{"id":951,"date":"2026-04-12T13:39:16","date_gmt":"2026-04-12T17:39:16","guid":{"rendered":"https:\/\/www.4roadservice.com\/resources\/?page_id=951"},"modified":"2026-04-12T13:39:21","modified_gmt":"2026-04-12T17:39:21","slug":"detroit-diesel-spn-3556-fmi-16-hydrocarbon-dosing-injector-fault","status":"publish","type":"page","link":"https:\/\/www.4roadservice.com\/resources\/detroit-diesel-spn-3556-fmi-16-hydrocarbon-dosing-injector-fault\/","title":{"rendered":"Detroit Diesel SPN 3556 FMI 16 \u2013 Hydrocarbon Dosing Injector Fault"},"content":{"rendered":"\n<p class=\"wp-block-paragraph\"><a href=\"https:\/\/www.4roadservice.com\/resources\/detroit-diesel-fault-codes-dd13-dd15-dd16\/\">\u2190 Back to Detroit Diesel Fault Codes<\/a><\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Detroit Diesel SPN 3556 FMI 16 indicates a fault with the hydrocarbon dosing injector, which is the component responsible for injecting fuel into the exhaust stream to raise temperatures during active DPF regeneration. When this injector fails on DD13, DD15, and DD16 engines the aftertreatment system cannot generate the heat needed to burn off soot and active regeneration cycles will fail to complete.<\/p>\n\n\n\n<h2 class=\"wp-block-heading\">Symptoms<\/h2>\n\n\n\n<ul class=\"wp-block-list\">\n<li>Check engine light on <\/li>\n\n\n\n<li>DPF or regen warning light illuminated <\/li>\n\n\n\n<li>Active regeneration unable to complete <\/li>\n\n\n\n<li>DPF soot load continuing to rise <\/li>\n\n\n\n<li>Engine derate possible as soot accumulates <\/li>\n\n\n\n<li>May appear alongside incomplete regen or soot load codes<\/li>\n<\/ul>\n\n\n\n<h2 class=\"wp-block-heading\">Cause<\/h2>\n\n\n\n<p class=\"wp-block-paragraph\">This code triggers when the ECM detects the hydrocarbon dosing injector is not performing within specification during a regeneration cycle. Common causes include:<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>Clogged or carbon fouled HC dosing injector <\/li>\n\n\n\n<li>Failed HC dosing injector solenoid <\/li>\n\n\n\n<li>HC dosing injector stuck open or closed <\/li>\n\n\n\n<li>Fuel supply issue to the dosing injector <\/li>\n\n\n\n<li>Damaged or corroded injector wiring or connector <\/li>\n\n\n\n<li>HC dosing pump failure reducing fuel pressure to injector <\/li>\n\n\n\n<li>Water or contamination in the HC dosing fuel supply<\/li>\n<\/ul>\n\n\n\n<h2 class=\"wp-block-heading\">Can You Keep Driving?<\/h2>\n\n\n\n<p class=\"wp-block-paragraph\">Limited driving is possible but without a functioning HC dosing injector active regeneration cannot be completed. Soot will continue to accumulate in the DPF leading to progressively more severe fault codes and derate conditions. Address this fault before soot reaches critical levels.<\/p>\n\n\n\n<h2 class=\"wp-block-heading\">Recommended Action<\/h2>\n\n\n\n<p class=\"wp-block-paragraph\">Have the HC dosing injector inspected for carbon fouling or physical damage. Check the injector wiring and connector for corrosion or damage. Test fuel supply pressure to the injector and inspect the HC dosing pump if pressure is low. A clogged injector may be cleanable but replacement is often the most reliable solution.<\/p>\n\n\n\n<div class=\"schema-faq wp-block-yoast-faq-block\"><div class=\"schema-faq-section\" id=\"faq-question-1776015225812\"><strong class=\"schema-faq-question\">What does Detroit Diesel SPN 3556 FMI 16 mean?<\/strong> <p class=\"schema-faq-answer\">It means the hydrocarbon dosing injector that supplies fuel to the exhaust for DPF regeneration is not functioning correctly, preventing active regeneration cycles from completing.<\/p> <\/div> <div class=\"schema-faq-section\" id=\"faq-question-1776015228577\"><strong class=\"schema-faq-question\">What causes SPN 3556 FMI 16?<\/strong> <p class=\"schema-faq-answer\">The most common causes are a clogged or carbon fouled HC dosing injector, a failed injector solenoid, damaged wiring, or a fuel supply problem to the injector.