Skip to content

P2048 – Reductant Injector Circuit Low Bank 1 Unit 1 (OBD2)

P2048 means "Reductant Injector Circuit Low Bank 1 Unit 1". The voltage the control unit measures in the SCR AdBlue system circuit is below the permitted minimum. For a sensor this usually means the signal wire is shorted to ground or the reference voltage is missing; for an actuator, that its control wire is shorted to ground.

Last updated

P2048 quick summary

Fault codeP2048
MeaningReductant Injector Circuit Low Bank 1 Unit 1
SystemPowertrain (Engine & Transmission)
VehiclesGeneric OBD2
SeverityHigh
Can I drive?For a limited distance. Watch the dashboard: many vehicles count down and then limit power or prevent restarting. Top up AdBlue if it is low and have faults repaired before the countdown ends.
Repair cost€0 – €2,000

How the SCR (AdBlue) system works

The SCR system injects AdBlue (urea solution) into the exhaust to convert nitrogen oxides into nitrogen and water; these codes mean a fault in the AdBlue level, pressure, injector, heater or the system's efficiency.

AdBlue is stored in a separate tank with a level sensor, a heater and a pump. The pump builds pressure and the dosing injector sprays AdBlue into the exhaust before the SCR catalyst. NOx sensors before and after the catalyst tell the control unit how much to inject and whether the catalyst works.

By law the vehicle must warn the driver and, if the fault is not fixed, limit the engine or prevent a restart after a countdown. Codes cover a low AdBlue level, level sensor faults, low pressure, injector circuit faults, low catalyst efficiency and NOx emissions above the limit.

Typical causes are crystallised AdBlue blocking the injector or lines, a failed pump or tank heater (often in the tank unit), poor-quality or diluted AdBlue, faulty NOx sensors and wiring faults.

Bank 1 is the side of the engine that contains cylinder 1. In-line engines (three, four, five or six cylinders in a row) have only bank 1.

Symptoms of P2048

  • AdBlue / emission warning and countdown message
  • Check Engine light
  • Engine will not restart after the countdown
  • Reduced power
  • AdBlue consumption too high or too low

Most common causes of P2048 (most likely first)

Mechanic's Pro Tip

Never add water or anything other than ISO 22241 AdBlue to the tank. Contaminated AdBlue can destroy the pump, injector and catalyst – the repair then costs far more than a new tank of fluid.

  1. 1.Signal or control wire shorted to ground

    Most likely

    Look for chafed insulation where the harness touches the engine, exhaust brackets or body edges.

  2. 2.Missing 5 V reference or supply voltage

    An open reference wire or a shorted sensor elsewhere on the same reference circuit can pull it down.

  3. 3.Internal short in the SCR AdBlue system

  4. 4.AdBlue level too low or poor-quality AdBlue

  5. 5.Crystallised AdBlue in the injector or lines

    White deposits block the dosing injector or pipes.

  6. 6.Failed AdBlue pump, heater or level sensor

    On many vehicles these are integrated in one tank unit.

  7. 7.Faulty NOx sensor

    Wrong NOx readings make the system dose wrongly and set efficiency codes.

Step-by-step diagnostic guide

  1. 1

    Check AdBlue level and quality

    Top up with ISO 22241 AdBlue if low. If contamination or dilution is suspected, check the concentration with a refractometer.

    Multimeter: Correct AdBlue concentration is about 32.5 % urea.

  2. 2

    Measure the signal voltage

    With the ignition on and the SCR AdBlue system plugged in, back-probe the signal wire. Then unplug it and check the reference/supply and ground wires separately.

    Multimeter: Signal near 0 V = short to ground or no reference. Reference wire: about 5 V with ignition on. Signal wire to ground with connector unplugged: no continuity.

  3. 3

    Read codes and live data

    Read all codes and check AdBlue level, pressure, temperature and both NOx sensor readings in live data.

  4. 4

    Run the dosing and pressure tests

    Use the scan tool's AdBlue pump and dosing quantity tests to check pressure build-up and the injected amount.

  5. 5

    Inspect injector and lines

    Check the dosing injector and lines for white crystals and leaks; check the tank unit connector.

  6. 6

    Repair and reset

    Clean or replace the injector, pump/tank unit or sensor, clear codes and run the SCR system adaptation; some vehicles need the countdown reset with a scan tool.

Frequently asked questions

Can I keep driving with P2048?

For a limited distance. Watch the dashboard: many vehicles count down and then limit power or prevent restarting. Top up AdBlue if it is low and have faults repaired before the countdown ends.

How much does it cost to fix P2048?

Typical repair costs are 0 € – 2000 €, depending on the cause and the vehicle. The most common fixes are: signal or control wire shorted to ground; missing 5 V reference or supply voltage; internal short in the SCR AdBlue system. Always confirm the cause with the tests above before buying parts.

Why won't my car start after an AdBlue warning?

The law requires the engine to be disabled if an AdBlue fault is not fixed within a certain distance. Fix the fault and clear the codes; some vehicles need a scan tool to reset the countdown.

Can I just remove or disable the AdBlue system?

No. It is illegal for road vehicles, the car fails inspection and may lose its type approval.

What is the difference between P2048 and similar codes?

P2048 belongs to a group of codes for the same component that differ in the type or location of the fault: P203E – Reductant Level Sensor Circuit Intermittent; P203F – Reductant Level Too Low; P2047 – Reductant Injector Circuit/Open Bank 1 Unit 1; P2049 – Reductant Injector Circuit High Bank 1 Unit 1; P20E8 – Reductant Pressure Too Low; P20EE – SCR NOx Catalyst Efficiency Below Threshold Bank 1. The tests on this page apply to the whole group; the type of fault tells you where to start.

Related fault codes

This guide is for information only. Working on vehicles can be dangerous — if you are unsure, have the car checked by a qualified mechanic. Values can differ between model years; always check the manufacturer's repair information.