01 What Happens If You Shift to First Gear at High Speed? • 02 The Motorist’s Manual: Adding Oil to Your Warm Engine • 03 The Complete Guide to the Major Parts of an Excavator • 04 P0045, P0046, P0047, and P0048: Turbo or Supercharger Boost… • 05 Can a Fuel Injector Cleaner Damage Your Engine? Here’s What… • 06 Check Engine Light: A Comprehensive Guide to Resetting and … • 07 How to Calculate Height Using Angle and Distance • 08 The Hidden Tech Inside Modern Cars Most Drivers Don’t Under… • 09 This Is Why Car Thieves Check Your Mirrors For Valuables • 10 Unlocking the Power of Differential Lock: Traction, Problem… •

DTC codes / BMW codes / P1401

P1401 · BMWHeated Catalyst Current Too High During Heating Bank 1

P1401 on BMW vehicles means the engine control module (DME) has detected that the electrical current drawn by the heated catalyst on bank 1 is higher than expected during the heating phase. The DME monitors this current to ensure the catalyst reaches operating temperature quickly after a cold start, and an excessively high reading indicates a short circuit or excessive load in the heater circuit.

SystemPowertrain
Code typeBMW specific
SeverityMedium
Fix difficultyIntermediate
AreaAuxiliary emission controls

Symptoms you may notice

  • Illumination of the check engine light (malfunction indicator lamp) on the dashboard.
  • Often no other symptoms besides the warning light, especially if the catalyst still reaches temperature passively.
  • Possible slight delay in cold-start emissions reduction, which may not be noticeable to the driver.
  • In rare cases, a blown fuse for the secondary air or catalyst heater circuit, leading to additional codes.
  • No noticeable performance or drivability issues in most cases because the fault affects emissions control, not engine operation.

Common causes, most likely first

  1. Short circuit to ground in the heated catalyst wiring harness, often due to chafing or insulation damage.
  2. Faulty heated catalyst element (internal short) inside the catalytic converter assembly.
  3. Corroded or damaged electrical connector at the heated catalyst or DME, causing excessive current draw.
  4. Failed catalyst heater relay or control module (if equipped) that stays closed and applies continuous power.
  5. Water intrusion into the heater circuit connector or wiring, leading to a partial short.
  6. DME internal fault incorrectly interpreting current feedback (less common).

How to diagnose and fix it

  1. Check for any related fault codes (e.g., P1400, P1402) and freeze-frame data to confirm the fault is current and not historical.
  2. Inspect the heated catalyst wiring harness and connector for visible damage, corrosion, or signs of overheating; repair or replace as needed.
  3. Measure resistance of the heated catalyst element with a multimeter and compare to BMW specifications; replace the catalyst if out of range.
  4. Test the catalyst heater relay (if applicable) for proper operation and replace if stuck closed.
  5. Check for short to ground in the wiring between the DME and the heated catalyst using a multimeter and wiring diagram.
  6. If all external components test good, suspect the DME and perform further diagnostics or replacement as per BMW service procedures.

Before replacing the catalytic converter

  • A common misdiagnosis is replacing the catalytic converter when the real problem is a chafed wiring harness shorting to ground, which is far cheaper to fix.
  • The heated catalyst is only active during cold starts, so the fault may not appear during a warm engine diagnostic; always perform tests with a cold engine.
  • On some BMW models, the heated catalyst is controlled by the DME via a relay, and a stuck relay can cause excessive current draw even with a good catalyst.
  • Water ingress into the connector at the catalyst can cause intermittent high current readings that may not set a code every drive cycle.
  • P1401 can be set by a low battery or charging system issue that causes voltage spikes, so always check battery health and charging voltage first.

Can I keep driving with P1401?

You can generally continue driving with P1401 because the engine management system will default to a safe mode and the catalyst will still function once warmed up, but avoid prolonged idling and schedule diagnosis soon to prevent potential wiring damage or emissions test failure.

Tools that help

Tools we recommend are in the Auto Veteran shop on Amazon. As an Amazon Associate we earn from qualifying purchases.

Guidance is general and written for BMW vehicles. Exact tests and values vary by model, so confirm the fault before replacing parts.

Running on fumes Free guides aren't free to make. Top up the tank. Any amount, one time. Fuel the Garage