P2151

Injector Group B Supply Voltage Circuit High

P2151 is a generic OBD-II powertrain diagnostic trouble code: Injector Group B Supply Voltage Circuit High. It is logged by the engine control unit when the fuel/inj monitor detects that a specific fault threshold has been exceeded — typically resulting in the malfunction-indicator lamp (MIL / check-engine light) being illuminated.

Code
P2151
Group
Powertrain
System
Fuel/Inj
Severity
Warning (MIL on, possible limp mode)
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What P2151 means

P2151 is the complement to P2150 and is set when the PCM detects that the supply voltage on injector group A is above the expected upper threshold. An excessively high supply voltage can damage injector driver circuits and the injectors themselves, so the PCM monitors for this condition to protect the system.

A high supply voltage condition on an injector group circuit is less common than a low voltage fault, but it can result from a short to a higher voltage supply line, a failed voltage regulator within the driver circuit, or a wiring fault that connects the group A supply rail to a higher-potential circuit. It may also appear as a diagnostic artifact if the monitoring circuit loses its reference.

Diagnosis requires verifying the actual supply voltage at the injector group A circuit under operating conditions and comparing it to specification. Identifying the source of the excess voltage involves checking for unintended connections to higher voltage sources and verifying the integrity of any voltage regulation components in the driver circuit.

Common causes

Most-frequently reported root causes when P2151 is logged.

  • 1
    Short to a higher voltage supply line on the injector group A supply circuit.
  • 2
    Failed voltage regulation within the PCM injector driver causing an over-voltage condition.
  • 3
    Wiring harness damage creating an unintended connection to a higher potential circuit.
  • 4
    Injector group A relay stuck closed or failed, causing an unregulated supply.
  • 5
    Incorrect wiring repair introducing a voltage source with higher output than specified.
  • 6
    PCM internal fault affecting the group A supply monitor reference.
  • 7
    Charging system over-voltage elevating all supply rails above threshold.

Symptoms drivers notice

MIL illuminated, possibly with other injector or fuel system codes.
Rough running or irregular fuel delivery.
Potential injector or driver circuit damage if condition persists.
Engine may enter a protective reduced-power mode.
Companion codes for injector circuit performance may be present.

How to diagnose P2151

A typical diagnostic flow when this code is present.

  1. 1
    Scan for all DTCs and document freeze frame data.
  2. 2
    Measure actual supply voltage at the injector group A connector under key-on conditions.
  3. 3
    Check charging system voltage to rule out system-wide over-voltage.
  4. 4
    Inspect the group A supply circuit for any unintended connections to higher voltage sources.
  5. 5
    Check relay and fuse integrity for the group A supply circuit.
  6. 6
    Inspect PCM injector driver connector for wiring errors or contact with adjacent circuits.
  7. 7
    Repair any identified wiring faults and verify voltage returns to normal before returning the vehicle to service.

Related powertrain codes

Frequently asked questions

Can an overcharging alternator cause P2151?

Yes. If the charging system voltage is significantly elevated, all supply circuits including the injector group rail can exceed their upper thresholds, triggering high circuit codes across multiple systems.

Is P2151 dangerous to the injectors?

Sustained over-voltage can stress injector solenoid windings and driver transistors. The PCM may disable the group to protect components if the over-voltage condition is severe enough.

How is P2151 diagnosed differently from P2150?

P2150 requires checking for low voltage, open circuits, and failed relays. P2151 requires looking for voltage sources that are too high, such as shorts to power, relay failures causing unregulated supply, or charging system faults.

Will clearing the code fix P2151?

No. The code will return if the over-voltage condition still exists. The source of the excess voltage must be identified and corrected before the code will stay clear.

Disabling P2151 in software

RaceTune can permanently disable P2151 — 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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