<\/p> <\/div> <div class=\"schema-faq-section\" id=\"faq-question-1776015228153\"><strong class=\"schema-faq-question\">Can I keep driving with SPN 3556 FMI 16?<\/strong> <p class=\"schema-faq-answer\">Short distances may be possible but without active regeneration capability soot will accumulate in the DPF leading to more severe faults and derate conditions.<\/p> <\/div> <div class=\"schema-faq-section\" id=\"faq-question-1776015227816\"><strong class=\"schema-faq-question\">Will SPN 3556 FMI 16 cause a derate?<\/strong> <p class=\"schema-faq-answer\">Not immediately but as soot accumulates due to failed regeneration cycles more severe DPF soot codes will trigger derate conditions.<\/p> <\/div> <div class=\"schema-faq-section\" id=\"faq-question-1776015227376\"><strong class=\"schema-faq-question\">How do I clear SPN 3556 FMI 16?<\/strong> <p class=\"schema-faq-answer\">Inspect clean or replace the HC dosing injector and verify fuel supply and wiring. Once the injector is functioning correctly and a successful active regeneration is completed the code should clear.<\/p> <\/div> <\/div>\n\n\n\n<h2 class=\"wp-block-heading\">Related codes<\/h2>\n\n\n\n<ul class=\"wp-block-list\">\n<li><a href=\"https:\/\/www.4roadservice.com\/resources\/detroit-diesel-spn-3826-fmi-16-dpf-incomplete-regeneration\/\" type=\"link\" id=\"https:\/\/www.4roadservice.com\/resources\/detroit-diesel-spn-3826-fmi-16-dpf-incomplete-regeneration\/\">SPN 3826 FMI 16 <\/a><\/li>\n\n\n\n<li><a href=\"https:\/\/www.4roadservice.com\/resources\/detroit-diesel-spn-3713-fmi-16-dpf-soot-load-high\/\" type=\"link\" id=\"https:\/\/www.4roadservice.com\/resources\/detroit-diesel-spn-3713-fmi-16-dpf-soot-load-high\/\">SPN 3713 FMI 16 <\/a><\/li>\n\n\n\n<li><a href=\"https:\/\/www.4roadservice.com\/resources\/detroit-diesel-spn-3713-fmi-18-dpf-soot-load-critical\/\" type=\"link\" id=\"https:\/\/www.4roadservice.com\/resources\/detroit-diesel-spn-3713-fmi-18-dpf-soot-load-critical\/\">SPN 3713 FMI 18 <\/a><\/li>\n\n\n\n<li><a href=\"https:\/\/www.4roadservice.com\/resources\/detroit-diesel-spn-3719-fmi-0\/\" type=\"link\" id=\"https:\/\/www.4roadservice.com\/resources\/detroit-diesel-spn-3719-fmi-0\/\">SPN 3719 FMI 0 <\/a><\/li>\n\n\n\n<li><a href=\"https:\/\/www.4roadservice.com\/resources\/detroit-diesel-spn-3242-fmi-16-dpf-inlet-temperature-high-meaning-causes-fix\/\" type=\"link\" id=\"https:\/\/www.4roadservice.com\/resources\/detroit-diesel-spn-3242-fmi-16-dpf-inlet-temperature-high-meaning-causes-fix\/\">SPN 3242 FMI 16<\/a><\/li>\n<\/ul>\n\n\n\n<div class=\"wp-block-group\"><div class=\"wp-block-group__inner-container is-layout-constrained wp-block-group-is-layout-constrained\">\n<h2 class=\"wp-block-heading\">Need Immediate Help With This Fault Code?<\/h2>\n<\/div><\/div>\n\n\n\n<p class=\"wp-block-paragraph\">If your engine is derating, losing power, or unable to complete regeneration, don\u2019t risk further damage or costly downtime.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Use 4RoadService to locate mobile truck repair, dealer diagnostics, or emergency roadside assistance near your location.<\/p>\n\n\n\n<div class=\"wp-block-buttons has-off-white-background-color has-background is-content-justification-center is-layout-flex wp-container-core-buttons-is-layout-fe48e5de wp-block-buttons-is-layout-flex\">\n<div class=\"wp-block-button\"><a class=\"wp-block-button__link wp-element-button\" href=\"https:\/\/www.4roadservice.com\/truck-dealers\">Find Truck Repair Near Me<\/a><\/div>\n\n\n\n<div class=\"wp-block-button\"><a class=\"wp-block-button__link has-text-align-center wp-element-button\" href=\"https:\/\/www.4roadservice.com\/truck-repair\">Find Mobile Road Service<\/a><\/div>\n<\/div>\n\n\n\n<h3 class=\"wp-block-heading\">Important Notice<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">The information provided above is for general informational purposes only and should not replace official OEM service procedures. Always consult the manufacturer\u2019s service manual or a qualified diesel technician before performing repairs. Operating a vehicle with active fault codes may result in further damage.