P2043

Temperature Sensor Circuit Range/Performance

P2043 is a generic OBD-II powertrain diagnostic trouble code: Temperature Sensor Circuit Range/Performance. 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
P2043
Group
Powertrain
System
Powertrain
Severity
Warning (MIL on)
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What P2043 means

P2043 is stored when the ECM or SCR control module detects that the voltage on the reductant tank heater control circuit is higher than the expected maximum when the heater is commanded off. A high-circuit condition on a heater control line typically indicates a short to the supply voltage, a failed control module driver that cannot pull the line low, or a wiring fault that is holding the circuit at battery or ignition voltage.

The reductant tank heater is used to thaw frozen DEF fluid in cold climates. DEF freezes at approximately -11 degrees Celsius, and the heater ensures the system can dose normally after cold soaks. The ECM controls the heater via a relay or direct driver output and monitors the circuit state to confirm proper operation.

With a high-circuit fault, the heater may be permanently energized or the control signal may be stuck high, potentially causing the heater to overheat the DEF fluid or fail to turn off correctly. Prolonged overheat can degrade the urea solution. This code does not typically cause immediate drivability symptoms but should be diagnosed to prevent DEF fluid degradation and heater element damage.

Common causes

Most-frequently reported root causes when P2043 is logged.

  • 1
    Short to voltage on the heater control wire between ECM/module and relay or heater element.
  • 2
    Failed heater relay stuck in the closed position.
  • 3
    ECM or SCR module output driver fault causing the control line to remain high.
  • 4
    Wiring harness damage resulting in contact with a powered circuit.
  • 5
    Corroded or contaminated relay socket holding contact closed.
  • 6
    Incorrect relay installed with wrong normally-open/normally-closed configuration.
  • 7
    Water intrusion into the control module causing driver output fault.

Symptoms drivers notice

MIL illuminated.
DEF or SCR system warning may be present.
Heater may remain on longer than expected, potentially overheating DEF in warm conditions.
No immediate drivability impact.
Possible DEF fluid discoloration or degradation from prolonged overheating.

How to diagnose P2043

A typical diagnostic flow when this code is present.

  1. 1
    Retrieve all DTCs and note freeze frame conditions, particularly ambient temperature at time of fault.
  2. 2
    Inspect the heater control circuit wiring for shorts to voltage or contact with power wires.
  3. 3
    Check the heater relay -- remove it and verify the control circuit voltage drops as expected.
  4. 4
    Test the relay coil and contact operation on the bench.
  5. 5
    Measure the ECM/module heater driver output voltage with relay removed; it should be low when heater is commanded off.
  6. 6
    Repair any wiring shorts found, or replace the relay if it is stuck closed.
  7. 7
    If ECM driver output stays high with relay removed and no wiring fault found, suspect the control module.

Vehicles where we've handled P2043

Platforms in our catalogue with confirmed P2043 coverage.

AUDI A4 20D

Related powertrain codes

Frequently asked questions

Can P2043 cause DEF fluid to boil or degrade?

Prolonged heater operation in warm ambient conditions can elevate DEF temperature, potentially accelerating urea breakdown, though modern systems have thermal protections to limit this.

Is P2043 a cold weather fault?

Not exclusively -- while the heater is most active in cold weather, the high-circuit fault can occur any time the control circuit develops a short to voltage regardless of temperature.

Is the DEF heater a separate serviceable part?

It depends on the vehicle. Some systems have a standalone heater element; others integrate heating into the DEF pump module, requiring module replacement.

Can I drive normally with P2043?

Yes in most cases, but the underlying issue should be repaired to prevent heater damage and DEF fluid degradation.

Disabling P2043 in software

RaceTune can permanently disable P2043 — 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 P2043 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 EDC17C60 verified 2 software versions
  • Bosch EDC17C74 verified 1 software version
  • Bosch MD1CP004 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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