80518A

What the Code Means

Code 80518A points to a short to ground in the AdBlue supply line heater. The heater keeps AdBlue from freezing at low temperatures. A short circuit disables the heater, which can let the fluid freeze and disrupt dosing.

How the System Works

The AdBlue supply line has an electric heater that kicks in at low temperatures to keep the solution flowing. The heater is controlled by the SCR (Selective Catalytic Reduction) control module and has a set resistance, usually 2–5 ohms. With a short to ground, resistance drops, current spikes, and the circuit shuts off or the fuse blows.

Components Involved

• AdBlue supply line (BMW OEM part number 16117212539)
• SCR control module
• Heater circuit fuse

Symptoms

Indicators

• Check Engine Light comes on

Behavior

• In cold weather, a No Start countdown may begin
• Reduced AdBlue dosing

Conditions

• Symptoms are most noticeable in sub-freezing weather, when AdBlue can freeze

Diagnosis and Repair

Step 1: Visual Inspection

• Check the AdBlue supply line wiring for damage, corrosion, or chafing
• Inspect the connectors for oxidation or contamination

Step 2: Measure Heater Resistance

• Disconnect the supply line connector
• Use a multimeter to measure resistance across the heater terminals
• Normal value: 2–5 ohms
• If resistance is near 0 ohms or reads open, the heater is faulty

Step 3: Check the Power Circuit

• With the ignition on, check for power at the connector (per the wiring diagram)
• Check the heater circuit fuse

Step 4: Replace the Supply Line

• If the heater is faulty, replace the AdBlue supply line as a complete assembly
• Recommended BMW OEM part number: 16117212539

Step 5: Clear Codes and Verify

• After the repair, clear the fault codes
• Take a test drive in cold conditions to confirm the heater works

Secondary Problems

Ignoring the fault can lead to the following:

1. AdBlue freezing — below freezing, without the heater the fluid freezes and blocks the supply line
2. Dosing failure — frozen AdBlue won't be injected into the SCR catalytic converter
3. Reduced SCR efficiency — without AdBlue, the nitrogen oxide (NOx) reduction system stops working, which can push emissions over the limit
4. Catalytic converter damage — running without AdBlue dosing for a long time can damage the SCR catalytic converter through overheating or clogging

Severity

• In cold-climate regions, fix the problem right away
• Replacing the AdBlue supply line costs far less than repairing the SCR catalytic converter