{"id":883,"date":"2026-03-21T13:44:03","date_gmt":"2026-03-21T17:44:03","guid":{"rendered":"https:\/\/www.4roadservice.com\/resources\/?page_id=883"},"modified":"2026-03-21T13:44:03","modified_gmt":"2026-03-21T17:44:03","slug":"detroit-diesel-spn-4374-fmi-18-def-doser-valve-current-low","status":"publish","type":"page","link":"https:\/\/www.4roadservice.com\/resources\/detroit-diesel-spn-4374-fmi-18-def-doser-valve-current-low\/","title":{"rendered":"Detroit Diesel SPN 4374 FMI 18 \u2013 DEF Doser Valve Current Low (Meaning, Causes &amp; Fix)"},"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 4374 FMI 18 indicates that the electrical current to the DEF doser valve is below the expected threshold. This code appears on DD13, DD15, and DD16 engines and points to an electrical fault in the DEF dosing circuit that is preventing the doser valve from operating correctly, which will affect SCR system performance and can lead to a derate condition.<\/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>DEF or SCR warning light illuminated <\/li>\n\n\n\n<li>Engine derate condition possible <\/li>\n\n\n\n<li>DEF dosing system not functioning correctly <\/li>\n\n\n\n<li>May appear alongside other doser valve or DEF system 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 lower than expected current draw from the DEF doser valve circuit. Common causes include:<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>Open circuit in the doser valve wiring harness <\/li>\n\n\n\n<li>Damaged or corroded doser valve connector <\/li>\n\n\n\n<li>Failed doser valve solenoid with low resistance <\/li>\n\n\n\n<li>Broken wire between ECM and doser valve <\/li>\n\n\n\n<li>Water intrusion in the doser valve connector <\/li>\n\n\n\n<li>Faulty ECM output driver for the doser valve circuit<\/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 may be possible but without proper electrical function the DEF doser valve cannot operate correctly and the SCR system will be unable to control DEF delivery. A derate condition is likely if the fault is not resolved promptly.<\/p>\n\n\n\n<h2 class=\"wp-block-heading\">Recommended Action<\/h2>\n\n\n\n<p class=\"wp-block-paragraph\">Inspect the DEF doser valve wiring harness and connector for damage, corrosion, or broken wires. Check for water intrusion at the connector. Test the doser valve solenoid resistance against specification. If wiring and connector are intact and the solenoid tests good have the ECM output circuit evaluated by a qualified technician.<\/p>\n\n\n\n<div class=\"schema-faq wp-block-yoast-faq-block\"><div class=\"schema-faq-section\" id=\"faq-question-1774114708202\"><strong class=\"schema-faq-question\"><strong>What does Detroit Diesel SPN 4374 FMI 18 mean?<\/strong><\/strong> <p class=\"schema-faq-answer\">It means the electrical current to the DEF doser valve is below the expected level, indicating an electrical fault in the dosing circuit that prevents proper valve operation.<\/p> <\/div> <div class=\"schema-faq-section\" id=\"faq-question-1774114710678\"><strong class=\"schema-faq-question\"><strong>What causes SPN 4374 FMI 18?<\/strong><\/strong> <p class=\"schema-faq-answer\">The most common causes are an open circuit or broken wire in the doser valve harness, a corroded connector, water intrusion at the connector, or a failed doser valve solenoid.<\/p> <\/div> <div class=\"schema-faq-section\" id=\"faq-question-1774114710271\"><strong class=\"schema-faq-question\">Can I keep driving with SPN 4374 FMI 18?<\/strong> <p class=\"schema-faq-answer\">Short distances may be possible but without correct electrical supply the doser valve cannot function and the SCR system will be compromised, leading to a likely derate condition.<\/p> <\/div> <div class=\"schema-faq-section\" id=\"faq-question-1774114709887\"><strong class=\"schema-faq-question\">Will SPN 4374 FMI 18 cause a derate?<\/strong> <p class=\"schema-faq-answer\">Yes. If the doser valve cannot operate due to low current the SCR system will be unable to deliver DEF correctly and the ECM will trigger a derate condition.<\/p> <\/div> <div class=\"schema-faq-section\" id=\"faq-question-1774114709336\"><strong class=\"schema-faq-question\"><strong>How do I clear SPN 4374 FMI 18?