{"id":517966,"date":"2025-12-10T11:58:06","date_gmt":"2025-12-10T16:58:06","guid":{"rendered":"https:\/\/www.fs1inc.com\/blog\/dtc-p1391-glow-plug-circuit-low-input-bank-1\/"},"modified":"2025-12-10T11:58:06","modified_gmt":"2025-12-10T16:58:06","slug":"dtc-p1391-glow-plug-circuit-low-input-bank-1","status":"publish","type":"post","link":"https:\/\/www.fs1inc.com\/blog\/dtc-p1391-glow-plug-circuit-low-input-bank-1\/","title":{"rendered":"P1391 Code Symptoms, Causes, Diagnosis &#038; Repair Guide Step-by-Step"},"content":{"rendered":"<div class=\"container\">\n<section class=\"hero\">\n<div class=\"code-badge\">P1391<\/div>\n<h1>P1391 Code Symptoms, Causes, Diagnosis &amp; Repair Guide Step-by-Step<\/h1>\n<p class=\"hero-subtitle\">\n<\/section>\n<div class=\"quick-summary\">\n<h2>Quick Summary<\/h2>\n<ul>\n<li>P1391 = Glow Plug Circuit Low Input (Bank 1) on diesel engines. <\/li>\n<li>Drivers notice hard starts, prolonged cranking, rough idle, and occasional misfires, especially in cold weather. <\/li>\n<li>Primary causes are wiring\/connector issues, blown fuses or relays, and ECM\/PCM output\u2011stage failures. <\/li>\n<li>Diagnosis starts with a scan, then voltage\/continuity checks and, if needed, module output testing. <\/li>\n<li>Replacement of the ECM\/PCM typically costs $800\u2011$1,200 plus $200\u2011$300 labor; repair of the circuit is $200\u2011$400. <\/li>\n<li>Flagship One supplies VIN\u2011matched, pre\u2011programmed control modules for reliable replacement. <\/li>\n<\/ul>\n<\/div>\n<h3>P1391 Code \u2013 Symptoms, Causes, and How to Fix It <\/h3>\n<p>When the glow\u2011plug circuit on Bank 1 delivers insufficient voltage, the diesel engine struggles to ignite. Drivers usually experience hard\u2011starting conditions, extended cranking times, a rough idle that smooths out as the engine warms, and occasional misfires that are most noticeable in cold weather. The check\u2011engine light flashes, and overall engine power may feel reduced until the circuit voltage returns to normal.<\/p>\n<h2>Symptoms <\/h2>\n<ul>\n<li><strong>Hard starting or failure to start<\/strong> after a cold soak; cranking may last 5 seconds or longer. <\/li>\n<li><strong>Extended cranking<\/strong> with the starter motor running but the engine not firing. <\/li>\n<li><strong>Rough idle<\/strong> for the first few minutes after start\u2011up; idle steadies as the engine reaches operating temperature. <\/li>\n<li><strong>Intermittent misfires<\/strong> on one or more cylinders, typically on the side of Bank 1. <\/li>\n<li><strong>Check\u2011engine light<\/strong> illuminated with the P1391 code stored in the ECM. <\/li>\n<\/ul>\n<p>These signs appear most often in low ambient temperatures because glow plugs are essential for pre\u2011heating the combustion chambers of a diesel engine.<\/p>\n<h2>Why Glow Plug Circuit Problems Occur <\/h2>\n<h3>H3 Wiring and Connector Degradation <\/h3>\n<p>Corrosion, broken strands, or loose pins in the harness that feeds the glow\u2011plug circuit can drop voltage below the ECM\u2019s minimum threshold. Water intrusion from road spray or a leaking head gasket accelerates corrosion, especially on the bank\u20111 connector.