have some sort of flash memory and, over the years, this memory will deteriorate and ECM-related circuits on the truck will fail.\u00a0 Also, some ECMs rely on a battery that powers the memory chip, and when the battery wears out, your ECM will soon fail.\u00a0 Sometimes you will get a \u201ccheck engine light\u201d and sometimes you won\u2019t.\u00a0 However, the ECM will almost never leave you stranded.\u00a0 Once a problem begins to develop, you will have a warning, and then several days of driving time left to get to a shop.\u00a0 These batteries usually last about 10 to 12 years, but we recently had a 2005 Cat Acert in the shop and the ECM had failed.\u00a0 So, occasionally, they will fail before their time.\u00a0 This ECM was only six years old and needed to be replaced.\u00a0 Reprogramming an ECM that is about to fail or has other hardware problems is not the answer \u2013 it will not fix the issues.<\/p>\n

In the trucking industry, technicians tend to take shortcuts when working on electrical problems.\u00a0 Instead of tracking down the source of the problem, many mechanics just start making assumptions and changing parts.\u00a0 It doesn\u2019t matter whether the technician doesn\u2019t understand how to diagnose an electrical problem or is just too lazy to do it \u2013 you are the one who\u2019s buying the parts, so their assumptions end up costing you.\u00a0 These guys will typically tell you that the ECM, a sensor, a wiring harness or even an injector is faulty without bothering to test the part and verify that it has actually failed.\u00a0 These parts are expensive, and the technician telling you to replace these parts isn\u2019t buying them \u2013 you are \u2013 so beware of any technician that doesn\u2019t have a well-used multi meter sitting in his toolbox.<\/p>\n

Electrical problems are not always easy to find \u2013 especially if they are intermittent.\u00a0 Some problems only show symptoms under a load, at a specific rpm or when it\u2019s cold outside.\u00a0 Most intermittent electrical problems come and go with no observable reason at all.\u00a0 Thankfully, if your ECM does produce a \u201ccheck engine light\u201d it will log which circuit produced the problem, then you can find it.\u00a0 If a wire is severed or a sensor fails, the ECM only knows it\u2019s getting zero volts back from the sensor.\u00a0 You may just have a dirty, loose, corroded, wet or filled with oil connector.\u00a0 To find out, you have to ohm out the circuit to find the break with a good old-fashioned multi meter.\u00a0 Diagnostic software won\u2019t do this for you \u2013 a multi meter is the only way to be sure.<\/p>\n

The relative simplicity of our Pittsburgh Power Computer allows us to diagnose some problems over the phone, but that is where it stops.\u00a0 These problems are very difficult to find unless you have good diagnostic software and a multi meter.\u00a0 We get many phone calls about electrical problems but we will not attempt to diagnose an electrical problem over the phone.\u00a0 Phone calls like this only make both of us frustrated.\u00a0 You must take your truck to a good shop that is competent with electronics.\u00a0 If you have any comments or questions, I can be reached at Pittsburgh Power in Saxonburg, PA at (724) 360-4080 or by sending an e-mail to bruce@pittsburghpower.com<\/a>.<\/p>\n","protected":false},"excerpt":{"rendered":"

It\u2019s been 19 years since the first computer-controlled electronic diesel engine for semi trucks has been released.\u00a0 These days, just about everything on the engine is monitored and controlled by the engine computer, also commonly referred to as the ECU (Electronic Control Unit) or ECM (Electronic Control Module).\u00a0 And each year, these electronics become more<\/p>\n","protected":false},"author":9,"featured_media":404,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_monsterinsights_skip_tracking":false,"_monsterinsights_sitenote_active":false,"_monsterinsights_sitenote_note":"","_monsterinsights_sitenote_category":0,"ngg_post_thumbnail":0,"footnotes":""},"categories":[6],"tags":[],"class_list":{"0":"post-403","1":"post","2":"type-post","3":"status-publish","4":"format-standard","5":"has-post-thumbnail","7":"category-performance-zone"},"_links":{"self":[{"href":"https:\/\/www.tenfourmagazine.com\/content\/wp-json\/wp\/v2\/posts\/403","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.tenfourmagazine.com\/content\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.tenfourmagazine.com\/content\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.tenfourmagazine.com\/content\/wp-json\/wp\/v2\/users\/9"}],"replies":[{"embeddable":true,"href":"https:\/\/www.tenfourmagazine.com\/content\/wp-json\/wp\/v2\/comments?post=403"}],"version-history":[{"count":5,"href":"https:\/\/www.tenfourmagazine.com\/content\/wp-json\/wp\/v2\/posts\/403\/revisions"}],"predecessor-version":[{"id":482,"href":"https:\/\/www.tenfourmagazine.com\/content\/wp-json\/wp\/v2\/posts\/403\/revisions\/482"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.tenfourmagazine.com\/content\/wp-json\/wp\/v2\/media\/404"}],"wp:attachment":[{"href":"https:\/\/www.tenfourmagazine.com\/content\/wp-json\/wp\/v2\/media?parent=403"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.tenfourmagazine.com\/content\/wp-json\/wp\/v2\/categories?post=403"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.tenfourmagazine.com\/content\/wp-json\/wp\/v2\/tags?post=403"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}