P0261 — Cylinder 1 Injector A Circuit Low

The injector A electrical monitor for cylinder 1 detects a low condition. Its precise meaning depends on driver design; this does not automatically mean low flow or pressure.

Affected system: Powertrain

Symptoms

• Rough idle, misfire or vibration if cylinder injection is interrupted.
• Engine warning lamp; reduced power or hard starting depending on affected cylinders.

Possible causes

• Loose connector, damaged terminals or open/shorted wiring for cylinder 1.
• Injector electrical fault or, less commonly, driver fault; a shared supply problem can affect multiple cylinders.

What to check

• Confirm cylinder numbering and injector type; identify the circuit for cylinder 1 on the diagram rather than assuming location.
• Save codes and failure conditions; if several injectors are affected, check shared supplies/connections first.
• Inspect connector and wiring for cylinder 1, including terminal retention and vibration/chafing areas.
• Test shorts and supply in the subcode-identified circuit; low may describe driver diagnostics rather than one wire voltage.
• Test injector and command waveform using compatible equipment and OEM limits; do not apply battery voltage directly, then verify the repair.

Also written as: P0261-00, P026100, PO261 (some scan tools add the fault-type byte, e.g. -00).