<\/p>\n<h3>H3 Fuse or Relay Failure <\/h3>\n<p>The glow\u2011plug circuit is protected by a dedicated fuse (often 10 A) and a relay that switches the high\u2011current path. A partially blown fuse or a relay that fails to close fully reduces the voltage reaching the plugs, triggering the low\u2011input code.<\/p>\n<h3>H3 ECM\/PCM Output\u2011Stage Fault <\/h3>\n<p>The ECM supplies the control voltage to the glow\u2011plug driver circuit. Internal board damage, solder joint cracks, or a software glitch can prevent the module from delivering the required 12 V. When the output stage is compromised, the voltage measured at the plug terminals will be low despite good wiring and fuses.<\/p>\n<h3>H3 Glow\u2011Plug Element Failure <\/h3>\n<p>A severely worn or shorted glow plug presents high resistance, causing the circuit voltage to sag under load. While the plug itself is not a control\u2011module component, its failure often reveals a broader issue with the circuit that the ECM must monitor.<\/p>\n<h3>H3 Battery and Charging\u2011System Voltage Drop <\/h3>\n<p>A weak battery or a charging system that cannot maintain at least 13.5 V under load will starve the glow\u2011plug circuit. The ECM may register a low\u2011input condition and set P1391, even though the wiring and module are sound.<\/p>\n<h2>Diagnostic and Repair Procedures <\/h2>\n<ol>\n<li><strong>Scan for Codes<\/strong> \u2013 Connect a dealer\u2011level scanner, read the P1391 and any related codes (e.g., P1390, P1392). Clear the code and note if it returns after a test drive.\n<\/li>\n<li><strong>Live Data Review<\/strong> \u2013 Observe the glow\u2011plug voltage sensor (if equipped) while cranking. Voltage below 8 V indicates a low\u2011input condition.\n<\/li>\n<li><strong>Fuse and Relay Inspection<\/strong> \u2013 Remove the glow\u2011plug fuse; test for continuity and replace if resistance exceeds 0 \u03a9. Swap the relay with a known good unit to rule out contact wear.\n<\/li>\n<li><strong>Wiring Continuity Test<\/strong> \u2013 Using a multimeter, measure resistance from the ECM output pin to the plug connector on Bank 1. Values above 0.2 \u03a9 suggest corrosion or a broken wire.\n<\/li>\n<li><strong>Connector Cleaning<\/strong> \u2013 Disconnect the bank\u20111 glow\u2011plug connector, spray electrical contact cleaner, and reseat firmly.\n<\/li>\n<li><strong>Glow\u2011Plug Resistance Check<\/strong> \u2013 Remove each plug on Bank 1, measure resistance; values above 2 \u03a9 indicate a plug that should be replaced.\n<\/li>\n<li><strong>ECM Output Verification<\/strong> \u2013 With the engine off, apply 12 V to the ECM\u2019s glow\u2011plug output pin and measure voltage at the plug connector. If the voltage does not appear, the ECM\u2019s driver circuit is at fault.\n<\/li>\n<li><strong>Reprogramming<\/strong> \u2013 If the ECM passes hardware tests, update the module software to the latest version; some manufacturers release calibrations that address low\u2011input detection thresholds.\n<\/li>\n<li><strong>Repair vs. Replace Decision<\/strong> \u2013 If the ECM output stage fails or the module shows water damage, replacement is the most reliable solution.\n<\/li>\n<\/ol>\n<p>Typical repair costs for wiring, fuses, and relay replacement range from $200 to $400, including labor. ECM replacement, including a VIN\u2011matched unit and programming, averages $800\u2011$1,200 for the part plus $200\u2011$300 labor.