P0277

Cylinder 6 Injector Circuit High

P0277 is a generic OBD-II powertrain diagnostic trouble code: Cylinder 6 Injector 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
P0277
Group
Powertrain
System
Fuel/Inj
Severity
Warning (MIL on, possible limp mode)
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What P0277 means

P0277 — Cylinder 6 Injector Circuit High — is triggered when the PCM detects that the voltage present on the cylinder 6 injector control circuit is above the manufacturer-specified maximum. Under normal operation the PCM's internal driver transistor pulls the injector's control wire low (toward ground) each time the injector fires; when that pull-down cannot occur — due to a short to battery voltage in the wiring or an open driver circuit — the line stays high, preventing normal injector operation. The MIL illuminates and a fault snapshot is stored.

The code affects all six-or-more-cylinder OBD-II vehicles: V6, inline-6, V8, V10, and V12 engines all have a cylinder 6. Common vehicles on which this code appears include GM LS-series V8 trucks and SUVs, Ford 4.6/5.4 Modular V8, Mercedes-Benz V6/V8 petrol and diesel engines, Chrysler Hemi V8, and Hyundai/Kia V6 and four-cylinder engines with cylinder 6 wiring routed near heat sources. A high-circuit fault usually means injector 6 is not firing at all, causing cylinder 6 to be fuel-cut, which results in an immediate rough idle, power loss, and potential catalyst contamination from unburned air.

Diagnosis centres on measuring the injector coil resistance (a shorted coil reads near zero ohms and can damage the PCM driver) and tracing the control-side wire for an inadvertent contact with a 12 V source. Because a shorted injector can destroy the PCM driver stage, the injector coil resistance should be measured before the PCM is powered up after any related wiring repair.

Common causes

Most-frequently reported root causes when P0277 is logged.

  • 1
    Short to battery voltage (B+) in the cylinder 6 injector control wire.
  • 2
    Failed injector solenoid coil internally shorted (near-zero resistance), pulling excessive current.
  • 3
    Damaged or melted wiring insulation causing the control wire to contact a power source.
  • 4
    Faulty injector driver transistor inside the PCM holding the circuit high.
  • 5
    Corroded or spread connector pin creating intermittent contact with an adjacent power wire.
  • 6
    Aftermarket accessories or previous wiring repairs incorrectly tapped into the injector harness.
  • 7
    Water or coolant ingress into the injector connector causing tracking between pins.

Symptoms drivers notice

Malfunction Indicator Lamp (MIL) illuminated.
Rough idle and engine shaking from cylinder 6 misfire.
Significant loss of power, especially noticeable under load.
Possible fuel smell or black exhaust smoke if fuel is being dumped unburned.
Companion code P0306 (cylinder 6 misfire) typically stored at the same time.
In severe cases, catalytic converter overheating from raw fuel entering the exhaust.

How to diagnose P0277

A typical diagnostic flow when this code is present.

  1. 1
    Connect a scan tool, record all DTCs and freeze-frame data, and note any companion misfire or fuel-system codes.
  2. 2
    Unplug the cylinder 6 injector connector and measure coil resistance with a DMM; a reading near 0 Ω (shorted coil) means the injector must be replaced before further electrical testing to protect the PCM.
  3. 3
    Inspect the injector harness along its full length for chafed insulation, heat damage, or contact with the battery-positive rail, alternator, or chassis power feeds.
  4. 4
    With the ignition OFF and injector unplugged, use a DMM to check voltage on the PCM control wire relative to chassis ground — any voltage above 0.5 V indicates a short to power in the harness.
  5. 5
    Use a wiring diagram to trace the injector driver circuit back to the PCM; back-probe the PCM pin and verify the driver pulls to near 0 V when commanded on.
  6. 6
    If harness and injector test good, suspect a failed PCM driver stage — confirm with the manufacturer's pinpoint test procedure before replacing the PCM.
  7. 7
    After repair, clear codes and perform a road test; confirm P0277 and P0306 do not return under normal driving conditions.

Related powertrain codes

Frequently asked questions

Can a shorted injector damage the PCM?

Yes. A shorted injector coil (near-zero resistance) allows excessive current through the PCM driver transistor, which can burn out the driver stage. Always measure injector coil resistance before replacing the PCM, and replace a shorted injector before re-energising the circuit.

What is the difference between P0276 (low) and P0277 (high)?

P0276 means the circuit voltage is below the expected minimum, pointing to an open circuit, high resistance, or a failed PCM driver that cannot supply voltage. P0277 means the circuit voltage is above the expected maximum, indicating a short to power or a stuck-open driver. Diagnosis procedures differ significantly between the two.

Is it safe to drive with P0277?

Only for a very short distance if necessary. Cylinder 6 is likely not firing, meaning unburned fuel or air is entering the exhaust. Extended driving risks overheating and destroying the catalytic converter, in addition to continued rough running and power loss.

Will dielectric grease help prevent P0277?

Dielectric grease applied to the injector connector terminals helps exclude moisture and prevent the pin corrosion or tracking that can create intermittent short-to-power conditions. It is a good preventive measure after any connector service, though it will not fix an existing wiring short or shorted injector coil.

Disabling P0277 in software

RaceTune can permanently disable P0277 — 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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