P22FD

Fuel Injector Group A Supply Voltage Circuit Low

P22FD is a generic OBD-II powertrain diagnostic trouble code: Fuel Injector Group A Supply Voltage Circuit Low. 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
P22FD
Group
Powertrain
System
Powertrain
Severity
Warning (MIL on, possible limp mode)
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What P22FD means

DTC P22FD is stored when the PCM detects a lower-than-expected voltage on the supply rail feeding fuel injector group A. Modern gasoline direct injection (GDI) and common-rail diesel systems use a high-voltage boost circuit to supply the injector drivers; port injection systems use battery voltage. Group A designates the first bank or set of injectors in a split-bank or sequenced driver arrangement.

A low supply voltage condition can result from a failing injector driver boost circuit, excessive current draw caused by a shorted injector or wiring harness fault, a weak supply fuse or relay, or high resistance in the supply wiring. If the injector supply voltage drops below threshold, the PCM may be unable to open the injectors reliably, leading to misfires, rough running, and in severe cases an inability to start the engine.

Technicians should begin diagnosis by checking the injector supply fuse and relay before moving to wiring resistance checks and individual injector resistance measurements to locate a shorted element pulling the supply low.

Common causes

Most-frequently reported root causes when P22FD is logged.

  • 1
    Short to ground in the injector group A supply wiring harness.
  • 2
    Shorted fuel injector in group A pulling the supply rail low.
  • 3
    Failed or weak injector driver boost module.
  • 4
    Blown or high-resistance fuse in the injector A supply circuit.
  • 5
    Failed relay or power distribution component for the injector group A supply.
  • 6
    Corroded or high-resistance connector on the injector supply circuit.
  • 7
    PCM internal driver failure affecting the group A supply output.

Symptoms drivers notice

MIL illuminated with P22FD and possibly injector-specific misfire codes.
Engine misfire or rough running affecting cylinders in injector group A.
Hard start or extended cranking due to insufficient injector operation.
Possible entry into limp mode with limited RPM or load.
Fuel odor in some cases if injectors are stuck partially open due to voltage irregularity.

How to diagnose P22FD

A typical diagnostic flow when this code is present.

  1. 1
    Retrieve all DTCs and note any cylinder-specific misfire codes that indicate which injectors are affected.
  2. 2
    Check the fuse and relay for the injector group A supply circuit.
  3. 3
    Measure supply voltage at the injector group A connector with the engine running and compare to specification.
  4. 4
    Disconnect each injector in group A individually and measure coil resistance to identify a shorted injector.
  5. 5
    Inspect the supply wiring harness for chafing or shorts, particularly near heat sources or engine movement points.
  6. 6
    Test the injector driver module or PCM output for correct supply regulation if wiring and injectors are within spec.
  7. 7
    Replace faulty injectors, repair wiring, or replace the driver module as identified, then verify with a drive cycle.

Vehicles where we've handled P22FD

Platforms in our catalogue with confirmed P22FD coverage.

MB GLC220 21D
2017
MB GLE350 30D

Related powertrain codes

Frequently asked questions

Can one shorted injector cause P22FD for the entire group?

Yes. On systems where multiple injectors share a common supply rail, a single shorted injector can pull the entire group A supply voltage below threshold and set P22FD.

What is the difference between P22FD and a cylinder misfire code?

P22FD is a supply circuit fault affecting the entire injector group, while individual misfire codes such as P0301 identify a specific cylinder. Both can be present simultaneously.

Does P22FD affect only GDI engines?

No. The code can apply to any multi-cylinder engine with grouped injector driver circuits, including port injection and diesel common-rail systems, wherever the PCM monitors the injector supply voltage by group.

Is it safe to drive with P22FD active?

Driving is not recommended. Loss of injection on one group of cylinders can cause significant misfires, catalytic converter damage from raw fuel, and potential engine damage from irregular combustion.

Disabling P22FD in software

RaceTune can permanently disable P22FD — 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 P22FD 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 EDC17CP57 verified 2 software versions
  • Bosch EDC17C66 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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