<\/p>\n<h2>When Replacement Makes Sense <\/h2>\n<div class=\"flagship-logo-section\">\n<a href=\"https:\/\/www.fs1inc.com\/\" rel=\"noopener noreferrer\" target=\"_blank\"><br \/>\n<img decoding=\"async\" alt=\"Flagship One\" class=\"flagship-logo\" src=\"https:\/\/www.fs1inc.com\/blog\/wp-content\/uploads\/2025\/12\/fs1inc_logo2-scaled.jpg\"\/><br \/>\n<\/a>\n<\/div>\n<p>When the ECM\u2019s glow\u2011plug driver circuit is internally damaged, repairs are often temporary. Moisture intrusion, cracked solder joints, or a burned driver transistor can cause recurring low\u2011input readings even after wiring is restored. In such cases, swapping the control module eliminates the root cause and restores reliable operation.<\/p>\n<p>Modern control modules are complex and integrated with security and immobilizer systems. That&#8217;s why choosing a replacement isn&#8217;t only about the hardware\u2014it&#8217;s about correct programming and compatibility. <strong>Flagship One specializes in VIN\u2011matched control modules, providing a plug\u2011and\u2011drive solution backed by warranty.<\/strong> Replacement units vary depending on production date and software version, so the correct module is matched by VIN before programming. This ensures seamless integration with your vehicle\u2019s network and eliminates the need for dealer re\u2011programming delays.<\/p>\n<h2>Preventive Maintenance <\/h2>\n<ul>\n<li><strong>Inspect wiring harnesses<\/strong> for signs of abrasion or corrosion at regular service intervals, especially after winter road\u2011salt exposure. <\/li>\n<li><strong>Clean and tighten connectors<\/strong> on the glow\u2011plug circuit every 12 months; apply dielectric grease to repel moisture. <\/li>\n<li><strong>Replace fuses and relays<\/strong> proactively if they show discoloration or intermittent operation. <\/li>\n<li><strong>Maintain battery health<\/strong>; keep the charge above 12.6 V at rest and verify the alternator output stays above 13.5 V under load. <\/li>\n<li><strong>Follow manufacturer\u2011recommended glow\u2011plug replacement intervals<\/strong> (often every 80,000\u2013120,000 mi) to avoid high\u2011resistance plugs that can stress the circuit. <\/li>\n<li><strong>Use proper engine coolant<\/strong> and ensure the cooling system is sealed to prevent water ingress into the electronic control bay.<\/li>\n<\/ul>\n<p>Adhering to these practices reduces the likelihood of voltage drops that trigger P1391 and extends the life of both the glow\u2011plug circuit and the ECM.<\/p>\n<div class=\"info-section\">\n<p><strong>Service Recommendation:<\/strong> Most issues related to this fault are diagnosed and corrected through inspection, wiring repair, and calibration rather than module replacement. For modules not typically replaced through aftermarket suppliers, diagnosis and repair should be performed by a certified automotive technician with access to factory service information and tooling.<\/p>\n<\/div>\n<\/div>\n","protected":false},"excerpt":{"rendered":"<p>Your diesel won\u2019t start or cranks weak \u2013 P1391 signals low\u2011input glow plug circuit Bank 1. Diagnose wiring or module fault to prevent engine damage.