Cylinder 1 High to Low Side Open (7.3L Diesel)
Findings, check these first
- Open injector solenoid on cylinder 1
- Broken under-valve-cover harness wire
- Unplugged injector connector
- Failed injector
- IDM driver fault for cylinder 1
Standard procedure
- Run an injector buzz test and note cylinder 1
- Remove the valve cover and inspect the harness
- Test injector resistance
- Check connector seating
- Replace the injector or repair the harness
Code lookup
Type a code above, or start from a symptom or a common code.
Press / to jump to the box. Ford-enhanced powertrain, body, chassis and network codes. Generic P0xxx codes live on OBD Codes List.
Sources and review
Review: checked against the recorded source material.
- OBDII.pro: P1271 Ford definition
live reference page (obdii.pro)
Supports: Ford-family meaning for P1271: Cylinder #1 High To Low Side Open
Fetched directly. obdii.pro is a publisher independent of the engine-codes family.
- P1271 FORD Code: Meaning, Causes, and Symptoms | OBD2 Codes
live reference page (obd2-codes.co)
Supports: Ford meaning for P1271: Cylinder #1 High To Low Side Open
Fetched directly. obd2-codes.co phrasing matches the engine-codes family, so it counts as one publisher.
Last updated 2026-09-05.
Report a correction for P1271. Include your vehicle, the issue and a source if you have one.
Related Fuel/Air Metering codes
- P1131Lack of Upstream HO2S Switch - Sensor Indicates Lean (Bank 1)
- P1151Lack of Upstream HO2S Switch - Sensor Indicates Lean (Bank 2)
- P1233Fuel Pump Driver Module Off-Line
- P1289Cylinder Head Temperature Sensor Signal Greater Than Self-Test Range
- P1299Cylinder Head Over-Temperature Protection Active
- P1100Mass Air Flow Sensor Intermittent