OBD-II Fault Code

P1274: Cylinder #4 High To Low Side Open

Meaning, symptoms, likely causes, diagnostic checks and repair guidance for P1274.

System family

Powertrain

Manufacturer-specific

Repair category

Electrical circuit / sensor

Use this category to narrow your checks before replacing parts.

Severity

Medium

Severity is a general guide. Confirm with scan-tool data and vehicle symptoms.

What P1274 usually means

Cylinder #4 High To Low Side Open.

Common symptoms

Check Engine light; Poor drivability or reduced fuel economy depending on fault

Likely causes

Open circuit; Disconnected connector; Broken wire; Failed component; Low signal voltage; Weak power supply; High resistance/poor ground; Failed sensor; High signal voltage; Open ground; Short to voltage

Diagnostic checks

Scan all modules and record freeze-frame data before clearing codes; Check battery voltage and related fuses; Check connector fitment and continuity from module to component; Check sensor reference voltage, ground and signal voltage; Check sensor ground and signal circuit for short to voltage

Repair guidance

Repair open wire/connector or replace the failed component after continuity test; Repair poor ground/power feed or replace confirmed faulty sensor; Repair ground/signal circuit or replace confirmed faulty sensor

Verification after repair

Clear code, road-test through the same drive condition, then rescan

Note: Confirm vehicle make/model/year because manufacturer-specific codes can vary; Manufacturer-specific: confirm definition and test steps in the vehicle service manual. A DTC identifies a circuit or system condition, not always the failed part.