{"id":40127,"date":"2026-03-28T00:58:14","date_gmt":"2026-03-27T22:58:14","guid":{"rendered":"https:\/\/diagnozabam.ro\/sfaturi\/?p=40127"},"modified":"2026-03-28T00:58:14","modified_gmt":"2026-03-27T22:58:14","slug":"p0155-code-o2-sensor-heater-circuit-malfunction","status":"publish","type":"post","link":"https:\/\/diagnozabam.ro\/sfaturi\/blog\/p0155-code-o2-sensor-heater-circuit-malfunction\/","title":{"rendered":"P0155 Code \u2013 O2 Sensor Heater Circuit Malfunction"},"content":{"rendered":"<p data-start=\"145\" data-end=\"322\">The P0155 diagnostic trouble code indicates that the Engine Control Unit (ECU) has detected a malfunction in the <strong data-start=\"258\" data-end=\"276\">heater circuit<\/strong> of the oxygen (O2) sensor on Bank 2 Sensor 1.<\/p>\n<p data-start=\"324\" data-end=\"518\">The heater element inside the O2 sensor helps it reach optimal operating temperature quickly after engine start. Without proper heating, the sensor responds slowly or may not function correctly.<\/p>\n<p data-start=\"520\" data-end=\"635\">When the ECU detects that the heater circuit is not operating within expected parameters, it stores the P0155 code.<\/p>\n<hr data-start=\"637\" data-end=\"640\" \/>\n<h2 data-section-id=\"1e1vpr6\" data-start=\"642\" data-end=\"667\">Symptoms of Code P0155<\/h2>\n<p data-start=\"669\" data-end=\"693\">Common symptoms include:<\/p>\n<ul data-start=\"695\" data-end=\"899\">\n<li data-section-id=\"v00yak\" data-start=\"695\" data-end=\"729\">\n<p data-start=\"697\" data-end=\"729\"><a href=\"https:\/\/diagnozabam.ro\/sfaturi\/blog\/%e2%9a%99%ef%b8%8f-faulty-maf-sensor-symptoms-causes-fixes\/\">Check Engine<\/a> Light illuminated<\/p>\n<\/li>\n<li data-section-id=\"1ymj31f\" data-start=\"730\" data-end=\"784\">\n<p data-start=\"732\" data-end=\"784\">Increased fuel consumption (especially <a href=\"https:\/\/diagnozabam.ro\/sfaturi\/blog\/common-winter-car-starting-mistakes\/\">cold start<\/a>)<\/p>\n<\/li>\n<li data-section-id=\"10619uy\" data-start=\"785\" data-end=\"818\">\n<p data-start=\"787\" data-end=\"818\">Delayed closed-loop operation<\/p>\n<\/li>\n<li data-section-id=\"1tmtup\" data-start=\"819\" data-end=\"863\">\n<p data-start=\"821\" data-end=\"863\">Slight rough running when engine is <a href=\"https:\/\/diagnozabam.ro\/sfaturi\/blog\/common-winter-car-starting-mistakes\/\">cold<\/a><\/p>\n<\/li>\n<li data-section-id=\"1oq07pl\" data-start=\"864\" data-end=\"899\">\n<p data-start=\"866\" data-end=\"899\">Higher <a href=\"https:\/\/diagnozabam.ro\/sfaturi\/blog\/wet-vs-dry-timing-belt-what-drivers-must-know\/\">emissions<\/a> during warm-up<\/p>\n<\/li>\n<\/ul>\n<hr data-start=\"901\" data-end=\"904\" \/>\n<h2 data-section-id=\"1qen03m\" data-start=\"906\" data-end=\"931\">Common Causes of P0155<\/h2>\n<p data-start=\"933\" data-end=\"956\">Typical causes include:<\/p>\n<ul data-start=\"958\" data-end=\"1156\">\n<li data-section-id=\"13ej91p\" data-start=\"958\" data-end=\"1003\">\n<p data-start=\"960\" data-end=\"1003\">Faulty O2 sensor heater (Bank 2 Sensor 1)<\/p>\n<\/li>\n<li data-section-id=\"15tinwd\" data-start=\"1004\" data-end=\"1044\">\n<p data-start=\"1006\" data-end=\"1044\">Blown fuse related to heater circuit<\/p>\n<\/li>\n<li data-section-id=\"15448se\" data-start=\"1045\" data-end=\"1071\">\n<p data-start=\"1047\" data-end=\"1071\">Open or shorted wiring<\/p>\n<\/li>\n<li data-section-id=\"1e87jy1\" data-start=\"1072\" data-end=\"1104\">\n<p data-start=\"1074\" data-end=\"1104\">Corroded or loose connectors<\/p>\n<\/li>\n<li data-section-id=\"eyt49r\" data-start=\"1105\" data-end=\"1135\">\n<p data-start=\"1107\" data-end=\"1135\">Faulty relay (if equipped)<\/p>\n<\/li>\n<li data-section-id=\"1s60s8k\" data-start=\"1136\" data-end=\"1156\">\n<p data-start=\"1138\" data-end=\"1156\">ECU fault (rare)<\/p>\n<\/li>\n<\/ul>\n<hr data-start=\"1158\" data-end=\"1161\" \/>\n<h2 data-section-id=\"1a4mwdz\" data-start=\"1163\" data-end=\"1191\">How Serious Is Code P0155<\/h2>\n<p data-start=\"1193\" data-end=\"1259\">The P0155 code is considered a <strong data-start=\"1224\" data-end=\"1258\">low to moderate severity issue<\/strong>.