<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"closed","sticky":false,"template":"elementor_header_footer","format":"standard","meta":{"_acf_changed":false,"footnotes":""},"categories":[4],"tags":[],"class_list":["post-517966","post","type-post","status-publish","format-standard","hentry","category-auto-news"],"acf":[],"yoast_head":"<!-- This site is optimized with the Yoast SEO plugin v27.7 - https:\/\/yoast.com\/product\/yoast-seo-wordpress\/ -->\n<title>P1391 Code Symptoms, Causes, Diagnosis &amp; Repair Guide Step-by-Step - Flagship One Blog<\/title>\n<meta name=\"robots\" content=\"index, follow, max-snippet:-1, max-image-preview:large, max-video-preview:-1\" \/>\n<link rel=\"canonical\" href=\"https:\/\/www.fs1inc.com\/blog\/dtc-p1391-glow-plug-circuit-low-input-bank-1\/\" \/>\n<meta property=\"og:locale\" content=\"en_US\" \/>\n<meta property=\"og:type\" content=\"article\" \/>\n<meta property=\"og:title\" content=\"P1391 Code Symptoms, Causes, Diagnosis &amp; Repair Guide Step-by-Step - Flagship One Blog\" \/>\n<meta property=\"og:description\" content=\"Your diesel won\u2019t start or cranks weak \u2013 P1391 signals low\u2011input glow plug circuit Bank 1. Diagnose wiring or module fault to prevent engine damage.\" \/>\n<meta property=\"og:url\" content=\"https:\/\/www.fs1inc.com\/blog\/dtc-p1391-glow-plug-circuit-low-input-bank-1\/\" \/>\n<meta property=\"og:site_name\" content=\"Flagship One Blog\" \/>\n<meta property=\"article:publisher\" content=\"https:\/\/www.facebook.com\/flagshipone\" \/>\n<meta property=\"article:author\" content=\"https:\/\/www.facebook.com\/flagshipone\/\" \/>\n<meta property=\"article:published_time\" content=\"2025-12-10T16:58:06+00:00\" \/>\n<meta property=\"og:image\" content=\"https:\/\/www.fs1inc.com\/blog\/wp-content\/uploads\/2025\/12\/fs1inc_logo2-scaled.jpg\" \/>\n<meta name=\"author\" content=\"FlagshipOne\" \/>\n<meta name=\"twitter:card\" content=\"summary_large_image\" \/>\n<meta name=\"twitter:creator\" content=\"@theflagshipone\" \/>\n<meta name=\"twitter:site\" content=\"@theflagshipone\" \/>\n<meta name=\"twitter:label1\" content=\"Written by\" \/>\n\t<meta name=\"twitter:data1\" content=\"FlagshipOne\" \/>\n\t<meta name=\"twitter:label2\" content=\"Est. reading time\" \/>\n\t<meta name=\"twitter:data2\" content=\"6 minutes\" \/>\n<script type=\"application\/ld+json\" class=\"yoast-schema-graph\">{\"@context\":\"https:\\\/\\\/schema.org\",\"@graph\":[{\"@type\":\"Article\",\"@id\":\"https:\\\/\\\/www.fs1inc.com\\\/blog\\\/dtc-p1391-glow-plug-circuit-low-input-bank-1\\\/#article\",\"isPartOf\":{\"@id\":\"https:\\\/\\\/www.fs1inc.com\\\/blog\\\/dtc-p1391-glow-plug-circuit-low-input-bank-1\\\/\"},\"author\":{\"name\":\"FlagshipOne\",\"@id\":\"https:\\\/\\\/www.fs1inc.com\\\/blog\\\/#\\\/schema\\\/person\\\/a3cf463514bd03eb7656953ef8f75700\"},\"headline\":\"P1391 Code Symptoms, Causes, Diagnosis &#038; Repair Guide Step-by-Step\",\"datePublished\":\"2025-12-10T16:58:06+00:00\",\"mainEntityOfPage\":{\"@id\":\"https:\\\/\\\/www.fs1inc.com\\\/blog\\\/dtc-p1391-glow-plug-circuit-low-input-bank-1\\\/\"},\"wordCount\":1113,\"commentCount\":0,\"publisher\":{\"@id\":\"https:\\\/\\\/www.fs1inc.com\\\/blog\\\/#organization\"},\"image\":{\"@id\":\"https:\\\/\\\/www.fs1inc.com\\\/blog\\\/dtc-p1391-glow-plug-circuit-low-input-bank-1\\\/#primaryimage\"},\"thumbnailUrl\":\"https:\\\/\\\/www.fs1inc.com\\\/blog\\\/wp-content\\\/uploads\\\/2025\\\/12\\\/fs1inc_logo2-scaled.jpg\",\"articleSection\":[\"Auto