<\/strong><\/strong> <p class=\"schema-faq-answer\">Inspect and repair the doser valve wiring and connector. Test the solenoid and replace the valve if faulty. Once the ECM confirms correct current draw to the doser valve 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-4375-fmi-18-def-doser-valve-response-fault\/\" type=\"link\" id=\"https:\/\/www.4roadservice.com\/resources\/detroit-diesel-spn-4375-fmi-18-def-doser-valve-response-fault\/\">SPN 4375 FMI 18 <\/a><\/li>\n\n\n\n<li><a href=\"https:\/\/www.4roadservice.com\/resources\/detroit-diesel-spn-4076-fmi-18-def-dosing-injector-fault\/\" type=\"link\" id=\"https:\/\/www.4roadservice.com\/resources\/detroit-diesel-spn-4076-fmi-18-def-dosing-injector-fault\/\">SPN 4076 FMI 18 <\/a><\/li>\n\n\n\n<li><a href=\"https:\/\/www.4roadservice.com\/resources\/detroit-diesel-spn-4094-fmi-18-def-dosing-low-flow\/\" type=\"link\" id=\"https:\/\/www.4roadservice.com\/resources\/detroit-diesel-spn-4094-fmi-18-def-dosing-low-flow\/\">SPN 4094 FMI 18 <\/a><\/li>\n\n\n\n<li><a href=\"https:\/\/www.4roadservice.com\/resources\/detroit-diesel-spn-3362-fmi-1-def-pump-pressure-low\/\" type=\"link\" id=\"https:\/\/www.4roadservice.com\/resources\/detroit-diesel-spn-3362-fmi-1-def-pump-pressure-low\/\">SPN 3362 FMI 1<\/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 4374 FMI 18 indicates that the electrical current to the DEF doser valve is below the expected threshold. This code appears on DD13, DD15, and DD16 engines and points to an electrical fault in the DEF dosing circuit that is preventing the doser valve from &hellip; <a href=\"https:\/\/www.4roadservice.com\/resources\/detroit-diesel-spn-4374-fmi-18-def-doser-valve-current-low\/\" class=\"more-link\">Continue reading <span class=\"screen-reader-text\">Detroit Diesel SPN 4374 FMI 18 \u2013 DEF Doser Valve Current Low (Meaning, Causes &amp; Fix)<\/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-883","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>Detroit Diesel SPN 100 FMI 1 \u2013 Oil Pressure Low Fix<\/title>\n<meta name=\"description\" content=\"Detroit Diesel SPN 100 FMI 1 indicates low engine oil pressure. 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Fix)"}]},{"@type":"WebSite","@id":"https:\/\/www.4roadservice.com\/resources\/#website","url":"https:\/\/www.4roadservice.com\/resources\/","name":"4RoadService Resources","description":"Tools, Repairs &amp; 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-4374-fmi-18-def-doser-valve-current-low\/#faq-question-1774114708202","position":1,"url":"https:\/\/www.4roadservice.com\/resources\/detroit-diesel-spn-4374-fmi-18-def-doser-valve-current-low\/#faq-question-1774114708202","name":"What does Detroit Diesel SPN 4374 FMI 18 mean?","answerCount":1,"acceptedAnswer":{"@type":"Answer","text":"It means the electrical current to the DEF doser valve is below the expected level, indicating an electrical fault in the dosing circuit that prevents proper valve operation.","inLanguage":"en-US"},"inLanguage":"en-US"},{"@type":"Question","@id":"https:\/\/www.4roadservice.com\/resources\/detroit-diesel-spn-4374-fmi-18-def-doser-valve-current-low\/#faq-question-1774114710678","position":2,"url":"https:\/\/www.4roadservice.com\/resources\/detroit-diesel-spn-4374-fmi-18-def-doser-valve-current-low\/#faq-question-1774114710678","name":"What causes SPN 4374 FMI 18?","answerCount":1,"acceptedAnswer":{"@type":"Answer","text":"The most common causes are an open circuit or broken wire in the doser valve harness, a corroded connector, water intrusion at the connector, or a failed doser valve solenoid.","inLanguage":"en-US"},"inLanguage":"en-US"},{"@type":"Question","@id":"https:\/\/www.4roadservice.com\/resources\/detroit-diesel-spn-4374-fmi-18-def-doser-valve-current-low\/#faq-question-1774114710271","position":3,"url":"https:\/\/www.4roadservice.com\/resources\/detroit-diesel-spn-4374-fmi-18-def-doser-valve-current-low\/#faq-question-1774114710271","name":"Can I keep driving with SPN 4374 FMI 18?","answerCount":1,"acceptedAnswer":{"@type":"Answer","text":"Short distances may be possible but without correct electrical supply the doser valve cannot function and the SCR system will be compromised, leading to a likely derate condition.","inLanguage":"en-US"},"inLanguage":"en-US"},{"@type":"Question","@id":"https:\/\/www.4roadservice.com\/resources\/detroit-diesel-spn-4374-fmi-18-def-doser-valve-current-low\/#faq-question-1774114709887","position":4,"url":"https:\/\/www.4roadservice.com\/resources\/detroit-diesel-spn-4374-fmi-18-def-doser-valve-current-low\/#faq-question-1774114709887","name":"Will SPN 4374 FMI 18 cause a derate?","answerCount":1,"acceptedAnswer":{"@type":"Answer","text":"Yes. If the doser valve cannot operate due to low current the SCR system will be unable to deliver DEF correctly and the ECM will trigger a derate condition.","inLanguage":"en-US"},"inLanguage":"en-US"},{"@type":"Question","@id":"https:\/\/www.4roadservice.com\/resources\/detroit-diesel-spn-4374-fmi-18-def-doser-valve-current-low\/#faq-question-1774114709336","position":5,"url":"https:\/\/www.4roadservice.com\/resources\/detroit-diesel-spn-4374-fmi-18-def-doser-valve-current-low\/#faq-question-1774114709336","name":"How do I clear SPN 4374 FMI 18?","answerCount":1,"acceptedAnswer":{"@type":"Answer","text":"Inspect and repair the doser valve wiring and connector. Test the solenoid and replace the valve if faulty. 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