<\/p>\n<p data-start=\"1261\" data-end=\"1295\">The vehicle remains drivable, but:<\/p>\n<ul data-start=\"1297\" data-end=\"1400\">\n<li data-section-id=\"1p9t17s\" data-start=\"1297\" data-end=\"1347\">\n<p data-start=\"1299\" data-end=\"1347\">engine efficiency during <a href=\"https:\/\/diagnozabam.ro\/sfaturi\/blog\/common-winter-car-starting-mistakes\/\">cold start<\/a> is reduced<\/p>\n<\/li>\n<li data-section-id=\"89fvkm\" data-start=\"1348\" data-end=\"1370\">\n<p data-start=\"1350\" data-end=\"1370\"><a href=\"https:\/\/diagnozabam.ro\/sfaturi\/blog\/wet-vs-dry-timing-belt-what-drivers-must-know\/\">emissions<\/a> increase<\/p>\n<\/li>\n<li data-section-id=\"1qujb5b\" data-start=\"1371\" data-end=\"1400\">\n<p data-start=\"1373\" data-end=\"1400\">fuel consumption may rise<\/p>\n<\/li>\n<\/ul>\n<p data-start=\"1402\" data-end=\"1439\">Repair is recommended but not urgent.<\/p>\n<hr data-start=\"1441\" data-end=\"1444\" \/>\n<h2 data-section-id=\"16vv9u6\" data-start=\"1446\" data-end=\"1475\">How to Diagnose Code P0155<\/h2>\n<p data-start=\"1477\" data-end=\"1506\">Diagnosis typically involves:<\/p>\n<ol data-start=\"1508\" data-end=\"1747\">\n<li data-section-id=\"1sps9us\" data-start=\"1508\" data-end=\"1551\">\n<p data-start=\"1511\" data-end=\"1551\">Scanning the vehicle with an <a href=\"https:\/\/diagnozabam.ro\/sfaturi\/blog\/p0229-code-throttle-pedal-position-sensor-c-intermittent\/\">OBD2<\/a> tool<\/p>\n<\/li>\n<li data-section-id=\"1p2bicg\" data-start=\"1552\" data-end=\"1591\">\n<p data-start=\"1555\" data-end=\"1591\">Checking heater circuit resistance<\/p>\n<\/li>\n<li data-section-id=\"aovsvh\" data-start=\"1592\" data-end=\"1630\">\n<p data-start=\"1595\" data-end=\"1630\">Verifying power and ground supply<\/p>\n<\/li>\n<li data-section-id=\"1wdq2qm\" data-start=\"1631\" data-end=\"1668\">\n<p data-start=\"1634\" data-end=\"1668\">Inspecting wiring and connectors<\/p>\n<\/li>\n<li data-section-id=\"fn23p6\" data-start=\"1669\" data-end=\"1707\">\n<p data-start=\"1672\" data-end=\"1707\">Checking related fuses and relays<\/p>\n<\/li>\n<li data-section-id=\"1sywoh6\" data-start=\"1708\" data-end=\"1747\">\n<p data-start=\"1711\" data-end=\"1747\">Monitoring sensor warm-up behavior<\/p>\n<\/li>\n<\/ol>\n<p data-start=\"1749\" data-end=\"1792\">A faulty heater circuit confirms the issue.<\/p>\n<hr data-start=\"1794\" data-end=\"1797\" \/>\n<h2 data-section-id=\"fx0lgl\" data-start=\"1799\" data-end=\"1823\">How to Fix Code P0155<\/h2>\n<p data-start=\"1825\" data-end=\"1857\">Common repair solutions include:<\/p>\n<ul data-start=\"1859\" data-end=\"2033\">\n<li data-section-id=\"416ig1\" data-start=\"1859\" data-end=\"1904\">\n<p data-start=\"1861\" data-end=\"1904\">Replacing the O2 sensor (Bank 2 Sensor 1)<\/p>\n<\/li>\n<li data-section-id=\"1doi7pr\" data-start=\"1905\" data-end=\"1930\">\n<p data-start=\"1907\" data-end=\"1930\">Replacing blown fuses<\/p>\n<\/li>\n<li data-section-id=\"ezgzpw\" data-start=\"1931\" data-end=\"1965\">\n<p data-start=\"1933\" data-end=\"1965\">Repairing wiring or connectors<\/p>\n<\/li>\n<li data-section-id=\"1c0uq4x\" data-start=\"1966\" data-end=\"1992\">\n<p data-start=\"1968\" data-end=\"1992\">Replacing faulty relay<\/p>\n<\/li>\n<li data-section-id=\"5eglti\" data-start=\"1993\" data-end=\"2033\">\n<p data-start=\"1995\" data-end=\"2033\">Clearing the fault code after repair<\/p>\n<\/li>\n<\/ul>\n<p data-start=\"2035\" data-end=\"2090\">In most cases, replacing the sensor resolves the issue.