News\"],\"inLanguage\":\"en-US\",\"potentialAction\":[{\"@type\":\"CommentAction\",\"name\":\"Comment\",\"target\":[\"https:\\\/\\\/www.fs1inc.com\\\/blog\\\/dtc-p1391-glow-plug-circuit-low-input-bank-1\\\/#respond\"]}]},{\"@type\":\"WebPage\",\"@id\":\"https:\\\/\\\/www.fs1inc.com\\\/blog\\\/dtc-p1391-glow-plug-circuit-low-input-bank-1\\\/\",\"url\":\"https:\\\/\\\/www.fs1inc.com\\\/blog\\\/dtc-p1391-glow-plug-circuit-low-input-bank-1\\\/\",\"name\":\"P1391 Code Symptoms, Causes, Diagnosis & Repair Guide Step-by-Step - Flagship One Blog\",\"isPartOf\":{\"@id\":\"https:\\\/\\\/www.fs1inc.com\\\/blog\\\/#website\"},\"primaryImageOfPage\":{\"@id\":\"https:\\\/\\\/www.fs1inc.com\\\/blog\\\/dtc-p1391-glow-plug-circuit-low-input-bank-1\\\/#primaryimage\"},\"image\":{\"@id\":\"https:\\\/\\\/www.fs1inc.com\\\/blog\\\/dtc-p1391-glow-plug-circuit-low-input-bank-1\\\/#primaryimage\"},\"thumbnailUrl\":\"https:\\\/\\\/www.fs1inc.com\\\/blog\\\/wp-content\\\/uploads\\\/2025\\\/12\\\/fs1inc_logo2-scaled.jpg\",\"datePublished\":\"2025-12-10T16:58:06+00:00\",\"breadcrumb\":{\"@id\":\"https:\\\/\\\/www.fs1inc.com\\\/blog\\\/dtc-p1391-glow-plug-circuit-low-input-bank-1\\\/#breadcrumb\"},\"inLanguage\":\"en-US\",\"potentialAction\":[{\"@type\":\"ReadAction\",\"target\":[\"https:\\\/\\\/www.fs1inc.com\\\/blog\\\/dtc-p1391-glow-plug-circuit-low-input-bank-1\\\/\"]}]},{\"@type\":\"ImageObject\",\"inLanguage\":\"en-US\",\"@id\":\"https:\\\/\\\/www.fs1inc.com\\\/blog\\\/dtc-p1391-glow-plug-circuit-low-input-bank-1\\\/#primaryimage\",\"url\":\"https:\\\/\\\/www.fs1inc.com\\\/blog\\\/wp-content\\\/uploads\\\/2025\\\/12\\\/fs1inc_logo2-scaled.jpg\",\"contentUrl\":\"https:\\\/\\\/www.fs1inc.com\\\/blog\\\/wp-content\\\/uploads\\\/2025\\\/12\\\/fs1inc_logo2-scaled.jpg\",\"width\":2560,\"height\":617},{\"@type\":\"BreadcrumbList\",\"@id\":\"https:\\\/\\\/www.fs1inc.com\\\/blog\\\/dtc-p1391-glow-plug-circuit-low-input-bank-1\\\/#breadcrumb\",\"itemListElement\":[{\"@type\":\"ListItem\",\"position\":1,\"name\":\"Home\",\"item\":\"https:\\\/\\\/www.fs1inc.com\\\/blog\\\/\"},{\"@type\":\"ListItem\",\"position\":2,\"name\":\"P1391 Code Symptoms, Causes, Diagnosis &#038; Repair Guide Step-by-Step\"}]},{\"@type\":\"WebSite\",\"@id\":\"https:\\\/\\\/www.fs1inc.com\\\/blog\\\/#website\",\"url\":\"https:\\\/\\\/www.fs1inc.com\\\/blog\\\/\",\"name\":\"Flagship One Blog\",\"description\":\"Flagship One Inc. OEM Engine Computers  Control Modules\",\"publisher\":{\"@id\":\"https:\\\/\\\/www.fs1inc.com\\\/blog\\\/#organization\"},\"potentialAction\":[{\"@type\":\"SearchAction\",\"target\":{\"@type\":\"EntryPoint\",\"urlTemplate\":\"https:\\\/\\\/www.fs1inc.com\\\/blog\\\/?s={search_term_string}\"},\"query-input\":{\"@type\":\"PropertyValueSpecification\",\"valueRequired\":true,\"valueName\":\"search_term_string\"}}],\"inLanguage\":\"en-US\"},{\"@type\":\"Organization\",\"@id\":\"https:\\\/\\\/www.fs1inc.com\\\/blog\\\/#organization\",\"name\":\"Flagship One, Inc.