<\/p>\n","protected":false},"excerpt":{"rendered":"<p>\u2190 Back to Detroit Diesel Fault Codes Detroit Diesel SPN 3556 FMI 16 indicates a fault with the hydrocarbon dosing injector, which is the component responsible for injecting fuel into the exhaust stream to raise temperatures during active DPF regeneration. When this injector fails on DD13, DD15, and DD16 engines the aftertreatment system cannot generate &hellip; <a href=\"https:\/\/www.4roadservice.com\/resources\/detroit-diesel-spn-3556-fmi-16-hydrocarbon-dosing-injector-fault\/\" class=\"more-link\">Continue reading <span class=\"screen-reader-text\">Detroit Diesel SPN 3556 FMI 16 \u2013 Hydrocarbon Dosing Injector Fault<\/span> <span class=\"meta-nav\">&rarr;<\/span><\/a><\/p>\n","protected":false},"author":4,"featured_media":0,"parent":0,"menu_order":0,"comment_status":"closed","ping_status":"closed","template":"","meta":{"footnotes":""},"class_list":["post-951","page","type-page","status-publish","hentry"],"yoast_head":"<!-- This site is optimized with the Yoast SEO plugin v28.1 - https:\/\/yoast.com\/product\/yoast-seo-wordpress\/ -->\n<title>SPN 3556 FMI 16 \u2013 Hydrocarbon Dosing Injector Fault<\/title>\n<meta name=\"description\" content=\"Detroit Diesel SPN 3556 FMI 16 means the hydrocarbon dosing injector has a fault. 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Learn symptoms, causes, derate risk and how to fix it.\" \/>\n<meta property=\"og:url\" content=\"https:\/\/www.4roadservice.com\/resources\/detroit-diesel-spn-3556-fmi-16-hydrocarbon-dosing-injector-fault\/\" \/>\n<meta property=\"og:site_name\" content=\"4RoadService Resources\" \/>\n<meta property=\"article:publisher\" content=\"https:\/\/www.facebook.com\/4roadservice\" \/>\n<meta property=\"article:modified_time\" content=\"2026-04-12T17:39:21+00:00\" \/>\n<meta property=\"og:image\" content=\"https:\/\/www.4roadservice.com\/resources\/wp-content\/uploads\/2015\/08\/logo-sidebar@2x.png\" \/>\n\t<meta property=\"og:image:width\" content=\"380\" \/>\n\t<meta property=\"og:image:height\" content=\"64\" \/>\n\t<meta property=\"og:image:type\" content=\"image\/png\" \/>\n<meta name=\"twitter:card\" content=\"summary_large_image\" \/>\n<meta name=\"twitter:site\" content=\"@4RoadService\" \/>\n<meta name=\"twitter:label1\" content=\"Est. reading time\" \/>\n\t<meta name=\"twitter:data1\" content=\"3 minutes\" \/>\n<script type=\"application\/ld+json\" class=\"yoast-schema-graph\">{\"@context\":\"https:\\\/\\\/schema.org\",\"@graph\":[{\"@type\":[\"WebPage\",\"FAQPage\"],\"@id\":\"https:\\\/\\\/www.4roadservice.com\\\/resources\\\/detroit-diesel-spn-3556-fmi-16-hydrocarbon-dosing-injector-fault\\\/\",\"url\":\"https:\\\/\\\/www.4roadservice.com\\\/resources\\\/detroit-diesel-spn-3556-fmi-16-hydrocarbon-dosing-injector-fault\\\/\",\"name\":\"SPN 3556 FMI 16 \u2013 Hydrocarbon Dosing Injector Fault\",\"isPartOf\":{\"@id\":\"https:\\\/\\\/www.4roadservice.com\\\/resources\\\/#website\"},\"datePublished\":\"2026-04-12T17:39:16+00:00\",\"dateModified\":\"2026-04-12T17:39:21+00:00\",\"description\":\"Detroit Diesel SPN 3556 FMI 16 means the hydrocarbon dosing injector has a fault. 