<\/p>\n<hr data-start=\"2092\" data-end=\"2095\" \/>\n<h2 data-section-id=\"1dcwvgk\" data-start=\"2097\" data-end=\"2126\">Vehicles Commonly Affected<\/h2>\n<p data-start=\"2128\" data-end=\"2206\">The P0155 code may appear on vehicles with multiple cylinder banks, including:<\/p>\n<ul data-start=\"2208\" data-end=\"2273\">\n<li data-section-id=\"16yn0uo\" data-start=\"2208\" data-end=\"2215\">\n<p data-start=\"2210\" data-end=\"2215\"><a href=\"https:\/\/diagnozabam.ro\/sfaturi\/blog\/bmw-art-car-world-tour-expands-to-romania\/\">BMW<\/a><\/p>\n<\/li>\n<li data-section-id=\"1xesam0\" data-start=\"2216\" data-end=\"2233\">\n<p data-start=\"2218\" data-end=\"2233\">Mercedes-Benz<\/p>\n<\/li>\n<li data-section-id=\"1wjv8mp\" data-start=\"2234\" data-end=\"2242\">\n<p data-start=\"2236\" data-end=\"2242\"><a href=\"https:\/\/diagnozabam.ro\/sfaturi\/engines\/audi\/\">Audi<\/a><\/p>\n<\/li>\n<li data-section-id=\"1xwxs7r\" data-start=\"2243\" data-end=\"2251\">\n<p data-start=\"2245\" data-end=\"2251\">Ford<\/p>\n<\/li>\n<li data-section-id=\"kxa3e8\" data-start=\"2252\" data-end=\"2262\">\n<p data-start=\"2254\" data-end=\"2262\">Toyota<\/p>\n<\/li>\n<li data-section-id=\"ibrl1c\" data-start=\"2263\" data-end=\"2273\">\n<p data-start=\"2265\" data-end=\"2273\">Nissan<\/p>\n<\/li>\n<\/ul>\n<hr data-start=\"2275\" data-end=\"2278\" \/>\n<h2 data-section-id=\"edutp8\" data-start=\"2280\" data-end=\"2299\">FAQ \u2013 P0155 Code<\/h2>\n<h3 data-section-id=\"1kzdevi\" data-start=\"2301\" data-end=\"2333\">Can I drive with code P0155?<\/h3>\n<p data-start=\"2335\" data-end=\"2394\">Yes, but fuel efficiency during <a href=\"https:\/\/diagnozabam.ro\/sfaturi\/blog\/common-winter-car-starting-mistakes\/\">cold<\/a> starts may be reduced.<\/p>\n<h3 data-section-id=\"11rf7nk\" data-start=\"2396\" data-end=\"2432\">What does the heater circuit do?<\/h3>\n<p data-start=\"2434\" data-end=\"2493\">It helps the O2 sensor reach operating temperature quickly.<\/p>\n<h3 data-section-id=\"5lp0c0\" data-start=\"2495\" data-end=\"2522\">Is this a common issue?<\/h3>\n<p data-start=\"2524\" data-end=\"2567\">Yes, especially on higher mileage vehicles.<\/p>\n","protected":false},"excerpt":{"rendered":"<p>The P0155 diagnostic trouble code indicates that the Engine Control Unit (ECU) has detected a malfunction in the heater circuit of the oxygen (O2) sensor on Bank 2 Sensor 1. The heater element inside the O2 sensor helps it reach optimal operating temperature quickly after engine start. Without proper heating, the sensor responds slowly or [&hellip;]<\/p>\n","protected":false},"author":1,"featured_media":10039,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_sitemap_exclude":false,"_sitemap_priority":"","_sitemap_frequency":"","footnotes":"","jetpack_publicize_message":"","jetpack_publicize_feature_enabled":true,"jetpack_social_post_already_shared":true,"jetpack_social_options":{"image_generator_settings":{"template":"highway","default_image_id":0,"font":"","enabled":false},"version":2}},"categories":[45415],"tags":[36299,36841,41073,36339,45999,46039,46001,45463,46211,46005,42874],"class_list":["post-40127","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-obd2-en","tag-bam","tag-car-diagnostics","tag-check-engine","tag-diagnoza","tag-engine-codes","tag-engine-fault-code","tag-obd2","tag-obd2-code","tag-p0155","tag-powertrain","tag-vehicle-diagnostics"],"yoast_head":"<!-- This site is optimized with the Yoast SEO Premium plugin v26.2 (Yoast SEO v27.6) - https:\/\/yoast.com\/product\/yoast-seo-premium-wordpress\/ -->\n<title>P0155 Code \u2013 O2 Sensor Heater Circuit Malfunction - Diagnoza BAM<\/title>\n<meta name=\"description\" content=\"P0155 code indicates a fault in the monitored system. 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