P2B82

Reductant Injection Quantity Too High Bank 1

P2B82 is a generic OBD-II powertrain diagnostic trouble code: Reductant Injection Quantity Too High Bank 1. It is logged by the engine control unit when the powertrain monitor detects that a specific fault threshold has been exceeded — typically resulting in the malfunction-indicator lamp (MIL / check-engine light) being illuminated.

Code
P2B82
Group
Powertrain
System
Powertrain
Severity
Warning (MIL on)
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What P2B82 means

P2B82 is set when the ECM determines that the actual reductant quantity being delivered on bank 1 is consistently exceeding the commanded target. Over-dosing occurs when more urea is injected than the SCR catalyst can consume for NOx reduction, which leads to ammonia slip: unreacted ammonia passing through the catalyst and into the atmosphere. The ECM detects this condition through downstream NOx and, where fitted, ammonia sensor signals combined with its dosing model.

Common causes include a leaking or stuck-open dosing injector that cannot fully close between dose events, a pressure regulator fault holding delivery pressure above target, or a faulty dosing control loop in the ECM calibration. A downstream NOx sensor fault that reports artificially low NOx can also cause the ECM to increase dosing beyond the actual requirement, triggering this code.

Over-dosing is not merely an emissions compliance issue. Excess ammonia can contaminate downstream aftertreatment components such as diesel oxidation catalysts (DOC) and particulate filters (DPF), and can produce a noticeable ammonia odour at the tailpipe. Prompt diagnosis and repair are recommended.

Common causes

Most-frequently reported root causes when P2B82 is logged.

  • 1
    Stuck-open or leaking reductant dosing injector unable to fully stop flow.
  • 2
    Reductant pressure regulator fault holding system pressure above the target value.
  • 3
    Faulty downstream NOx sensor reporting artificially low NOx, causing the ECM to over-dose.
  • 4
    ECM dosing control loop fault commanding excessive injector duty cycle.
  • 5
    Injector return check valve failure allowing continuous drip-through.
  • 6
    DEF concentration higher than nominal, delivering more urea per volume dosed.
  • 7
    Dosing control calibration error following an incorrect software update.

Symptoms drivers notice

MIL illuminated.
SCR or emissions warning lamp active.
Ammonia odour detectable at the tailpipe.
Possible ammonia slip detection if a downstream ammonia sensor is fitted.
Elevated ammonia readings during tailpipe emissions inspection.
Potential degradation of DOC or DPF performance from ammonia contamination.

How to diagnose P2B82

A typical diagnostic flow when this code is present.

  1. 1
    Read all DTCs and check for companion downstream NOx sensor or pressure regulation codes.
  2. 2
    Monitor live reductant system pressure and compare to commanded pressure specification.
  3. 3
    Monitor bank 1 downstream NOx sensor live data for plausibly low readings that could indicate sensor fault.
  4. 4
    Check the dosing injector for a stuck-open condition by monitoring pressure bleed-off with the injector de-energised.
  5. 5
    Verify ECM commanded dose rate versus actual pressure response to identify dosing loop faults.
  6. 6
    Check DEF concentration if recently refilled from an unfamiliar source.
  7. 7
    Inspect downstream aftertreatment components for ammonia contamination if over-dosing has been prolonged.

Vehicles where we've handled P2B82

Platforms in our catalogue with confirmed P2B82 coverage.

BMW 320D
2016

Related powertrain codes

Frequently asked questions

Is ammonia smell at the exhaust always caused by P2B82?

An ammonia odour is a strong indicator of over-dosing or ammonia slip, and P2B82 is a likely cause. However, it can also occur transiently during normal cold-start rich-dosing strategies on some systems.

Can P2B82 damage the catalytic converter?

Prolonged ammonia over-dosing can contaminate the DOC and reduce its efficiency. In severe or sustained cases, catalyst substrate damage is possible.

Will clearing the code fix the over-dosing problem?

No. The underlying cause (stuck injector, faulty sensor, pressure regulator fault) must be corrected. Clearing the code without repair will result in the code returning.

Can a software calibration error cause P2B82?

Yes. An incorrect dosing map following an ECM software update can cause systematic over-dosing. Check for relevant technical service bulletins if no hardware fault is found.

Disabling P2B82 in software

RaceTune can permanently disable P2B82 — and any other OBD-II diagnostic trouble code — on every ECU family we support. The monitor is disabled inside the ECU itself, so the fault stops being logged: the warning light stays off and the engine never enters limp mode for this code. The change is tied to your exact software version.

Permanent
The monitor is disabled in the ECU itself — not just cleared. It cannot return.
Tailored to your file
Each patch is matched to your specific software version — never a one-size-fits-all file.
Reversible
The original file is always preserved. Reflash the stock to return the ECU to factory state.

ECUs with a P2B82 disable in our catalogue

Confirmed coverage from our recipe database — we support many more families. Upload your file and our identifier will match it automatically.

  • Bosch EDC17C50 verified 1 software version

Software modifications affect emissions compliance and are not road-legal in many jurisdictions. RaceTune service files are intended for motorsport, off-road, and export use.

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