U059E

Invalid Data Received From Auxiliary Heater Control Module

U059E is a generic OBD-II network diagnostic trouble code: Invalid Data Received From Auxiliary Heater Control Module. It is logged by the engine control unit when the network monitor detects that a specific fault threshold has been exceeded — typically resulting in the malfunction-indicator lamp (MIL / check-engine light) being illuminated.

Code
U059E
Group
Network
System
Network
Severity
Warning (MIL on)
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What U059E means

DTC U059E is set when a networked control module detects that data received from the Auxiliary Heater Control Module contains values that are implausible or fail message validation checks. The auxiliary heater is a supplemental fuel-fired or electric heater used in diesel and some hybrid vehicles to provide cabin heat and support engine warm-up, and its control module communicates operational status, faults, and temperature data via the CAN bus.

As a U04xx-pattern code, this indicates the network link to the auxiliary heater module is present but the content of its messages is flagged as invalid. Causes include a degraded or malfunctioning heater control module producing erroneous data frames, software or calibration corruption within the module, wiring faults causing message corruption, or a module mismatch following component replacement without proper vehicle-specific programming.

The receiving module will typically respond to invalid auxiliary heater data by disabling demand-based heater activation or defaulting to a fixed operating mode. In cold climates this can affect cabin comfort and engine warm-up strategy, but it does not typically cause a drivability derate.

Common causes

Most-frequently reported root causes when U059E is logged.

  • 1
    Failing auxiliary heater control module transmitting corrupted or out-of-range data.
  • 2
    CAN bus wiring fault causing message corruption on the auxiliary heater communication segment.
  • 3
    Software corruption or incompatible firmware in the auxiliary heater module.
  • 4
    Intermittent power or ground fault at the auxiliary heater module.
  • 5
    Replacement module not programmed to the vehicle, causing message format mismatches.
  • 6
    Electromagnetic interference corrupting auxiliary heater CAN frames.

Symptoms drivers notice

MIL or climate system warning light illuminated.
Auxiliary heater inoperative or operating in a degraded mode.
Reduced cabin heating performance in cold conditions.
Additional auxiliary heater fault codes may be stored.
Engine warm-up may be slower if the heater assists coolant heating.

How to diagnose U059E

A typical diagnostic flow when this code is present.

  1. 1
    Read all DTCs across all modules to identify the scope of network faults.
  2. 2
    Inspect the auxiliary heater module harness and connector for corrosion or wiring damage.
  3. 3
    Verify auxiliary heater module power and ground supply.
  4. 4
    Attempt direct communication with the auxiliary heater module via scan tool.
  5. 5
    Monitor auxiliary heater live data to assess data plausibility during operation.
  6. 6
    Check for available module software updates or reprogram if a firmware issue is known.
  7. 7
    Replace the auxiliary heater module only after confirming wiring integrity and ruling out bus faults.

Related network codes

Frequently asked questions

What is an auxiliary heater control module?

It is the electronic controller for a supplemental fuel-fired or electric heater that provides cabin warmth and supports engine warm-up, separate from the main HVAC system.

Will U059E disable the main engine coolant system?

No. The auxiliary heater is a supplemental system. The main engine cooling and heating circuits are unaffected, though cabin comfort may be reduced.

Can U059E appear on vehicles without an auxiliary heater?

Typically no, but if a module is expecting auxiliary heater data that was present in a previous vehicle configuration, a missing module could trigger related faults.

Is U059E a safety-critical fault?

It is not safety-critical in terms of vehicle control, but in extreme cold climates where the auxiliary heater is needed for windshield defrost or cabin safety, prompt repair is advisable.

Disabling U059E in software

RaceTune can permanently disable U059E — 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.

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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