U010B

Lost Communication With Exhaust Gas Recirculation Control Module B

U010B is a generic OBD-II network diagnostic trouble code: Lost Communication With Exhaust Gas Recirculation Control Module B. It is logged by the engine control unit when the egr monitor detects that a specific fault threshold has been exceeded — typically resulting in the malfunction-indicator lamp (MIL / check-engine light) being illuminated.

Code
U010B
Group
Network
System
EGR
Severity
Warning (MIL on)
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What U010B means

U010B indicates that the ECM or PCM has lost serial data bus communication with a second Exhaust Gas Recirculation Control Module, designated Module B. This code appears on vehicles equipped with more than one electronically controlled EGR node, such as engines using dual EGR circuits (for example separate high-pressure and low-pressure EGR paths) where each path has its own control module reporting position and flow over the CAN bus.

The detection logic mirrors that of U010A: the controlling module awaits a periodic message from the EGRCM-B node and sets U010B when that message is absent beyond the calibration timeout. Because the 'B' designation identifies the second instance of the component, the primary EGR circuit may remain functional and the ECM will typically apply a backup strategy, so the engine generally continues to run with the MIL illuminated rather than failing outright.

The most common root cause is a circuit fault interrupting power or ground to the EGRCM-B node, or an open or short on the shared data bus. A wiring fault on common bus sections can set both U010A and U010B together; if both are present, inspect shared wiring first. Confirm which physical module is designated 'B' for the specific vehicle before diagnosis.

Common causes

Most-frequently reported root causes when U010B is logged.

  • 1
    Open or short on the data bus segment serving the secondary EGR control module (Module B).
  • 2
    Loss of power or ground supply to the EGRCM-B node.
  • 3
    Blown fuse feeding the EGRCM-B module.
  • 4
    Corroded or damaged connector terminals at the EGRCM-B harness connector.
  • 5
    Failed EGRCM-B module hardware.
  • 6
    Shared wiring fault that simultaneously disrupts both EGRCM-A and EGRCM-B communication.
  • 7
    Incorrect module configuration or programming after a replacement.

Symptoms drivers notice

MIL illuminated with U010B stored.
Secondary EGR circuit operation disabled with the ECM running a backup strategy.
Scan tool unable to communicate with the EGRCM-B node.
U010A may be stored alongside U010B if the fault affects the common bus.
Possible companion EGR flow or position DTCs for the affected circuit.

How to diagnose U010B

A typical diagnostic flow when this code is present.

  1. 1
    Record all DTCs and freeze-frame data with a scan tool before any clearing.
  2. 2
    Identify which physical module is designated EGRCM-B for the specific vehicle using the service manual.
  3. 3
    Verify battery voltage, ignition-switched supply, and ground at the EGRCM-B connector.
  4. 4
    Check bus termination resistance on the segment serving EGRCM-B to detect opens or shorts.
  5. 5
    Inspect the harness for damage, heat, and vibration wear along its routing.
  6. 6
    Confirm whether EGRCM-B appears on the bus using scan tool network node diagnostics.
  7. 7
    If wiring and power are confirmed good, substitute the EGRCM-B module and retest.

Related network codes

Frequently asked questions

What does the 'B' suffix mean in U010B?

In SAE J2012 nomenclature the 'B' suffix denotes the second instance of the same component type, here a second EGR control module. Its exact physical location and role vary by manufacturer.

Can U010B set without U010A?

Yes. If only the secondary EGRCM-B circuit has a fault, U010B will set while U010A remains clear, confirming the primary EGR control module is still communicating normally.

Is the repair procedure the same as for U010A?

The general approach is identical, check power, ground, and bus wiring before replacing the module, but you must locate the correct EGRCM-B connector and harness path for the specific vehicle.

Will U010B affect my emissions test?

Yes. Because U010B is a network communication code affecting an emissions system it will illuminate the MIL, causing a failure on any OBD-II inspection that checks for active DTCs or a lit MIL.

Disabling U010B in software

RaceTune can permanently disable U010B — 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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