P2672

Reductant Heater A Control Circuit High

P2672 is a generic OBD-II powertrain diagnostic trouble code: Reductant Heater A Control Circuit High. 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
P2672
Group
Powertrain
System
Powertrain
Severity
Warning (MIL on)
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What P2672 means

P2672 is stored when the powertrain control module (PCM) or diesel exhaust fluid (DEF) control module detects a higher-than-expected voltage on the control circuit for reductant heater A. This heater is responsible for warming the DEF (urea solution) in the tank or supply lines to prevent freezing in cold ambient conditions.

When the circuit voltage remains high even when the module commands the heater off, the module flags this code and may disable the heater circuit to prevent damage. This typically points to a short to voltage in the wiring harness, a failed heater relay stuck closed, or an internal module fault.

Although the SCR system may continue to operate in mild climates, cold-weather operation without a functional DEF heater risks DEF freezing and subsequent NOx aftertreatment failure. Prolonged operation with this fault can lead to SCR efficiency codes and eventual torque derate if emissions compliance cannot be confirmed.

Common causes

Most-frequently reported root causes when P2672 is logged.

  • 1
    Short to voltage in the reductant heater A control circuit wiring.
  • 2
    Reductant heater relay stuck in the closed (energized) position.
  • 3
    Failed or shorted reductant heater element drawing excessive current.
  • 4
    Corroded or damaged connector pins at the heater or control module.
  • 5
    Internal PCM or DEF control module fault affecting the heater driver circuit.
  • 6
    Aftermarket wiring modifications creating an unintended voltage path.

Symptoms drivers notice

MIL (Check Engine light) illuminated.
DEF heater inoperative or continuously energized.
DEF may freeze in very cold conditions, triggering additional SCR fault codes.
Possible torque derate warning if secondary SCR efficiency codes are also set.
No noticeable driveability change in mild ambient temperatures.

How to diagnose P2672

A typical diagnostic flow when this code is present.

  1. 1
    Connect a scan tool and record all stored and pending DTCs along with freeze frame data.
  2. 2
    Inspect the reductant heater A control circuit wiring and connectors for chafing, melting, or corrosion.
  3. 3
    With the key on and heater commanded off by the scan tool, measure voltage on the heater control line; voltage present indicates a short to power.
  4. 4
    Test the reductant heater relay for proper operation and verify it opens when de-energized.
  5. 5
    Measure resistance of the reductant heater element and compare to specification.
  6. 6
    Inspect the DEF module connector and perform a wiggle test while monitoring live data.
  7. 7
    If wiring and relay are confirmed good, suspect and test the DEF control module or PCM per OEM procedure before replacement.

Vehicles where we've handled P2672

Platforms in our catalogue with confirmed P2672 coverage.

BMW 320D
2016

Related powertrain codes

Frequently asked questions

Can I drive with P2672 active?

Short-term driving is generally possible in mild climates, but the DEF heater will not function correctly. In freezing temperatures the DEF may solidify, causing additional faults and potential torque derate.

Will clearing the code make it go away permanently?

No. If the underlying circuit fault (short to voltage, stuck relay) is not repaired the code will return within one drive cycle once the module re-tests the circuit.

Does P2672 affect fuel economy?

Not directly. However, if the SCR system becomes ineffective due to frozen DEF the ECM may eventually impose a derate that reduces power and could indirectly affect economy.

Is P2672 always a wiring problem?

Usually yes, but a failed relay or a shorted heater element can also set this code. Always verify the circuit externally before condemning the control module.

Disabling P2672 in software

RaceTune can permanently disable P2672 — 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 P2672 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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