Code Definition

P16A4 — Selective Catalytic Reduction (SCR) – Fault During First Fill Test

System: Powertrain  |  Type: Manufacturer-Specific  |  Make: Land Rover

About P16A4

P16A4 is a manufacturer-specific powertrain diagnostic trouble code recorded for Land Rover vehicles. It belongs to the P-prefix family of codes, which covers engine, transmission, emissions, or fuel-system faults.

Scanning & clearing: A generic OBD-II scan tool will usually read and clear powertrain (P) codes. For live data, freeze-frame capture, and bi-directional tests you may need a more capable scan tool that supports the vehicle's ECM protocol.

P16A4 is a manufacturer-specific code. The same code string on a different make may have a different meaning. Always confirm the code's definition against the vehicle's service information for the specific make and model under test.

Code Information

DTC P16A4 is set by the Engine Control Module (ECM) during the initial SCR system filling or priming test, typically carried out after ignition on, following repairs, or after AdBlue (DEF) tank empty conditions. The fault is logged when the ECM commands the SCR dosing system to perform the first fill operation but does not detect the expected pressure rise, flow response, or system state change within a calibrated time. This indicates that the SCR system is unable to correctly prime or pressurise, preventing accurate AdBlue dosing for NOx reduction. When the code is set, the driver may see an ...

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