\",\"url\":\"https:\\\/\\\/www.fs1inc.com\\\/blog\\\/\",\"logo\":{\"@type\":\"ImageObject\",\"inLanguage\":\"en-US\",\"@id\":\"https:\\\/\\\/www.fs1inc.com\\\/blog\\\/#\\\/schema\\\/logo\\\/image\\\/\",\"url\":\"https:\\\/\\\/www.fs1inc.com\\\/blog\\\/wp-content\\\/uploads\\\/2019\\\/06\\\/web-lg-fs1-logo.png\",\"contentUrl\":\"https:\\\/\\\/www.fs1inc.com\\\/blog\\\/wp-content\\\/uploads\\\/2019\\\/06\\\/web-lg-fs1-logo.png\",\"width\":1341,\"height\":1098,\"caption\":\"Flagship One, Inc.\"},\"image\":{\"@id\":\"https:\\\/\\\/www.fs1inc.com\\\/blog\\\/#\\\/schema\\\/logo\\\/image\\\/\"},\"sameAs\":[\"https:\\\/\\\/www.facebook.com\\\/flagshipone\",\"https:\\\/\\\/x.com\\\/theflagshipone\",\"https:\\\/\\\/www.instagram.com\\\/flagship_one\",\"https:\\\/\\\/www.youtube.com\\\/channel\\\/UC0oyKphffBM2qkJ-gKPmMXw\"]},{\"@type\":\"Person\",\"@id\":\"https:\\\/\\\/www.fs1inc.com\\\/blog\\\/#\\\/schema\\\/person\\\/a3cf463514bd03eb7656953ef8f75700\",\"name\":\"FlagshipOne\",\"image\":{\"@type\":\"ImageObject\",\"inLanguage\":\"en-US\",\"@id\":\"https:\\\/\\\/secure.gravatar.com\\\/avatar\\\/351b81e51993825aea73280c48061a7205fdd2189730ebbdee5d63894c5cebb4?s=96&d=mm&r=g\",\"url\":\"https:\\\/\\\/secure.gravatar.com\\\/avatar\\\/351b81e51993825aea73280c48061a7205fdd2189730ebbdee5d63894c5cebb4?s=96&d=mm&r=g\",\"contentUrl\":\"https:\\\/\\\/secure.gravatar.com\\\/avatar\\\/351b81e51993825aea73280c48061a7205fdd2189730ebbdee5d63894c5cebb4?s=96&d=mm&r=g\",\"caption\":\"FlagshipOne\"},\"description\":\"The world's top supplier of programmed OEM (Original Equipment Manufacturer) Powertrain Control Modules (PCM), Engine Control Modules (ECM), Injection Control Modules (IDM), Body Control Modules (BCM), Transmission Control Modules (TCM), Engine Control Units and all other car control units. With over a decade in the business, we are the most reliable source when it comes to programming services for replacement engine control modules.\",\"sameAs\":[\"https:\\\/\\\/www.fs1inc.com\\\/\",\"https:\\\/\\\/www.facebook.com\\\/flagshipone\\\/\",\"https:\\\/\\\/www.instagram.com\\\/flagship_one\\\/\",\"https:\\\/\\\/www.linkedin.com\\\/company\\\/fs1inc\"],\"url\":\"https:\\\/\\\/www.fs1inc.com\\\/blog\\\/author\\\/flagship1inc\\\/\"}]}<\/script>\n<!-- \/ Yoast SEO plugin. -->","yoast_head_json":{"title":"P1391 Code Symptoms, Causes, Diagnosis & Repair Guide Step-by-Step - Flagship One Blog","robots":{"index":"index","follow":"follow","max-snippet":"max-snippet:-1","max-image-preview":"max-image-preview:large","max-video-preview":"max-video-preview:-1"},"canonical":"https:\/\/www.fs1inc.com\/blog\/dtc-p1391-glow-plug-circuit-low-input-bank-1\/","og_locale":"en_US","og_type":"article","og_title":"P1391 Code Symptoms, Causes, Diagnosis & Repair Guide Step-by-Step - Flagship One Blog","og_description":"Your diesel won\u2019t start or cranks weak \u2013 P1391 signals low\u2011input glow plug circuit Bank 1. Diagnose wiring or module fault to prevent engine damage.","og_url":"https:\/\/www.fs1inc.com\/blog\/dtc-p1391-glow-plug-circuit-low-input-bank-1\/","og_site_name":"Flagship One Blog","article_publisher":"https:\/\/www.facebook.com\/flagshipone","article_author":"https:\/\/www.facebook.com\/flagshipone\/","article_published_time":"2025-12-10T16:58:06+00:00","og_image":[{"url":"https:\/\/www.fs1inc.com\/blog\/wp-content\/uploads\/2025\/12\/fs1inc_logo2-scaled.jpg","type":"","width":"","height":""}],"author":"FlagshipOne","twitter_card":"summary_large_image","twitter_creator":"@theflagshipone","twitter_site":"@theflagshipone","twitter_misc":{"Written