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Resources for Truck Drivers","publisher":{"@id":"https:\/\/www.4roadservice.com\/resources\/#organization"},"potentialAction":[{"@type":"SearchAction","target":{"@type":"EntryPoint","urlTemplate":"https:\/\/www.4roadservice.com\/resources\/?s={search_term_string}"},"query-input":{"@type":"PropertyValueSpecification","valueRequired":true,"valueName":"search_term_string"}}],"inLanguage":"en-US"},{"@type":"Organization","@id":"https:\/\/www.4roadservice.com\/resources\/#organization","name":"4RoadService.com","url":"https:\/\/www.4roadservice.com\/resources\/","logo":{"@type":"ImageObject","inLanguage":"en-US","@id":"https:\/\/www.4roadservice.com\/resources\/#\/schema\/logo\/image\/","url":"https:\/\/blog.4roadservice.com\/wp-content\/uploads\/2015\/08\/logo-sidebar@2x.png","contentUrl":"https:\/\/blog.4roadservice.com\/wp-content\/uploads\/2015\/08\/logo-sidebar@2x.png","width":380,"height":64,"caption":"4RoadService.com"},"image":{"@id":"https:\/\/www.4roadservice.com\/resources\/#\/schema\/logo\/image\/"},"sameAs":["https:\/\/www.facebook.com\/4roadservice","https:\/\/x.com\/4RoadService"]},{"@type":"Question","@id":"https:\/\/www.4roadservice.com\/resources\/detroit-diesel-spn-3556-fmi-16-hydrocarbon-dosing-injector-fault\/#faq-question-1776015225812","position":1,"url":"https:\/\/www.4roadservice.com\/resources\/detroit-diesel-spn-3556-fmi-16-hydrocarbon-dosing-injector-fault\/#faq-question-1776015225812","name":"What does Detroit Diesel SPN 3556 FMI 16 mean?","answerCount":1,"acceptedAnswer":{"@type":"Answer","text":"It means the hydrocarbon dosing injector that supplies fuel to the exhaust for DPF regeneration is not functioning correctly, preventing active regeneration cycles from completing.","inLanguage":"en-US"},"inLanguage":"en-US"},{"@type":"Question","@id":"https:\/\/www.4roadservice.com\/resources\/detroit-diesel-spn-3556-fmi-16-hydrocarbon-dosing-injector-fault\/#faq-question-1776015228577","position":2,"url":"https:\/\/www.4roadservice.com\/resources\/detroit-diesel-spn-3556-fmi-16-hydrocarbon-dosing-injector-fault\/#faq-question-1776015228577","name":"What causes SPN 3556 FMI 16?","answerCount":1,"acceptedAnswer":{"@type":"Answer","text":"The most common causes are a clogged or carbon fouled HC dosing injector, a failed injector solenoid, damaged wiring, or a fuel supply problem to the injector.","inLanguage":"en-US"},"inLanguage":"en-US"},{"@type":"Question","@id":"https:\/\/www.4roadservice.com\/resources\/detroit-diesel-spn-3556-fmi-16-hydrocarbon-dosing-injector-fault\/#faq-question-1776015228153","position":3,"url":"https:\/\/www.4roadservice.com\/resources\/detroit-diesel-spn-3556-fmi-16-hydrocarbon-dosing-injector-fault\/#faq-question-1776015228153","name":"Can I keep driving with SPN 3556 FMI 16?","answerCount":1,"acceptedAnswer":{"@type":"Answer","text":"Short distances may be possible but without active regeneration capability soot will accumulate in the DPF leading to more severe faults and derate conditions.","inLanguage":"en-US"},"inLanguage":"en-US"},{"@type":"Question","@id":"https:\/\/www.4roadservice.com\/resources\/detroit-diesel-spn-3556-fmi-16-hydrocarbon-dosing-injector-fault\/#faq-question-1776015227816","position":4,"url":"https:\/\/www.4roadservice.com\/resources\/detroit-diesel-spn-3556-fmi-16-hydrocarbon-dosing-injector-fault\/#faq-question-1776015227816","name":"Will SPN 3556 FMI 16 cause a derate?","answerCount":1,"acceptedAnswer":{"@type":"Answer","text":"Not immediately but as soot accumulates due to failed regeneration cycles more severe DPF soot codes will trigger derate conditions.","inLanguage":"en-US"},"inLanguage":"en-US"},{"@type":"Question","@id":"https:\/\/www.4roadservice.com\/resources\/detroit-diesel-spn-3556-fmi-16-hydrocarbon-dosing-injector-fault\/#faq-question-1776015227376","position":5,"url":"https:\/\/www.4roadservice.com\/resources\/detroit-diesel-spn-3556-fmi-16-hydrocarbon-dosing-injector-fault\/#faq-question-1776015227376","name":"How do I clear SPN 3556 FMI 16?","answerCount":1,"acceptedAnswer":{"@type":"Answer","text":"Inspect clean or replace the HC dosing injector and verify fuel supply and wiring. 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