P026D

Fuel Injector Group B Supply Voltage Circuit Low

P026D is a generic OBD-II powertrain diagnostic trouble code: Fuel Injector Group B 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
P026D
Group
Powertrain
System
Powertrain
Severity
Warning (MIL on, possible limp mode)
Need P026D disabled?
RaceTune permanently disables any OBD-II trouble code on supported ECUs — for motorsport, off-road, and export use.
→

What P026D means

P026D is the Group B counterpart to P026C and indicates that the PCM has detected a low voltage condition on the supply circuit powering injector Group B. The same diagnostic logic applies: the PCM monitors the high-side supply rail for each injector group and flags a low voltage fault when the Group B rail falls below the acceptable threshold.

On V-type engines, Group B commonly supplies the injectors on Bank 2, making this fault particularly impactful as it disables fueling on an entire bank. The result is severe misfires, rough running, increased vibration, and potentially a no-start condition. The catalytic converter on Bank 2 may also be at risk if raw fuel is present in the exhaust from Group B cylinders that are cranking without firing.

As with Group A, the diagnostic approach is circuit-first: verify fuse and relay integrity, test supply voltage at the injector harness connector, and inspect wiring before suspecting individual injectors or the PCM. Concurrent misfire codes for specific cylinders will help confirm which bank is affected and guide the technician to the correct wiring harness section.

Common causes

Most-frequently reported root causes when P026D is logged.

  • 1
    Blown fuse on the Group B injector supply circuit.
  • 2
    Failed injector supply relay for Group B.
  • 3
    Short to ground in the Group B injector supply wiring harness.
  • 4
    Corroded or loose connector on the Group B injector supply circuit.
  • 5
    Internal short within one or more Group B injectors pulling down the supply voltage.
  • 6
    Wiring damage from heat or mechanical abrasion near the exhaust on Bank 2.

Symptoms drivers notice

MIL illuminated.
Misfires on all cylinders fueled by injector Group B.
Severe engine vibration from running on Group A cylinders only.
Possible no-start if Group B supplies a critical bank.
Risk of catalytic converter damage from unburned fuel in the exhaust.
Additional misfire DTCs for Group B cylinders.

How to diagnose P026D

A typical diagnostic flow when this code is present.

  1. 1
    Retrieve all DTCs and record misfire codes to confirm Group B cylinder involvement.
  2. 2
    Inspect the Group B injector supply fuse and test for continuity.
  3. 3
    Check the Group B injector supply relay for proper operation.
  4. 4
    Measure supply voltage at the Group B injector harness connector with ignition on.
  5. 5
    Inspect the wiring harness from fuse/relay to Group B injector connectors for shorts to ground or physical damage.
  6. 6
    Disconnect Group B injectors individually to check whether a single injector short is pulling down the supply rail.
  7. 7
    Verify PCM output driver integrity after confirming the external circuit is sound.

Related powertrain codes

Frequently asked questions

Can P026D damage the catalytic converter?

Yes. If Group B cylinders are cranking without firing, unburned fuel enters the exhaust and can overheat and damage the catalytic converter. Prompt repair is advisable.

How do I differentiate P026C from P026D fault location?

P026C affects Group A (typically Bank 1 on V-engines) and P026D affects Group B (typically Bank 2). Use misfire codes and wiring diagrams to confirm which bank is affected.

Can I temporarily bypass the affected injector group?

No. Bypassing injector circuits is not safe and could damage the PCM or cause a fuel delivery hazard. Diagnose and repair the circuit fault properly.

Is this code common after engine harness repairs?

Yes. Improper harness repairs that inadvertently short injector supply wires to ground can trigger this code. Always inspect repair areas in the harness when this code appears after recent work.

Disabling P026D in software

RaceTune can permanently disable P026D — 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.

Got P026D in your scan?

Upload your ECU file — we'll identify the exact software version and confirm whether a disable is available for your car.

Upload your file