by":"FlagshipOne","Est. reading time":"6 minutes"},"schema":{"@context":"https:\/\/schema.org","@graph":[{"@type":"Article","@id":"https:\/\/www.fs1inc.com\/blog\/dtc-p1391-glow-plug-circuit-low-input-bank-1\/#article","isPartOf":{"@id":"https:\/\/www.fs1inc.com\/blog\/dtc-p1391-glow-plug-circuit-low-input-bank-1\/"},"author":{"name":"FlagshipOne","@id":"https:\/\/www.fs1inc.com\/blog\/#\/schema\/person\/a3cf463514bd03eb7656953ef8f75700"},"headline":"P1391 Code Symptoms, Causes, Diagnosis &#038; Repair Guide Step-by-Step","datePublished":"2025-12-10T16:58:06+00:00","mainEntityOfPage":{"@id":"https:\/\/www.fs1inc.com\/blog\/dtc-p1391-glow-plug-circuit-low-input-bank-1\/"},"wordCount":1113,"commentCount":0,"publisher":{"@id":"https:\/\/www.fs1inc.com\/blog\/#organization"},"image":{"@id":"https:\/\/www.fs1inc.com\/blog\/dtc-p1391-glow-plug-circuit-low-input-bank-1\/#primaryimage"},"thumbnailUrl":"https:\/\/www.fs1inc.com\/blog\/wp-content\/uploads\/2025\/12\/fs1inc_logo2-scaled.jpg","articleSection":["Auto News"],"inLanguage":"en-US","potentialAction":[{"@type":"CommentAction","name":"Comment","target":["https:\/\/www.fs1inc.com\/blog\/dtc-p1391-glow-plug-circuit-low-input-bank-1\/#respond"]}]},{"@type":"WebPage","@id":"https:\/\/www.fs1inc.com\/blog\/dtc-p1391-glow-plug-circuit-low-input-bank-1\/","url":"https:\/\/www.fs1inc.com\/blog\/dtc-p1391-glow-plug-circuit-low-input-bank-1\/","name":"P1391 Code Symptoms, Causes, Diagnosis & Repair Guide Step-by-Step - Flagship One Blog","isPartOf":{"@id":"https:\/\/www.fs1inc.com\/blog\/#website"},"primaryImageOfPage":{"@id":"https:\/\/www.fs1inc.com\/blog\/dtc-p1391-glow-plug-circuit-low-input-bank-1\/#primaryimage"},"image":{"@id":"https:\/\/www.fs1inc.com\/blog\/dtc-p1391-glow-plug-circuit-low-input-bank-1\/#primaryimage"},"thumbnailUrl":"https:\/\/www.fs1inc.com\/blog\/wp-content\/uploads\/2025\/12\/fs1inc_logo2-scaled.jpg","datePublished":"2025-12-10T16:58:06+00:00","breadcrumb":{"@id":"https:\/\/www.fs1inc.com\/blog\/dtc-p1391-glow-plug-circuit-low-input-bank-1\/#breadcrumb"},"inLanguage":"en-US","potentialAction":[{"@type":"ReadAction","target":["https:\/\/www.fs1inc.com\/blog\/dtc-p1391-glow-plug-circuit-low-input-bank-1\/"]}]},{"@type":"ImageObject","inLanguage":"en-US","@id":"https:\/\/www.fs1inc.com\/blog\/dtc-p1391-glow-plug-circuit-low-input-bank-1\/#primaryimage","url":"https:\/\/www.fs1inc.com\/blog\/wp-content\/uploads\/2025\/12\/fs1inc_logo2-scaled.jpg","contentUrl":"https:\/\/www.fs1inc.com\/blog\/wp-content\/uploads\/2025\/12\/fs1inc_logo2-scaled.jpg","width":2560,"height":617},{"@type":"BreadcrumbList","@id":"https:\/\/www.fs1inc.com\/blog\/dtc-p1391-glow-plug-circuit-low-input-bank-1\/#breadcrumb","itemListElement":[{"@type":"ListItem","position":1,"name":"Home","item":"https:\/\/www.fs1inc.com\/blog\/"},{"@type":"ListItem","position":2,"name":"P1391 Code Symptoms, Causes, Diagnosis &#038; Repair Guide Step-by-Step"}]},{"@type":"WebSite","@id":"https:\/\/www.fs1inc.com\/blog\/#website","url":"https:\/\/www.fs1inc.com\/blog\/","name":"Flagship One Blog","description":"Flagship One Inc. OEM Engine Computers  Control