John Deere 5018.15 – Engine Control Unit (ECU): The ECU Has Noted Possible Contamination In The DOC (ECU)

The engine control system has detected that the calculated amount of unintended combustible materials (such as unburned fuel, engine oil, or coolant) entering the Diesel Oxidation Catalyst (DOC) is slightly higher than expected. This causes an unexpected temperature spike in the exhaust filter during operation or regeneration, resulting in active exhaust filter cleaning becoming unavailable and engine power being limited.

• 5085E
• 5090E
• 5090EL
• 5100E
• 5085M
• 5100M
• 5100MH
• 5100ML
• 5115ML
• 5090M
• 5115M
• 6110M
• 6120M
• 6130M
• 6145M
• 6155M
• 6175M
• 6195M
• 6110R
• 6120R
• 6130R
• 6145R
• 6155R
• 6175R
• 6195R
• 6215R
• 5095M
• 5105M
• 6090MC
• 6100MC
• 6110MC
• 6090RC
• 6100RC
• 6110RC
• 8235R
• 8260R
• 8285R
• 8310R
• 8335R
• 8360R
• 8310RT
• 8335RT
• 8360RT
• 9470RT
• 9520RT
• 9570RT
• 7760
• 7180
• 7280
• 7380
• 7480
• S680
• S690
• D24x40 S3

1. 1

   Check the Fuel Dosing System (hydrocarbon doser/7th injector) for leaks, improper atomization, or a stuck-open condition dumping raw fuel into the exhaust

2. 2

   Inspect turbocharger oil seals for leaks that could be passing oil directly into the exhaust stream

3. 3

   Diagnose the main engine fuel injectors for leaks or poor atomization causing unburned fuel

4. 4

   Inspect the EGR cooler and head gasket for internal leaks passing coolant into the exhaust

5. 5

   Verify the DOC inlet and outlet temperature sensors are reading accurately and not falsely reporting high temperatures

1. 1

   Resolve the Upstream Leak

   Repair the root cause of the contamination first (e.g., replace the leaking fuel doser, rebuild the turbocharger, or replace faulty engine fuel injectors).

2. 2

   Inspect the DOC/DPF

   Remove the Diesel Oxidation Catalyst (DOC) and Diesel Particulate Filter (DPF). Inspect the face of the catalyst for face-plugging, oil/coolant soaking, or thermal damage (melting/cracking) caused by the unexpected temperature spikes.

3. 3

   Clean or Replace the Catalyst

   If the DOC/DPF is heavily contaminated but structurally intact, send it to a professional facility to be baked and pneumatically cleaned. If the DOC is melted, thermally degraded, or irreversibly plugged, it must be replaced.

4. 4

   Reassemble and Reset

   Reinstall the aftertreatment components with new gaskets.

5. 5

   Perform a Service Regeneration

   Connect John Deere Service ADVISOR (or an equivalent diagnostic tool) and command a stationary Service Regeneration. Monitor the DOC inlet/outlet temperatures to verify the repair is successful and to clear the active 005018.15 code.