Open or damaged wiring between the PCM and the cylinder 1 fuel injector; Failed cylinder 1 fuel injector (open internal coil); Corroded or loose electrical connector at the injector or PCM; Broken or chafed wire harness near the intake manifold or valve cover; Faulty PCM driver circuit for the injector (rare but possible); Rodent damage to the injector wiring harness

DTC codes / Ford codes / P1271

P1271 · FordCylinder 1 High To Low Side Open

Q: What does code P1271 mean?

Cylinder 1 High To Low Side Open. P1271 on Ford vehicles means the powertrain control module (PCM) has detected an open circuit between the high and low sides of the fuel injector circuit for cylinder 1. The PCM monitors the injector driver circuit and sets this code when the expected current flow is missing, indicating a break in the wiring or a failed injector coil.

P1271 on Ford vehicles means the powertrain control module (PCM) has detected an open circuit between the high and low sides of the fuel injector circuit for cylinder 1. The PCM monitors the injector driver circuit and sets this code when the expected current flow is missing, indicating a break in the wiring or a failed injector coil.

SystemPowertrain

Code typeFord specific

SeverityMedium

Fix difficultyIntermediate

AreaFuel and air metering (injector circuits)

Symptoms you may notice

Illuminated check engine light, often with no other symptoms besides the warning light
Rough idle or misfire felt as a shake or stumble, especially when cold
Noticeable loss of power and reduced fuel economy
Engine may run in limp mode with reduced performance
Hard starting or stalling, particularly when the engine is cold
Possible sulfur or raw fuel smell from the exhaust if the injector is stuck open

Common causes, most likely first

Open or damaged wiring between the PCM and the cylinder 1 fuel injector
Failed cylinder 1 fuel injector (open internal coil)
Corroded or loose electrical connector at the injector or PCM
Broken or chafed wire harness near the intake manifold or valve cover
Faulty PCM driver circuit for the injector (rare but possible)
Rodent damage to the injector wiring harness

How to diagnose and fix it

Inspect the cylinder 1 injector connector for corrosion, looseness, or pushed-out pins
Check the injector coil resistance with a multimeter and compare to the manufacturer's specification
Perform a wiggle test on the injector harness while watching live misfire or injector data
Check for continuity and short-to-ground on the high and low side wires between the injector and PCM
Repair any damaged wiring, replace corroded terminals, and apply dielectric grease
If the injector coil is open, replace the cylinder 1 fuel injector
Clear the code and verify the repair with a road test and live data monitoring

What Ford Techs Check Before Replacing Injectors

A loose or corroded connector at the cylinder 1 injector is far more common than a failed injector itself, so always inspect and clean the terminals before condemning the part.
The code can be set by a chafed wire in the harness where it rubs against the intake manifold or valve cover, so a visual inspection of the entire run is essential.
On some Ford engines, the injector harness is part of the main engine harness and a break inside the loom may only show up during a wiggle test with the engine running.
A failed PCM driver is rare, but if the injector and wiring test good, check for driver operation with a noid light before replacing the computer.
This code does not always mean the injector is dead; a poor ground or low battery voltage can cause the PCM to misreport an open circuit, so verify battery and ground integrity first.

Can I keep driving with P1271?

You can drive a short distance to a repair shop, but avoid heavy acceleration or long trips because the misfire can damage the catalytic converter and reduce engine power. If the engine runs very rough or stalls, stop driving and have it towed.

Tools that help

Tools we recommend are in the Auto Veteran shop on Amazon. As an Amazon Associate we earn from qualifying purchases.

Guidance is general and written for Ford vehicles. Exact tests and values vary by model, so confirm the fault before replacing parts.