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DTC codes / GM codes / P1274

P1274 · GMInjectors Wired Incorrectly

P1274 on GM vehicles indicates that the engine control module (ECM) has detected an injector circuit that is wired incorrectly, meaning the electrical path to one or more fuel injectors does not match the expected configuration. The ECM monitors injector driver circuits for continuity, resistance, and proper sequencing, and it sets this code when the wiring order or connections deviate from factory specifications.

SystemPowertrain
Code typeGM specific
SeverityMedium
Fix difficultyIntermediate
AreaFuel and air metering (injector circuits)

Symptoms you may notice

  • Illuminated check engine light, often with no other noticeable symptoms
  • Rough idle or misfire, especially if multiple injectors are affected
  • Engine stumble or hesitation during acceleration
  • Poor fuel economy due to incorrect fuel delivery
  • Difficulty starting or extended cranking time
  • Possible rich or lean exhaust smell depending on which injector is miswired

Common causes, most likely first

  1. Injector harness connectors swapped between cylinders during prior repairs
  2. Damaged or chafed injector wiring causing crossed signals
  3. Aftermarket or replacement injector connectors pinned incorrectly
  4. Corrosion or loose terminals in the injector harness
  5. ECM injector driver circuit fault due to internal failure
  6. Improperly installed pigtail repair that reversed polarity
  7. Rodent damage or wire pinching altering injector circuit routing

How to diagnose and fix it

  1. Verify the code with a scan tool and check for any related misfire or injector circuit codes
  2. Inspect the injector harness routing and connectors for signs of swapping, damage, or corrosion
  3. Compare injector connector pinout and wire colors against the factory service information for the specific GM vehicle
  4. Perform a resistance and continuity test on each injector circuit from the ECM connector to the injector
  5. Check for injector driver signals with a noid light or oscilloscope to confirm proper pulsing
  6. Repair or replace damaged sections of the injector harness, ensuring correct pin orientation
  7. Clear the code and perform a road test to verify the repair, rechecking for pending codes

When injector wiring is not the real culprit

  • A swapped injector connector from a previous repair is the most common cause, especially after intake or valve cover work.
  • The code can be set by a single mis-pinned connector even if the engine runs smoothly, so visual inspection of pin orientation is critical.
  • Corroded terminals can mimic a miswired circuit by altering resistance, so always check terminal condition before condemning the harness.
  • An internal ECM driver fault can set P1274 without any harness issue, so testing driver output with a scope is necessary before replacing the ECM.
  • This code is often accompanied by misfire codes for the affected cylinder, but the absence of a misfire does not rule out a wiring error.

Can I keep driving with P1274?

Driving with P1274 is generally safe for short distances, but avoid heavy acceleration or towing until the fault is repaired, as incorrect injector operation can lead to misfires, catalyst damage, or poor fuel economy.

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 GM vehicles. Exact tests and values vary by model, so confirm the fault before replacing parts.

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