Modules","publisher":{"@id":"https:\/\/www.fs1inc.com\/blog\/#organization"},"potentialAction":[{"@type":"SearchAction","target":{"@type":"EntryPoint","urlTemplate":"https:\/\/www.fs1inc.com\/blog\/?s={search_term_string}"},"query-input":{"@type":"PropertyValueSpecification","valueRequired":true,"valueName":"search_term_string"}}],"inLanguage":"en-US"},{"@type":"Organization","@id":"https:\/\/www.fs1inc.com\/blog\/#organization","name":"Flagship One, Inc.","url":"https:\/\/www.fs1inc.com\/blog\/","logo":{"@type":"ImageObject","inLanguage":"en-US","@id":"https:\/\/www.fs1inc.com\/blog\/#\/schema\/logo\/image\/","url":"https:\/\/www.fs1inc.com\/blog\/wp-content\/uploads\/2019\/06\/web-lg-fs1-logo.png","contentUrl":"https:\/\/www.fs1inc.com\/blog\/wp-content\/uploads\/2019\/06\/web-lg-fs1-logo.png","width":1341,"height":1098,"caption":"Flagship One, Inc."},"image":{"@id":"https:\/\/www.fs1inc.com\/blog\/#\/schema\/logo\/image\/"},"sameAs":["https:\/\/www.facebook.com\/flagshipone","https:\/\/x.com\/theflagshipone","https:\/\/www.instagram.com\/flagship_one","https:\/\/www.youtube.com\/channel\/UC0oyKphffBM2qkJ-gKPmMXw"]},{"@type":"Person","@id":"https:\/\/www.fs1inc.com\/blog\/#\/schema\/person\/a3cf463514bd03eb7656953ef8f75700","name":"FlagshipOne","image":{"@type":"ImageObject","inLanguage":"en-US","@id":"https:\/\/secure.gravatar.com\/avatar\/351b81e51993825aea73280c48061a7205fdd2189730ebbdee5d63894c5cebb4?s=96&d=mm&r=g","url":"https:\/\/secure.gravatar.com\/avatar\/351b81e51993825aea73280c48061a7205fdd2189730ebbdee5d63894c5cebb4?s=96&d=mm&r=g","contentUrl":"https:\/\/secure.gravatar.com\/avatar\/351b81e51993825aea73280c48061a7205fdd2189730ebbdee5d63894c5cebb4?s=96&d=mm&r=g","caption":"FlagshipOne"},"description":"The world's top supplier of programmed OEM (Original Equipment Manufacturer) Powertrain Control Modules (PCM), Engine Control Modules (ECM), Injection Control Modules (IDM), Body Control Modules (BCM), Transmission Control Modules (TCM), Engine Control Units and all other car control units. With over a decade in the business, we are the most reliable source when it comes to programming services for replacement engine control modules.","sameAs":["https:\/\/www.fs1inc.com\/","https:\/\/www.facebook.com\/flagshipone\/","https:\/\/www.instagram.com\/flagship_one\/","https:\/\/www.linkedin.com\/company\/fs1inc"],"url":"https:\/\/www.fs1inc.com\/blog\/author\/flagship1inc\/"}]}},"_links":{"self":[{"href":"https:\/\/www.fs1inc.com\/blog\/wp-json\/wp\/v2\/posts\/517966","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.fs1inc.com\/blog\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.fs1inc.com\/blog\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.fs1inc.com\/blog\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/www.fs1inc.com\/blog\/wp-json\/wp\/v2\/comments?post=517966"}],"version-history":[{"count":0,"href":"https:\/\/www.fs1inc.com\/blog\/wp-json\/wp\/v2\/posts\/517966\/revisions"}],"wp:attachment":[{"href":"https:\/\/www.fs1inc.com\/blog\/wp-json\/wp\/v2\/media?parent=517966"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.fs1inc.com\/blog\/wp-json\/wp\/v2\/categories?post=517966"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.fs1inc.com\/blog\/wp-json\/wp\/v2\/tags?post=517966"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}